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Background: Safety and survival during and after donor nephrectomy (DN) are one of the main concerns in living kidney donors (LKDs). Therefore, kidney (left/right) to be procured should be determined after considering the difficulty of DN, as well as the preservation of remnant renal function (RRF). In this prospective study, we investigated the roles of computed tomography volumetry (CTV) in split renal function (SRF) and established a predictive model for RRF in LKDs., Methods: We assessed 103 LKDs who underwent DN at our institute. The Volume Analyzer SYNAPSE VINCENT image analysis system were used as CTV. RRF was defined as the estimated glomerular filtration rate (eGFR) 12 months after DN. The association between various factors measured by CTV and RRF were investigated, and a role of CTV on prediction for RRF was assessed., Results: The median age and the preoperative eGFR were 58 years and 80.7 mL/min/1.73m 2 , respectively. Each factor measured by CTV showed an association with RRF. The ratio of remnant renal volume to body surface area (RRV/BSA) could predict RRF. In addition, RRV/BSA could predict RRF more accurately when used together with age and 24-h creatinine clearance (CrCl)., Conclusions: Our findings suggest that RRV/BSA measured by CTV can play an important role in predicting RRF, and a comprehensive assessment including age and CrCl is important to determine the kidney to be procured., (© 2021. The Author(s).)

Background: The aim of this longitudinal prospective study was to search if even in the absence of total or partial nephrectomy the kidney size can increase as the kidney function improves., Methods: We randomly enrolled 80 adult patients with various degrees of chronic renal failure but non-dialysis dependent neither totally or partially nephrectomized nor affected by any of the pathological conditions that can increase kidney size. The patients underwent a first examination comprehensive of a blood sample and renal ultrasonography and then were submitted to a therapeutic intervention aimed at removing all nephrotoxic agents to finally be subjected to a last similar medical examination., Results: The statistical analysis displayed a strong positive correlation between the percentage variation of the renal diameters' average and the time changes of the GFR (r 0.731; p < 0.01) as well as the percentage variation of the GFR and the time changes variations of the right (r 0.487; p < 0.01) and left cortical kidney thickness (r 0.519; p < 0.01) and finally a strong negative correlation between the removal of nephrotoxic agents and the percentage variation of the renal diameters' average (r - 0.293; p < 0.01) and the time changes of the GFR (r - 0.429; p < 0.01)., Conclusions: In patients with chronic kidney disease, even in the absence of total or partial nephrectomy, under the stimulus of the removal of any nephrotoxic agents, there may be a limited increase in renal size according to a model that sees them vary according to the changes in GFR.

The thick ascending limb of the loop of Henle (TAL) is the first segment of the distal nephron, extending through the whole outer medulla and cortex, two regions with different composition of the peritubular environment. The TAL plays a critical role in the control of NaCl, water, acid, and divalent cation homeostasis, as illustrated by the consequences of the various monogenic diseases that affect the TAL. It delivers tubular fluid to the distal convoluted tubule and thereby affects the function of the downstream tubular segments. The TAL is commonly considered as a whole. However, many structural and functional differences exist between its medullary and cortical parts. The present review summarizes the available data regarding the similarities and differences between the medullary and cortical parts of the TAL. Both subsegments reabsorb NaCl and have high Na + -K + -ATPase activity and negligible water permeability; however, they express distinct isoforms of the Na + -K + -2Cl - cotransporter at the apical membrane. Ammonia and bicarbonate are mostly reabsorbed in the medullary TAL, whereas Ca 2+ and Mg 2+ are mostly reabsorbed in the cortical TAL. The peptidic hormone receptors controlling transport in the TAL are not homogeneously expressed along the cortical and medullary TAL. Besides this axial heterogeneity, structural and functional differences are also apparent between species, which underscores the link between properties and role of the TAL under various environments.

Objective: To investigate the use of shear wave elastography (SWE)-derived estimates of Young's modulus (YM) as an indicator to detect abnormal renal tissue diagnosed by estimated glomerular filtration rate (eGFR)., Methods: The study comprised 106 chronic kidney disease (CKD) patients and 203 control subjects. Conventional ultrasound was performed to measure the kidney length and cortical thickness. SWE imaging was performed to measure renal parenchymal stiffness. Diagnostic performance of SWE and conventional ultrasound were correlated with serum creatinine, urea levels and eGFR., Results: Pearson's correlation coefficient revealed a negative correlation between YM measurements and eGFR (r = -0.576, p < 0.0001). Positive correlations between YM measurements and age (r = 0.321, p < 0.05), serum creatinine (r = 0.375, p < 0.0001) and urea (r = 0.287, p < 0.0001) were also observed. The area under the receiver operating characteristic curve for SWE (0.87) was superior to conventional ultrasound alone (0.35-0.37). The cut-off value of less or equal to 4.31 kPa suggested a non-diseased kidney (80.3% sensitivity, 79.5% specificity)., Conclusion: SWE was superior to renal length and cortical thickness in detecting CKD. A value of 4.31 kPa or less showed good accuracy in determining whether a kidney was diseased or not. Advances in knowledge: On SWE, CKD patients show greater renal parenchymal stiffness than non-CKD patients. Determining a cut-off value between normal and diseased renal parenchyma may help in early non-invasive detection and management of CKD.

The connective stromal and epithelial compartments of the kidney have regenerative potential and phenotypic flexibility. A few studies have shown that cells appertaining to both compartments can exhibit myoid phenotypes. The purpose of our study was to investigate the myoid pattern of kidney and its association with the kidney niches containing stromal cells/telocytes (SC/TCs). We performed an immunohistochemical study using a panel of endothelial, myoid, mesenchymal and stem/progenitor markers, namely CD31, CD34, CD105 (endoglin), CD117/c-kit, nestin, desmin, α-smooth muscle actin (α-SMA) and the heavy chain of smooth muscle myosin (SMM). We used histologically normal kidney samples, obtained after nephrectomy, from nine adult patients. The capsular SC/TCs had a strong CD34 and partial nestin and CD105 immunopositivity. Subcapsular and interstitial SC/TCs expressed c-kit, nestin, CD105, but also α-SMA and SMM, therefore having a myoid phenotype. The endothelial SC/TCs phenotype was CD31+/CD34+/CD105+/nestin±/SMM±/α-SMA±. All three myoid markers were expressed in periendothelial SC/TCs. We also found a scarce expression of nestin in parietal epithelial cells of Bowman's capsule, and in podocytes. In epithelial cells, we found a positive expression for CD31, CD117/c-kit, desmin, CD34, SMM, and CD105. In epithelial tubular cells, we found a predominant basal expression of the myoid markers (SMM and desmin). In conclusion, myoepithelial tubular cells, myoid endothelial cells and myoid SC/TCs are normal constituents of the kidney., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

This paper introduces a model-based approach for a fully automatic delineation of kidney and cortex tissue from contrast-enhanced abdominal CT scans. The proposed framework, named CorteXpert, consists of two new strategies for kidney tissue delineation: cortex model adaptation and non-uniform graph search. CorteXpert was validated on a clinical data set of 58 CT scans using the cross-validation evaluation strategy. The experimental results indicated the state-of-the-art segmentation accuracies (as dice coefficient): 97.86% ± 2.41% and 97.48% ± 3.18% for kidney and renal cortex delineations, respectively., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objective: To evaluate the clinical application of computed tomography-based measurement of renal cortical volume and split renal volume as a single tool to assess the anatomy and renal function in patients with renal tumors before and after partial nephrectomy, and to compare the findings with technetium-99m dimercaptosuccinic acid renal scan., Methods: The data of 51 patients with a unilateral renal tumor managed by partial nephrectomy were retrospectively analyzed. The renal cortical volume of tumor-bearing and contralateral kidneys was measured using ImageJ software. Split estimated glomerular filtration rate and split renal volume calculated using this renal cortical volume were compared with the split renal function measured with technetium-99m dimercaptosuccinic acid renal scan., Results: A strong correlation between split renal function and split renal volume of the tumor-bearing kidney was observed before and after surgery (r = 0.89, P < 0.001 and r = 0.94, P < 0.001). The preoperative and postoperative split estimated glomerular filtration rate of the operated kidney showed a moderate correlation with split renal function (r = 0.39, P = 0.004 and r = 0.49, P < 0.001). The correlation between reductions in split renal function and split renal volume of the operated kidney (r = 0.87, P < 0.001) was stronger than that between split renal function and percent reduction in split estimated glomerular filtration rate (r = 0.64, P < 0.001)., Conclusions: The split renal volume calculated using computed tomography-based renal volumetry had a strong correlation with the split renal function measured using technetium-99m dimercaptosuccinic acid renal scan. Computed tomography-based split renal volume measurement before and after partial nephrectomy can be used as a single modality for anatomical and functional assessment of the tumor-bearing kidney., (© 2017 The Japanese Urological Association.)

Objective: To evaluate the relationship between renal corticomedullary differentiation, renal cortical thickness and age-related changes with non-contrast-enhanced steady-state free precession(SSFP) magnetic resonance imaging (MRI) and spatially selective inversion recovery(IR) pulse technology as well as its applied value ., Methods: A total of 76 healthy volunteers had been recruited from August 2014 to June 2015 in First Hospital of China Medical University.All volunteers were divided into three groups: 2-40 years old, 41-60 years old, 61-80 years old. All 76 volunteers underwent non-contrast-enhanced steady-state free precession(SSFP) 3.0 T MRI scan using variable inversion times (TIs)(TI=1 000, 1 100, 1 200, 1 300, 1 400, 1 500, 1 600, 1 700 ms). The renal corticomedullary differentiation was observed and the signal intensity of renal cortex and medulla were measured respectively as well in order to calculate renal corticomedullary contrast ratio. Besides, renal cortical thickness and renal size were measured., Results: All 76 volunteers were successfully performed all the sequences of MRI scan, including 152 useful imaging of kidney in total. The renal corticomedullary differentiation was clearly shown in all subjects. There was negative correlation between the optimal inversion time(TI) and age(r=-0.65, P<0.01). Similarly, negative correlation was observed between renal corticomedullary contrast ratio and age(r=-0.35, P<0.01). The mean renal cortical thickness of all subjects was (5.33±0.71)mm and there were statistically significant difference among those different groups, which was negative-related with age(r=-0.79, P<0.01). There was no statistically significant difference between sexuality and renal cortical thickness.Additionally, renal cortical thickness had no statistically significant difference in both sides of kidneys., Conclusion: The renal corticomedullary differentiation is depicted clearly by means of non-contrast-enhanced steady-state free precession MRI with spatially selective inversion recovery pulse technology. The optimal inversion time decreases along with the increase of age. In the meanwhile, the renal cortical thickness could be measured truthfully and accurately.

Objective: To evaluate perinatal body organ apparent diffusion coefficient (ADC) values at postmortem magnetic resonance imaging (PMMR) in order to evaluate postmortem changes., Methods: Postmortem diffusion-weighted imaging (DWI) of the thorax and abdomen were performed with diffusion gradient values b = 0, 500, and 1000 s/mm(2) on 15 foetal and childhood cases (mean 33.3 ± 7.8 weeks gestation) compared to 44 live infants (mean age 75.5 ± 53.4 days). Mean ADC values were calculated from regions of interest (ROIs) for the lungs, liver, spleen and renal cortex, compared to normative live infantile body ADC values of similar gestational age., Results: Mean ADC values were significantly lower in postmortem cases than in normal controls for liver (0.88 10(-3) mm(2)/s ± SD 0.39 vs. 1.13 ± 0.13; p < 0.05) and renal cortex (0.85 ± 0.26 vs. 1.19 ± 0.13; p < 0.05) but not spleen or muscle. Mean lung ADC values were significantly higher than normal controls (1.06 ± 0.18 vs. 0 ± 0; p < 0.001), and there was a significant correlation between postmortem interval and lung ADC (R(2) = 0.55)., Conclusion: Lung PMMR ADC values are related to postmortem interval, making them a potential marker of time since death. Further research is needed to understand the organ-specific changes which occur in the postmortem period., Key Points: • Liver and spleen PM ADC values were lower than controls. • Lung ADC changes correlate with PM interval. • These findings may be useful in medicolegal cases.

Our aim was to prospectively evaluate the feasibility of diffusional kurtosis imaging (DKI) in normal human kidney and to report preliminary DKI measurements. Institutional review board approval and informed consent were obtained. Forty-two healthy volunteers underwent diffusion-weighted imaging (DWI) scans with a 3-T MR scanner. b values of 0, 500 and 1000 s/mm(2) were adopted. Maps of fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (D⊥), axial diffusivity (D||), mean kurtosis (MK), radial kurtosis (K⊥) and axial kurtosis (K||) were produced. Three representative axial slices in the upper pole, mid-zone and lower pole were selected in the left and right kidney. On each selected slice, three regions of interest were drawn on the renal cortex and another three on the medulla. Statistical comparison was performed with t-test and analysis of variance. Thirty-seven volunteers successfully completed the scans. No statistically significant differences were observed between the left and right kidney for all metrics (p values in the cortex: FA, 0.114; MD, 0.531; D⊥, 0.576; D||, 0.691; MK, 0.934; K⊥, 0.722; K||, 0.891; p values in the medulla: FA, 0.348; MD, 0.732; D⊥, 0.470; D||, 0.289; MK, 0.959; K⊥, 0.780; K||, 0.287). Kurtosis metrics (MK, K||, K⊥) obtained in the renal medulla were significantly (p <0.001) higher than those in the cortex (0.552 ± 0.04, 0.637 ± 0.07 and 0.530 ± 0.08 in the medulla and 0.373 ± 0.04, 0.492 ± 0.06 and 0.295 ± 0.06 in the cortex, respectively). For the diffusivity measures, FA of the medulla (0.356 ± 0.03) was higher than that of the cortex (0.179 ± 0.03), whereas MD, D⊥ and D|| (mm(2) /ms) were lower in the medulla than in the cortex (3.88 ± 0.09, 3.50 ± 0.23 and 4.65 ± 0.29 in the cortex and 2.88 ± 0.11, 2.32 ± 0.20 and 3.47 ± 0.31 in the medulla, respectively). Our results indicate that DKI is feasible in the human kidney. We have reported the preliminary DKI measurements of normal human kidney that demonstrate well the non-Gaussian behavior of water diffusion, especially in the renal medulla., (Copyright © 2014 John Wiley & Sons, Ltd.)

Purpose: To assess the feasibility of diffusion tensor imaging (DTI) of normal kidneys and the influence of hydration state., Materials and Methods: Ten healthy volunteers underwent renal DTI after fasting for 12 hours and 4 hours, without fasting, and following water diuresis. Medullary and cortical apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were measured and compared in the four different states of hydration. DTI was performed with a 3T magnetic resonance imaging (MRI) system using fat-saturated single-shot spin-echo echo planar imaging sequence., Results: ADC of normal cortex (2.387 ± 0.081 × 10(-3) mm(2) /s) was significantly higher (t = 20.126, P = 0) than that of medulla (1.990 ± 0.063 × 10(-3) mm(2) /s). The FA value of normal cortex (0.282 ± 0.017) was significantly lower (t = -42.713, P = 0) than that of medulla (0.447 ± 0.022). The ADC and FA values of the left renal cortex (2.404 ± 0.082 × 10(-3) mm(2) /s, 0.282 ± 0.017) and medulla (2.002 ± 0.081 × 10(-3) mm(2) /s, 0.452 ± 0.024) were not significantly different (P > 0.05) from those of right renal cortex (2.369 ± 0.080 × 10(-3) mm(2) /s, 0.283 ± 0.018) and medulla (1.978 ± 0.039 × 10(-3) mm(2) /s, 0.443 ± 0.019). Values for ADC (×10(-3) mm(2) /s) and FA in the 12-hour fasting, 4-hour fasting, nonfasting, and water diuresis states were 2.372 ± 0.095 and 0.278 ± 0.018, 2.387 ± 0.081 and 0.282 ± 0.017, 2.416 ± 0.051 and 0.279 ± 0.023, 2.421 ± 0.068, and 0.270 ± 0.021, respectively, in cortex, 1.972 ± 0.084 and 0.438 ± 0.014, 1.990 ± 0.063 and 0.447 ± 0.022, 2.021 ± 0.081 and 0.450 ± 0.031, 2.016 ± 0.076 and 0.449 ± 0.028, respectively, in medulla. The ADC and FA values in different hydration states were not significantly different (P > 0.05)., Conclusion: DTI of normal kidneys is feasible with reproducible ADC and FA values independent of hydration states., (© 2013 Wiley Periodicals, Inc.)

Fractional anisotropy (FA) obtained by diffusion tensor imaging (DTI) can be used to image the kidneys without any contrast media. FA of the medulla has been shown to correlate with kidney function. It is expected that higher spatial resolution would improve the depiction of small structures within the kidney. However, the achievement of high spatial resolution in renal DTI remains challenging as a result of respiratory motion and susceptibility to diffusion imaging artefacts. In this study, a targeted field of view (TFOV) method was used to obtain high-resolution FA maps and colour-coded diffusion tensor orientations, together with measures of the medullary and cortical FA, in 12 healthy subjects. Subjects were scanned with two implementations (dual and single kidney) of a TFOV DTI method. DTI scans were performed during free breathing with a navigator-triggered sequence. Results showed high consistency in the greyscale FA, colour-coded FA and diffusion tensors across subjects and between dual- and single-kidney scans, which have in-plane voxel sizes of 2 × 2 mm(2) and 1.2 × 1.2 mm(2) , respectively. The ability to acquire multiple contiguous slices allowed the medulla and cortical FA to be quantified over the entire kidney volume. The mean medulla and cortical FA values were 0.38 ± 0.017 and 0.21 ± 0.019, respectively, for the dual-kidney scan, and 0.35 ± 0.032 and 0.20 ± 0.014, respectively, for the single-kidney scan. The mean FA between the medulla and cortex was significantly different (p < 0.001) for both dual- and single-kidney implementations. High-spatial-resolution DTI shows promise for improving the characterization and non-invasive assessment of kidney function., (© 2014 The Authors. NMR in Biomedicine published by John Wiley & Sons, Ltd.)

Objective: To investigate the correlativity between the changes of blood measures related to blood stasis blocking collaterals and gene expression levels of angiotensin-converting enzyme (ACE) and ACE2 of renal cortex in diabetic rats with stasis blocking collaterals syndrome, as well as the effect of stasis removing and collaterals dredging., Methods: Male Sprague-Dawley rats were divided randomly into normal control group (C group), high-carbohydrate-fat control group (H group) and streptozotocin (STZ)-injecting group. The diabeticrats were induced from rats in the STZ-injecting, group by high-carbohydrate-fat diet combined with STZ intraperitoneal injection, with sustained high-carbohydrate-fat diet fed afterwards, and were further divided into model group (M group) and Chinese medicine of stasis removing and collaterals dredging group (Z group). Rats in the Z group were fed with stasis-removing-and-collaterals-dredging herbal granule suspension intragastrically daily for 16 weeks, while drinking water of corresponding volume was administrated to the rats in other groups. At the end of the 16th week after successful establishment of models, the ultrastructures of glomeruli in different groups were detected by a transmission electron microscopy; and blood measures related to blood stasis blocking collaterals, including lipid profile and blood viscosity measures, were tested, as well as the relative gene expressions of ACE and ACE2., Results: Changes in ultrastructures of glomeruli in the M group were characterized by lack of clarity in structure and occasional thickening of glomerular basement membrane and extensive fusion in foot processes. The correlation analysis showed that there were positive correlations between lipid profile, blood viscosity, and the ACE mRNA expression levels in the M group (P < 0.05), except for cholesterol. And except for triglyceride, the blood measures were in negative correlation with the ACE2 mRNA expression levels in the M group (P < 0.05). Compared with the C and H groups, the lipid profile, plasma viscosity and blood viscosity were significantly higher (P < 0.01). All the above-mentioned measures were significantly improved in the Z group rats (P < 0.05). ACE mRNA expression was significantly higher in the M group than in the C group(P < 0.05). ACE2 mRNA level was significantly lower in the M group than in the C and H groups (P < 0.01); and its level in the Z group was higher than that in the M group (P < 0.01)., Conclusion: Blood measures related to blood stasis blocking collaterals had positive linear correlations with ACE mRNA expression and negative linear correlations with ACE2 mRNA expression in the M group. Chinese recipe of stasis removing and collaterals dredging could play a renal protecting role for diabetic rats by reducing lipid profile and blood viscosity, down-regulating ACE mRNA expression and up-regulating ACE2 mRNA expression.

Introduction: Diagnosis of renal cortical lesions by radioisotopes in nuclear medicine is one of the most common techniques and procedures can be performed by different radiotracer. However, all these materials are accurate in determining kidney function, but there are differences between them in the field. The purpose of this study was to evaluate the effectiveness of EC scans compared with DMSA scan in the detection of cortical lesions and DRF., Methods: 65 cases, which have been referred for various reasons, for DMSA scans were enrolled. Patients 1 week after DMSA scan with the previous consent of the EC being scanned. The results were compared in terms of convergence as well as sensitivity, specificity, positive and negative predictive value of EC with respect to the results of DMSA scan., Results: PPV of EC was 100%, negative predictive value of EC was 68.75%, sensitivity of EC was 90.74% and specificity of EC was 100% in the detection of cortical lesions. DMSA scan and EC convergence rates result in cortical lesions in our study was high., Discussion: We suggest EC scan as an alternative to reduce the cost of therapy and radiation, but considering the benefits of DMSA scan, it could remain the gold standard method of diagnosis.

Purpose: To evaluate age-related change in renal corticomedullary differentiation and renal cortical thickness by means of noncontrast-enhanced steady-state free precession (SSFP) magnetic resonance imaging (MRI) with spatially selective inversion recovery (IR) pulse., Materials and Methods: The Institutional Review Board of our hospital approved this retrospective study and patient informed consent was waived. This study included 48 patients without renal diseases who underwent noncontrast-enhanced SSFP MRI with spatially selective IR pulse using variable inversion times (TIs) (700-1500 msec). The signal intensity of renal cortex and medulla were measured to calculate renal corticomedullary contrast ratio. Additionally, renal cortical thickness was measured., Results: The renal corticomedullary junction was clearly depicted in all patients. The mean cortical thickness was 3.9 ± 0.83 mm. The mean corticomedullary contrast ratio was 4.7 ± 1.4. There was a negative correlation between optimal TI for the best visualization of renal corticomedullary differentiation and age (r = -0.378; P = 0.001). However, there was no significant correlation between renal corticomedullary contrast ratio and age (r = 0.187; P = 0.20). Similarly, no significant correlation was observed between renal cortical thickness and age (r = 0.054; P = 0.712)., Conclusion: In the normal kidney, noncontrast-enhanced SSFP MRI with spatially selective IR pulse can be used to assess renal corticomedullary differentiation and cortical thickness without the influence of aging, although optimal TI values for the best visualization of renal corticomedullary junction were shortened with aging., (© 2013 Wiley Periodicals, Inc.)

Mammals that live in arid and semi-arid environments in South America present physiological mechanisms that enable them to conserve water. Body water is lost through the kidneys, lungs, skin, and intestines. Regarding renal adaptation for water conservation, several indices have been used to estimate the capacity of the kidneys to produce a maximum urine concentration. Most studies were conducted at an inter-specific level, with only few performed at the intraspecific level. In this work, we compare renal function and morphology among five populations of Southern mountain cavy, Microcavia australis, present along an aridity gradient. We hypothesized that individuals from drier zones would present morphological and functional renal modifications that imply a greater capability to conserve body water. These features were studied considering the classical indices (RMT, PMT, PMA, and RMA) and three new indices that consider area measurements; the latter showed to be more adequate to reflect intraspecific differences. Our results suggest that the morphological modifications of kidneys, that is, the greater areas of renal inner medulla, would be related to the aridity gradient where populations of Southern mountain cavy occur., (© 2014 Wiley Periodicals, Inc.)

The kidney atrophies in patients with advanced chronic kidney disease (CKD) but factors influencing kidney size in normal adults are less clear. To help define this, we measured kidney volumes on contrast-enhanced computed tomographic images from 1344 potential kidney donors (aged 18-75 years). Cortical volume per body surface area progressively declined in both genders with increased age. Statistically, this was primarily dependent on the age-related decline in glomerular filtration rate (GFR). Independent predictors of increased cortical volume per body surface area were male gender, increased GFR, increased 24-h urine albumin, current smoker, and decreased high-density lipid cholesterol. Medullary volume per body surface area increased with age in men, while it increased with age in women until the age of 50 years followed by a subsequent decline. Independent predictors of increased medullary volume per body surface area were older age, male gender, increased GFR, increased 24-h urine albumin, increased serum glucose, and decreased serum uric acid. Thus, while cortical volume declines with age along the same biological pathway as the age-related decline in GFR, albuminuria and some risk factors are actually associated with increased cortical or medullary volume among relatively healthy adults. Underlying hypertrophy or atrophy of different nephron regions may explain these findings.

Although kidney size can be important in the evaluation of renal disease, it has not been carefully studied and true volume is rarely measured, and good normative data are lacking. Wang et al. measured both cortical and medullary volumes in potential transplant donors and correlate these with physiologic, morphometric, and metabolic parameters. The results reveal interesting and potentially important correlations and differential responses between the two compartments, providing a framework for future investigation.

The objective of this study was to test the feasibility and reproducibility of in vivo high-resolution mechanical imaging of the asymptomatic human kidney. Hereby nine volunteers were examined at three different physiological states of urinary bladder filling (a normal state, urinary urgency, and immediately after urinary relief). Mechanical imaging was performed of the in vivo kidney using three-dimensional multifrequency magnetic resonance elastography combined with multifrequency dual elastovisco inversion. Other than in classical elastography, where the storage and loss shear moduli are evaluated, we analyzed the magnitude |G(⁎)| and the phase angle φ of the complex shear modulus reconstructed by simultaneous inversion of full wave field data corresponding to 7 harmonic drive frequencies from 30 to 60Hz and a resolution of 2.5mm cubic voxel size. Mechanical parameter maps were derived with a spatial resolution superior to that in previous work. The group-averaged values of |G(⁎)| were 2.67±0.52kPa in the renal medulla, 1.64±0.17kPa in the cortex, and 1.17±0.21kPa in the hilus. The phase angle φ (in radians) was 0.89±0.12 in the medulla, 0.83±0.09 in the cortex, and 0.72±0.06 in the hilus. All regional differences were significant (P<0.001), while no significant variation was found in relation to different stages of bladder filling. In summary our study provides first high-resolution maps of viscoelastic parameters of the three anatomical regions of the kidney. |G(⁎)| and φ provide novel information on the viscoelastic properties of the kidney, which is potentially useful for the detection of renal lesions or fibrosis., (© 2013 Published by Elsevier Ltd.)

Objective: To evaluate the feasibility of in vivo (23)Na imaging of the corticomedullary (23)Na gradient and to measure (23)Na transverse relaxation times (T2*) in human kidneys., Methods: In this prospective, IRB-approved study, eight healthy volunteers (4 female, 4 male; mean age 29.4 ± 3.6 years) were examined on a 7-T whole-body MR system using a (23)Na-only spine-array coil. For morphological (23)Na-MRI, a 3D gradient echo (GRE) sequence with a variable echo time scheme (vTE) was used. T2* times were calculated using a multiecho 3D vTE-GRE approach. (23)Na signal-to-noise ratios (SNR) were given on a pixel-by-pixel basis for a 20-mm section from the cortex in the direction of the medulla. T2* maps were calculated by fitting the (23)Na signal decay monoexponentially on a pixel-by-pixel basis, using least squares fit., Results: Mean corticomedullary (23)Na-SNR increased from the cortex (32.2 ± 5.6) towards the medulla (85.7 ± 16.0). The SNR increase ranged interindividually from 57.2% to 66.3%. Mean (23)Na-T2* relaxation times differed statistically significantly (P < 0.001) between the cortex (17.9 ± 0.8 ms) and medulla (20.6 ± 1.0 ms)., Conclusion: The aim of this study was to evaluate the feasibility of in vivo (23)Na MRI of the corticomedullary (23)Na gradient and to measure the (23)Na T2* relaxation times of human kidneys at 7 T., Key Points: • High field MR offers new insights into renal anatomy and physiology. • (23) Na MRI of healthy human kidneys is feasible at ultra-high field. • Renal (23) Na concentration increases from the cortex in the medullary pyramid direction. • In vivo measurements of renal (23) Na-T2* times are demonstrated at 7.0 T.

The aims of this study were to determine the total volume of the horse kidney and volume fractions of its functional subcomponents (cortex, medulla, renal pelvis) using stereological methods and investigate any possible difference in the functional subcomponents of the right and left kidneys that may arise from differences in shape. The study was carried out on the kidneys of 5 horses of different breed and sex. The weight of the kidneys was measured by a digital scale, and kidney volume was calculated by Archimedes' principle. Total kidney volume and volume fractions of subcomponents of the right and left kidneys were estimated by the Cavalieri's principle. The weights of the right and left kidneys were 550 ± 25 g and 585 ± 23 g, respectively. The volumes of the right and left kidneys estimated using the Cavalieri method were 542 ± 46 ml and 581 ± 29 ml. The relative organ weight of the kidneys was calculated as 1:330. The densities of the right and left kidneys were determined to be 1.01 and 1.00, respectively. The mean volume fractions of the cortex, medulla and renal pelvis were determined as 55.6, 42.7 and 1.7 in both kidneys. No statistically significant difference existed between morphometric data pertaining to the right and left kidneys (P > 0.05). To determine precisely whether differences in shape cause any difference in the functional subcomponents of the right and left kidneys requires further investigation of differences in the number of microscopically functional unit of the kidney such as renal glomeruli and nephrons., (© 2013 Blackwell Verlag GmbH.)

The echogenicity of the renal cortex is an important parameter to consider in dogs that are suspected to have renal dysfunction. Focal increases in echogenicity have been attributed to neoplasia, infection, calcification, fibrosis, gas, and infarction. Anisotropic backscatter has been described as a source of focally increased renal cortical echogenicity in several species. The source of anisotropy appears to be the medullary rays, which are oriented perpendicular to the renal capsule. Spatial compound imaging (SCI) is an ultrasound setting that uses beam steering to acquire and average several overlapping scans of an object from different view angles, creating a compound image that is updated in real time. The impact of insonation angle and SCI on renal cortical echogenicity was evaluated ex vivo in eight kidneys from four dogs. Significant angle-dependent differences in cortical echogenicity were detected with both microconvex and linear transducers (P < 0.0001). Furthermore, the angle-dependent echogenicity differences persisted when SCI mode was used. Our finding that echogenicity was increased using a perpendicular insonation angle (90°) relative to the tubules, compared to a parallel insonation angle (0°) should assist in the interpretation of ultrasonographic images of the dog kidney., (© 2013 Veterinary Radiology & Ultrasound.)

Purpose: To assess whether noncontrast-enhanced steady-state free precession (SSFP) magnetic resonance imaging (MRI) with time-spatial labeling inversion pulse (Time-SLIP) can improve the visibility of corticomedullary differentiation of the normal kidney., Materials and Methods: A series of noncontrast-enhanced SSFP MRI with Time-SLIP were performed in 20 patients by using various inversion times (TIs); 500-1800 msec in increments of 100 msec. In-phase (IP) and opposed-phase (OP) MR images were also obtained. The signal intensity (SI) of the renal cortex and medulla was measured to calculate corticomedullary contrast ratio (SI of cortex/medulla). Additionally, the visibility of corticomedullary differentiation was visually categorized using a four-point scale., Results: In SSFP with Time-SLIP, corticomedullary contrast ratio was highest with TI of 1200 msec in eight subjects (40%), followed by 1100 msec in seven (35%) and 1000 msec in three (15%). The corticomedullary contrast ratio in SSFP with optimal Time-SLIP (4.93 ± 1.25) was significantly higher (P < 0.001) than those of IP (1.46 ± 0.12) and OP (1.43 ± 0.14). The visibility of corticomedullary differentiation was significantly better (P < 0.001) in SSFP images with Time-SLIP (averaged grade = 4.0) than in IP images (averaged grade = 2.63) and OP images (averaged grade = 2.05)., Conclusion: SSFP MRI with Time-SLIP can improve the visibility of renal corticomedullary differentiation without using contrast agents., (Copyright © 2012 Wiley Periodicals, Inc.)

In this paper, we present an automatic renal cortex segmentation approach using the implicit shape registration and novel multiple surfaces graph search. The proposed approach is based on a hierarchy system. First, the whole kidney is roughly initialized using an implicit shape registration method, with the shapes embedded in the space of Euclidean distance functions. Second, the outer and inner surfaces of renal cortex are extracted utilizing multiple surfaces graph searching, which is extended to allow for varying sampling distances and physical constraints to better separate the renal cortex and renal column. Third, a renal cortex refining procedure is applied to detect and reduce incorrect segmentation pixels around the renal pelvis, further improving the segmentation accuracy. The method was evaluated on 17 clinical computed tomography scans using the leave-one-out strategy with five metrics: Dice similarity coefficient (DSC), volumetric overlap error (OE), signed relative volume difference (SVD), average symmetric surface distance (D(avg)), and average symmetric rms surface distance (D(rms)). The experimental results of DSC, OE, SVD, D(avg) , and D(rms) were 90.50% ± 1.19%, 4.38% ± 3.93%, 2.37% ± 1.72%, 0.14 mm ± 0.09 mm , and 0.80 mm ± 0.64 mm, respectively. The results showed the feasibility, efficiency, and robustness of the proposed method.

Magnetic resonance histology (MRH) has become a valuable tool in evaluating drug-induced toxicity in preclinical models. However, its application in renal injury has been limited. This study tested the hypothesis that MRH could detect image-based biomarkers of chronic disease, inflammation, or age-related degeneration in the kidney, laying the foundation for more extensive use in evaluating drug toxicity. We examined the entire intact kidney in a spontaneous model of chronic progressive nephropathy. Kidneys from male Sprague Dawley rats were imaged at 8 weeks (n = 4) and 52 weeks (n =4) on a 9.4 T system dedicated to MR microscopy. Several potential contrast mechanisms were explored to optimize the scanning protocols. Full coverage of the entire kidney was achieved with isotropic spatial resolution at 31 microns (voxel volume = 30 pL) using a gradient recalled echo sequence. Isotropic spatial resolution of 15 microns (voxel volume < 4 pL) was achieved in a biopsy core specimen. Qualitative age-related structural changes, such as renal cortical microvasculature, tubular dilation, interstitial fibrosis, and glomerular architecture, were apparent. The nondestructive 3D images allowed measurement of quantitative differences of kidney volume, pelvis volume, main vessel volume, glomerular size, as well as thickness of the cortex, outer medulla, and inner medulla.

To better understand the tissue distribution and activity of enzymes involved in angiotensin II (Ang II) processing, we developed a novel molecular imaging method using matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry. Mouse kidney sections (12 μm) were incubated with 10-1,000 μmol/l Ang II for 5-15 min at 37°C. The formed peptides Ang III and Ang-(1-7) were identified by MALDI-TOF/TOF. A third metabolite, Ang-(1-4), was generated from further degradation of Ang-(1-7). Enzymatic processing of Ang II was dose and time dependent and absent in heat-treated kidney sections. Distinct spatial distribution patterns (pseudocolor images) were observed for the peptides. Ang III was localized in renal medulla, whereas Ang-(1-7)/Ang-(1-4) was present in cortex. Regional specific peptide formation was confirmed using microdissected cortical and medullary biopsies. In vitro studies with recombinant enzymes confirmed activity of peptidases known to generate Ang III or Ang-(1-7) from Ang II: aminopeptidase A (APA), Ang-converting enzyme 2 (ACE2), prolyl carboxypeptidase (PCP), and prolyl endopeptidase (PEP). Renal medullary Ang III generation was blocked by APA inhibitor glutamate phosphonate. The ACE2 inhibitor MLN-4760 and PCP/PEP inhibitor Z-pro-prolinal reduced cortical Ang-(1-7) formation. Our results establish the power of MALDI imaging as a highly specific and information-rich analytical technique that will further aid our understanding of the role and site of Ang II processing in cardiovascular and renal pathologies.

D-Aspartate (D-Asp) is an endogenous substance in mammals. Degradation of D-Asp is carried out only by D-aspartate oxidase (DDO). We measured DDO activity in porcine tissues, and produced an anti-porcine DDO antibody to examine the cellular localization of DDO. All the tissues examined showed DDO activities, whereas the substrate D-Asp was not detected in kidney cortex, liver, heart, and gastric mucosa. In the kidney, intensive immunohistochemical staining for DDO was found in the epithelial cells of the proximal tubules. In the liver, the epithelial cells of interlobular bile ducts, liver sinusoid-lining cells with cytoplasmic processes, and the smooth muscle cells of arterioles were strongly stained for DDO. In the heart, cardiomyocytes and the smooth muscle cells of arterioles showed DDO-immunoreactivity. In the gastric mucosa, only the chief cells were DDO-positive. These newly identified DDO-positive cells seem to actively degrade D-Asp to prevent an excess of D-Asp from exerting harmful effects on the respective functions of porcine tissues.

Unlabelled: Accurate dosimetry in (90)Y peptide receptor radionuclide therapy (PRRT) helps to optimize the injected activity, to prevent kidney or red marrow toxicity, while giving the highest absorbed dose to tumors. The aim of this study was to evaluate whether direct (90)Y bismuth germanate or lutetium yttrium orthosilicate time-of-flight PET was accurate enough to provide dosimetry estimates suitable to (90)Y PRRT., Method: To overcome the statistical uncertainty arising from the low (90)Y positron counting rate, the computation of the cortex mean-absorbed dose was divided into 4 steps: delineation of the cortex volume of interest (VOI) on the CT scan, determination of the recovery coefficient from the cortex VOI using the point-spread function of the whole imaging process, determination of the mean cortex-absorbed dose per unit cumulated activity in the cortex (S(cortex←cortex) value) from the cortex VOI using a (90)Y voxel S value kernel, and determination of the number of decays in the cortex VOI from the PET reconstruction. Our 4-step method was evaluated using an anthropomorphic abdominal phantom containing a fillable kidney phantom based on the MIRD kidney model. Vertebrae with an attenuation similar to that of bone were also modeled. Two tumors were modeled by 7-mL hollow acrylic spheres and the spleen by a plastic bag. Activities corresponded to typical tissue uptake in a first (90)Y-DOTATOC cycle of 4.4 GBq, considered as free of significant renal toxicity. Eight successive 45-min scans were acquired on both systems., Results: Both PET systems were successful in determining absorbed dose to modeled tumors but failed to provide accurate red marrow dosimetry. Renal cortex dosimetry was reproducible for both PET systems, with an accuracy of 3% for the bismuth germanate system but only 18% for the lutetium yttrium orthosilicate time-of-flight system, which was hindered by the natural radioactivity of the crystal, especially in the most attenuated area of the kidney., Conclusion: This study supports the use of direct (90)Y PET of the first PRRT cycle to assess the kidney-absorbed dose and optimize the injected activity of the following cycles.

This is the first study of partial volume effect in quantifying renal function on dynamic contrast enhanced magnetic resonance imaging. Dynamic image data were acquired for a cohort of 10 healthy volunteers. Following respiratory motion correction, each voxel location was assigned a mixing vector representing the 'overspilling' contributions of each tissue due to the convolution action of the imaging system's point spread function. This was used to recover the true intensities associated with each constituent tissue. Thus, non-renal contributions from liver, spleen and other surrounding tissues could be eliminated from the observed time-intensity curves derived from a typical renal cortical region of interest. This analysis produced a change in the early slope of the renal curve, which subsequently resulted in an enhanced glomerular filtration rate estimate. This effect was consistently observed in a Rutland-Patlak analysis of the time-intensity data: the volunteer cohort produced a partial volume effect corrected mean enhancement of 36% in relative glomerular filtration rate with a mean improvement of 7% in r(2) fitting of the Rutland-Patlak model compared to the same analysis undertaken without partial volume effect correction. This analysis strongly supports the notion that dynamic contrast enhanced magnetic resonance imaging of kidneys is substantially affected by the partial volume effect, and that this is a significant obfuscating factor in subsequent glomerular filtration rate estimation., (Copyright (c) 2009 Elsevier Ireland Ltd. All rights reserved.)

Here, we present a novel method for culturing kidneys in low volumes of medium that offers more organotypic development compared to conventional methods. Organ culture is a powerful technique for studying renal development. It recapitulates many aspects of early development very well, but the established techniques have some disadvantages: in particular, they require relatively large volumes (1-3 mls) of culture medium, which can make high-throughput screens expensive, they require porous (filter) substrates which are difficult to modify chemically, and the organs produced do not achieve good cortico-medullary zonation. Here, we present a technique of growing kidney rudiments in very low volumes of medium-around 85 microliters-using silicone chambers. In this system, kidneys grow directly on glass, grow larger than in conventional culture and develop a clear anatomical cortico-medullary zonation with extended loops of Henle.

Purpose: To demonstrate the feasibility of diffusion tensor imaging (DTI) of kidneys with respiratory triggering, and determine the optimal imaging parameters for fraction anisotropy (FA) maps., Materials and Methods: DTI of kidneys from 16 healthy volunteers was performed using a 1.5T scanner. Five different sequences with different parameters including respiration-triggered acquisition or multiple breath-holding, slice thicknesses of 3 or 5 mm, and different numbers of signal averaging and b values were compared. FA and apparent diffusion coefficients (ADCs) of the cortex and medulla were measured. Measurement error within the same and repeated examination was examined using within-individual standard deviation (Sw)., Results: FAs of the renal cortex were lower than the medulla (mean value of a sequence ranging 0.148-0.224, 0.433-0.476) and the ADCs of the cortex were higher than the medulla (2.26-2.69x10(-3) mm2/s, 1.77-2.19x10(-3) mm2/s) in all sequences (P<0.001). The renal cortex-medulla difference was the largest, with respiratory trigger- ing including a 3-mm slice thickness, three signal averages,and a b-value=0, 200, or 400 s/mm2 (P<0.001). Sw tended to be smaller in the sequence with a b-value of 400 s/mm2., Conclusion: DTI of kidneys with respiratory triggering is feasible with excellent cortex-medulla differentiation., (Copyright (c) 2009 Wiley-Liss, Inc.)

Purpose: To determine the reference site for relative apparent diffusion coefficient (rADC) and to evaluate the benefit of rADC for detecting metastatic lymph nodes in uterine cervical cancer., Materials and Methods: Two observers independently measured ADCs in the spleen, liver, renal cortex, lumbar spine, lumbar spinal cord, and gluteus maximus on diffusion-weighted images (b value, 0 and 1000 mm/sec(2)) in 50 patients. The reference site for rADC was determined using the intra- and interobserver coefficient of variation (CV) of ADC in these organs. rADC was calculated by ADC(lesion)/ADC(reference site). The benefit of rADC over ADC was validated by comparing the area under the receiver operating curve for identifying metastatic lymph nodes in uterine cervical cancer in 130 patients., Results: The renal cortex was determined to be the reference site for rADC, as its CVs (intraobserver, 5%-7%; interobserver, 5%) were less than those of the other organs (P < 0.05). The ADC and rADC of metastatic lymph nodes (n = 29, ADC, 0.7483 x 10(-3) mm(2)/sec; rADC, 0.3832) were less than those of nonmetastatic lymph nodes (n = 229, ADC, 0.9960 x 10(-3) mm(2)/sec; rADC, 0.5383) (P < 0.05). The area under the receiver operating characteristics curve for differentiating metastatic from nonmetastatic lymph nodes was greater for rADC (0.914; 95% confidence interval [CI], 0.872-0.945) than for ADC (0.872; 95% CI, 0.825-0.910) (P = 0.007)., Conclusion: The renal cortex is an appropriate reference site for rADC and rADC may improve the accuracy for diagnosing metastatic lymph nodes in uterine cervical cancer.

Understanding dynamics of NaCl reabsorption from loops of Henle, and cellular and physiological consequences, requires a clear understanding of the structural relationships of loops with other functional elements of the inner medulla (IM). Pathways taken by ascending thin limbs (ATLs) and prebend segments along the corticopapillary axis were evaluated for the outer zone of the IM of the Munich-Wistar rat. Connectivity between these segments and microdomains of interstitium adjacent to collecting ducts (CDs) and abutting ascending vasa recta (interstitial nodal spaces) was assessed by evaluating their physical contacts. For each secondary CD cluster, the number of contacts made between the total population of ATLs and interstitial nodal spaces declines as a function of depth below the outer medulla (OM)-IM boundary at near the same exponential rate that loop number declines. The proportion of each loop that makes contact with nodal spaces is inversely related to loop length. Prebend and postbend equivalent length ATL segments lie in contact with an interstitial nodal space along nearly their entire lengths. The number of contacts made by the total population of prebend or postbend segments exhibits a marked, periodic increase and decrease as a function of depth below the OM-IM boundary; this number of contacts correlates with equivalent periodic changes in prebend number. Simulations of loop distribution indicate that small discontinuities in loop distribution contribute to periodic changes in prebend number. Convergence of IM loop bends within CD clusters likely plays an essential role in NaCl compartmentalization by promoting NaCl reabsorption near interstitial regions lying adjacent to CDs and ascending vasa recta.

In this study, we assessed the renal cortical echogenicity of clinically normal adult cats by histogram analysis to obtain basic ultrasonographic data. Ultrasound images were taken under the following sets of conditions: (1) high contrast and low gain setting using a convex probe, (2) low contrast and high gain setting using a convex probe, (3) high contrast and low gain setting using a linear probe and (4) low contrast and high gain setting using a linear probe. Echogenicity of the region of interest (ROI) in the right and left renal cortices, liver and spleen was determined by histogram analysis; kidney/spleen (Kid/Sp) and kidney/liver (Kid/Liv) echogenicity ratios were calculated. Kid/Sp and Kid/Liv values varied among different ROI sites in the kidney when obtained using the convex probe, but were constant when obtained using the linear probe. Kid/Sp measured in the middle sites of the kidney showed similar values for the different settings; however, Kid/Liv differed between probes. The present findings suggest that determination of Kid/Sp using a linear probe is a feasible method for quantitative evaluation of renal cortical echogenicity in cats.

Therapeutic effect of rosiglitazone has been reported to result from an improvement of insulin sensitivity and inhibition of glucose synthesis. As the latter process occurs in both liver and kidney cortex the aim of this study was to elucidate the rosiglitazone action on glucose formation in both tissues. Primary cultured cells of both liver and kidney cortex grown in defined medium were use throughout. To identify the mechanism responsible for drug-induced changes, intracellular gluconeogenic intermediates and enzyme activities were determined. In contrast to hepatocytes, the administration of a 10 micromol/L concentration of rosiglitazone to renal tubules resulted in about a 70% decrease in the rate of gluconeogenesis, accompanied by an approximately 75% decrease in alanine utilization and a 35% increase in lactate synthesis. The effect of rosiglitazone was not abolished by GW9662, the PPAR-gamma irreversible antagonist, indicating that this action is not dependent on PPAR-gamma activation. In view of rosiglitazone-induced changes in gluconeogenic intermediates and a diminished incorporation of 14CO2 into pyruvate, it is likely that the drug causes a decline in flux through pyruvate carboxylase and (or) phosphoenolpyruvate carboxykinase. It is likely that the hypoglycemic action of rosiglitazone is PPAR-gamma independent and results mainly from its inhibitory effects on renal gluconeogenesis.

Aims: This study was performed to determine the proportion of the parenchyma and sinus structures of pig kidneys and the distance between the collecting system and the kidney surface., Methods: Forty-one pig kidneys were analyzed. Cavalieri's principle was used to obtain the volume of the cortex, medulla and sinus, as well the proportions of the arteries, veins and collecting system in the sinus., Results: The volume of the renal parenchyma varied from 129 to 488.4 cm(3). The renal cortex was 83.79% and the medulla 16.21%. The collecting system occupied the greatest part of the sinus, ranging from 34.78 to 71.91% of the renal sinus. The collecting system was closer to the dorsal than to the ventral surface in the cranial pole (p < 0.001) and the hilar zone (p < 0.01). The distance from the collecting system to the medial border was shorter than that to the lateral border in the caudal pole (p < 0.001)., Conclusion: With this new information about the variation in thickness of the pig renal parenchyma, continued studies using the pig model are needed to support the use of radiofrequency ablation and cryoablation in deep and large renal tumors with a component in the renal sinus., (Copyright 2008 S. Karger AG, Basel.)

Purpose: First, to measure renal cortical volume (Vc) using different MRI methods combined with a semiautomatic segmentation method. Second, to compare MRI measurements of Vc using the semiautomatic segmentation method with a manual segmentation method. Third, to evaluate the reproducibility of Vc measurements., Materials and Methods: A total of 22 pigs, 13 with healthy kidneys and nine with diseased kidneys, underwent MRI with two non-contrast-agent methods (MRI 100 x 900 and MRI 300 x 1100) and one contrast-agent method (MRI Gd). For each of these methods, Vc was estimated using semiautomatic (Vc(100 x 900), Vc(300 x 1100), and Vc(Gd)), as well as manual (Vc MANUAL) segmentation. Reference volumes were estimated by stereological means (Vc STEREOLOGY). MRI-derived volumes were compared with reference volumes using a two-tailed paired t-test, and variances between methods were visualized with Bland Altman plots. Reproducibilities were analyzed using covariance analysis., Results: Neither measurements of Vc 100 x 900, Vc 300 x 1100, nor Vc Gd differed markedly from Vc STEREOLOGY using semiautomatic segmentation. Vc was comparable when semiautomatic and manual segmentations were performed at the same scan. Reproducibility of MRI estimated Vc values offered intra- and interindividual differences <5%., Conclusion: Vc can in both healthy and diseased kidneys be measured accurately with MRI using both semiautomatic and manual segmentation, and measurements can be obtained with a high reproducibility. Measurements of Vc 100 x 900 may in the future become suitable in patients with chronic renal failure., ((c) 2007 Wiley-Liss, Inc.)

Purpose: To extend observations on intra-renal oxygenation with blood oxygen level-dependent (BOLD) MRI in human and rats to mouse kidneys imaged with a human whole-body scanner., Materials and Methods: Renal BOLD MRI studies were performed on a 3.0T scanner using a multiple gradient-echo (mGRE) sequence with a custom-designed 2.0-cm surface coil to acquire six T(2)*-weighted images in mice (N = 8) at an in-plane resolution of 156 x 156 mum(2). BOLD MRI data were obtained before and after administration of furosemide (10 mg/kg intravenously [i.v.])., Results: The mean weight of eight mice was 24.6 +/- 1.0 g. The baseline renal R(2)* (mean +/- standard error [SE]) was 28.6 +/- 2.1 seconds(-1) in the renal cortex (CO), 35.4 +/- 2.2 in the outer medulla (OM), and 21.2 +/- 2.1 seconds(-1) in the inner medulla (IM). The BOLD response to furosemide (DeltaR(2)*) was 4.1 +/- 1.4 in the CO, 10.1 +/- 2.1 seconds(-1) in the OM, and 3.4 +/- 0.8 seconds(-1) in the IM in mice., Conclusion: Intrarenal BOLD MR images with sufficiently high resolution can be obtained on a human whole-body scanner when combined with a small receiver coil to allow studies in mice. Both baseline R(2)* and DeltaR(2)* values following administration of furosemide were consistent with previous experience in humans and rats.

This study presents a dual-wavelength phosphorimeter developed to measure microvascular PO2 (microPO2) in different depths in tissue and demonstrates its use in rat kidney. The used phosphorescent dye is Oxyphor G2 with excitation bands at 440 and 632 nm. The broad spectral gap between the excitation bands combined with a relatively low light absorption of 632 nm light by tissue results in a marked difference in penetration depths of both excitation wavelengths. In rat kidney, we determine the catchments depth of the 440-nm excitation to be 700 microm, whereas the catchments depth of 632 nm is as much as 4 mm. Therefore, the measurements differentiate between cortex and outer medulla, respectively. In vitro, no difference in PO2 readings between both channels was found. On the rat kidney in vivo, the measured cortical microPO2 was on average 20 Torr higher than the medullary microPO2 over a wide PO2 range induced by variations in inspired oxygen fraction. Examples provided from endotoxemia and resuscitation show differences in responses of mean cortical and medullary PO2 readings as well as in the shape of the PO2 histograms. It can be concluded that oxygen-dependent quenching of phosphorescence of Oxyphor G2 allows quantitative measurement of microPO2 noninvasively in two different depths in vivo. Oxygen levels measured by this technique in the rat renal cortex and outer medulla are consistent with previously published values detected by Clark-type oxygen electrodes. Dual-wavelength phosphorimetry is excellently suited for monitoring microPO2 changes in two different anatomical layers under pathophysiological conditions with the characteristics of providing oxygen histograms from two depths and having a penetration depth of several millimeters.

Enlarged glomerular size is a feature of focal segmental glomerulosclerosis, obesity-related glomerulopathy, diabetic nephropathy, and hypertension. The distribution of glomerular volumes within different cortical zones and glomerular volume alterations with age and obesity may contribute to understanding the evolution of these diseases. We analyzed the distributions of volumes of individual glomeruli in the superficial, middle, and juxtamedullary cortex of normal human kidneys using the disector/Cavalieri method. Volumes (V(glom)) of 720 nonsclerotic glomeruli (30 per kidney, 10 per zone) were estimated in autopsy kidneys of 24 American men, 12 aged 20 to 30 yr and 12 aged 51 to 69 yr. Black and white individuals were represented equally. The range of individual V(glom) within subjects varied from two- to eight-fold. There were no significant zonal differences in V(glom) in the young or those with body surface area (BSA) < or = 2.11 m(2). In contrast, superficial glomeruli in the older age group, in those with BSA > 2.11 m(2), and in white subjects were significantly larger than juxtamedullary glomeruli. Black subjects tended toward larger V(glom) than white subjects, and this difference was significant and most marked in the juxtamedullary zone and independent of age, BSA, and glomerular number. There is a wide range in individual V(glom) in adults. BSA, race, and age independently influence V(glom) in different zones of the renal cortex. These findings might reflect processes of aging and susceptibility factors to renal disease.

The spiny mouse is relatively mature at birth. We hypothesized that like other organs, the kidney may be more developed in the spiny mouse at birth, than in other rodents. If nephrogenesis is complete before birth, the spiny mouse may provide an excellent model with which to study the effects of an altered intrauterine environment on renal development. Due to its desert adaptation, the spiny mouse may have a reduced cortex-to-medulla ratio but an equivalent total nephron number to the C57/BL mouse. Kidneys were collected from fetal and neonatal spiny mice and sectioned for gross examination of metanephric development. Kidneys were collected from adult spiny mice (10 wk of age), and glomerular number, volume, and cortex-to-medulla ratios were determined using unbiased stereology. Nephrogenesis is complete in spiny mouse kidneys before birth. Metanephrogenesis begins at approximately day 18, and by day 38 of a 40-day gestation, the nephrogenic zone is no longer present. Spiny mice have a significantly (P < 0.001) lower total nephron number compared with C57/BL mice, although the total glomerular volume is similar. The cortex-to-medulla ratio of the spiny mouse is significantly (P < 0.01) smaller. The spiny mouse is the first rodent species shown to complete nephrogenesis before birth. This makes it an attractive candidate for the study of fetal and neonatal kidney development and function. The reduced total nephron number and cortex-to-medulla ratio in the spiny mouse may contribute to its ability to highly concentrate its urine under stressful conditions (i.e., dehydration).

Purpose: To examine the benefit of using higher field strengths for BOLD MRI to detect changes in renal medullary oxygenation following pharmacological maneuvers., Materials and Methods: Renal BOLD MRI, primarily at 1.5 T, has been shown to be useful for monitoring changes in medullary oxygenation status. We performed the present studies on a 3.0 T scanner using a multiple gradient-echo (mGRE) sequence with a multicoil array to acquire 16 T2*-weighted images within a single breath-hold. Data were obtained before and after administration of furosemide (20 mg iv)., Results: The baseline renal R2* (mean +/- SE) at 3.0 T was 37.4+/-1.2 Hz in the medulla, and 21.8 +/- 1.2 Hz in the cortex. The BOLD response to furosemide (DeltaR2*) at 3.0 T was 11.8 +/- 1.1 Hz in the medulla, and 3.0 +/- 0.5 Hz in the cortex., Conclusion: Higher magnetic field strength is beneficial for renal BOLD MRI studies. The cortico-medullary contrast on the R2* map was significantly improved at 3.0 T, with no evidence of increased bulk susceptibility artifacts. Baseline R2* and DeltaR2* in the renal medulla at 3.0 T were both significantly higher compared to our previously reported data obtained at 1.5 T.

The qualitative and quantitative study of renal cortical structures was performed seven days after unilateral nephrectomy. Adult Wistar rats (10 male and 10 female) were ether-anaesthetized and the kidneys were removed by dorsolateral approach. Renal hypertrophy was determined by measurement of kidney dry mass. The samples of renal tissue were embedded in paraffin, sectioned at 6 microns and stained by azan and haematoxylineosin methods. The volume densities of renal corpuscles, the epithelium of tubules, luminal space of tubules and cortical interstitial structures were calculated using Weibel's multipurpose test system M 42. The qualitative analysis was performed to determine possible structural sex differences of cortical parenchyma during compensatory hypertrophy. There was no significant difference in volume densities of renal corpuscles and distal tubules between control and hypertrophic kidney. The volume density of the epithelium of proximal tubules and interstitial blood vessels were statistically significant increased in hypertrophic kidney compared to the values determined in control kidney. The volume density of luminal space of proximal tubules and interstitial tissues were statistically significant decreased in hypertrophy compared to control kidney. The data from present studies shows that the increase in epithelial volume of proximal tubules and interstitial blood vessels volume have the primary role in compensatory kidney enlargement after unilateral nephrectomy, while renal corpuscles do not participate significantly.

Purpose: To generate high quality diffusion-weighted images (DWI) and corresponding isotropic ADC maps of the abdomen with full organ (kidneys) coverage in a single breath-hold., Materials and Methods: DWI was performed in 12 healthy subjects with an asymmetric, spin-echo, single-shot EPI readout on a system with high performance gradients (40 mT/minute). The isotropic diffusion coefficient was measured from maps and SNR was determined for both diffusion-weighted and reference images in the liver, spleen, pancreas, and kidneys. In six patients, single-axis diffusion encoding along three orthogonal axes (12 NEX) was employed to assess anisotropic diffusion in kidneys., Results: This technique yielded images of quality and resolution which compares favorably to that of prior work. SNR ranged from 27.0 in liver to 44.1 in kidneys for the diffusion-weighted images, and from 19.6 in liver to 39.0 in kidneys in reference images. ADCs obtained in the renal medulla, renal cortex, liver, spleen, and pancreas were (2091 +/- 55) x 10(-6), (2580 +/- 53) x 10(-6), (1697 +/- 52) x 10(-6), (1047 +/- 82) x 10(-6), and (2605 +/- 168) x 10(-6) mm(2)/second, respectively (mean +/- SE). Apparent diffusion coefficient (ADC) in the renal medulla and cortex were significantly different by paired t-test (P = 4.22 x 10(-10)). Renal medulla and cortex yielded anisotropy indices (AI) of 0.129 and 0.067, respectively., Conclusions: 1) Single-shot SE EPI DWI in the abdomen with this technique provides high quality images and maps with full organ coverage in a single breath-hold; 2) ADCs obtained in the renal medulla and cortex are significantly different; and 3) diffusion within the renal medulla is moderately anisotropic., (Copyright 2003 Wiley-Liss, Inc.)

The review presents a modern view on the functional--morphological peculiarities of 12 segments of the nephron canaliculi possessing some functional, biochemical and histologic distinctions that should be taken into account to study physiology, biochemistry, morphology and pathophysiology of the kidney.

To clarify the role of the PGI(2)/PGI(2) receptor (IP) system in rabbit cortical collecting duct (RCCD), we characterized the expression of IP receptors in the rabbit kidney. We show by Northern and Western blotting that IP mRNA and protein was detectable in all three regions of the kidney. To determine how PGI(2) signals, we compared the effects of different PGI(2) analogs [iloprost (ILP), carba-prostacyclin (c-PGI(2)), and cicaprost (CCP)] in the isolated perfused RCCD. PGI(2) analogs did not increase water flow (L(p)). Although PGI(2) analogs did not reduce an established L(p) response to 8-chlorophenylthio-cAMP, they equipotently inhibited AVP-stimulated L(p) by 45%. The inhibitory effect of ILP and c-PGI(2) on AVP-stimulated L(p) is partially reversed by the protein kinase C inhibitor staurosporine and abolished by pertussis toxin; no effect was obtained with CCP. In fura 2-loaded RCCD, CCP did not alter cytosolic Ca(2+) concentration ([Ca(2+)](i)), but, in the presence of CCP, individual infusion of ILP and PGE(2) increased [Ca(2+)](i), suggesting that CCP did not cause desensitization to either ILP or PGE(2). We concluded that ILP and c-PGI(2) activate PKC and the liberation of [Ca(2+)](i) but not CCP. This suggested an important role for phosphatidylinositol hydrolysis in mediating ILP and c-PGI(2) effects but not CCP in RCCD.

Accurate knowledge of the relationship between contrast agent concentration and tissue relaxation is a critical requirement for quantitative assessment of tissue perfusion using contrast-enhanced MRI. In the present study, using a pig model, the relationship between steady-state blood concentration levels of an iron oxide nanoparticle with a hydrated diameter of 12 nm (NC100150 Injection) and changes in the transverse and longitudinal relaxation rates (1/T2* and 1/T1, respectively) in blood, muscle, and renal cortex was investigated at 1.5 T. Ex vivo measurements of 1/T2* and 1/T1 were additionally performed in whole pig blood spiked with different concentrations of the iron oxide nanoparticle. In renal cortex and muscle, 1/T2* increased linearly with contrast agent concentration with slopes of 101 +/-22 s(-1)mM(-1) and 6.5 +/-0.9 s(-1)mM(-1) (mean +/- SD), respectively. In blood, 1/T2* increased as a quadratic function of contrast agent concentration, with different quadratic terms in the ex vivo vs. the in vivo experiments. In vivo, 1/T1 in blood increased linearly with contrast agent concentration, with a slope (T1-relaxivity) of 13.9 +/- 0.9 s(-1)mM(-1). The achievable increase in 1/T1 in renal cortex and muscle was limited by the rate of water exchange between the intra- and extravascular compartments and the 1/T1-curves were well described by a two-compartment water exchange limited relaxation model., (Copyright 2002 Wiley-Liss, Inc.)

Quantitative perfusion measurements require accurate knowledge of the correlation between first-pass signal changes and the corresponding tracer concentration in tissue. In the present study, a detailed analysis of first-pass renal cortical changes in T(1) and T(*)(2) following bolus injection of the iron oxide nanoparticle NC100150 Injection was investigated in a pig model using a double-echo gradient-echo sequence. The estimated change in 1/T(*)(2) during first pass calculated from single-echo sequences was compared to the true double-echo-derived 1/T(*)(2) curves. Using a single-echo (TE = 6 ms) spoiled gradient-echo sequence, the first-pass 1/T(*)(2) response following a bolus injection of 1 mg Fe/kg of NC100150 Injection was significantly underestimated due to counteracting T(1) effects. Signal response simulations showed that the relative error in the first-pass response decreased with increasing TE and contrast agent dose. However, both the maximum TE and the maximum dose are limited by excessive cortical signal loss, and the maximum TE is further limited by high temporal resolution requirements. The problem of T(1) contamination can effectively be overcome by using a double-echo gradient-echo sequence. This yields a first-pass response that truly reflects the tissue tracer concentration, which is a critical requirement for quantitative renal perfusion assessment., (Copyright 2002 Wiley-Liss, Inc.)