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INTRODUCTION: About 1 in 11 Americans will experience a kidney stone, but underlying causes remain obscure. The objective of the present study was to separate idiopathic calcium oxalate stone formers by whether or not they showed positive evidence of forming a stone on Randall's plaque (RP). MATERIALS AND METHODS: In patients undergoing either percutaneous or ureteroscopic procedures for kidney stone removal, all stone material was extracted and analyzed using micro-CT imaging to identify those attached to RP. Twenty-four-hour urine samples were collected weeks after the stone removal procedure and patients were off of medications that would affect urine composition. The endoscopic video was analyzed for papillary pathology (RP, pitting, plugging, dilated ducts, and loss of papillary shape) by an observer blinded to the data on stone type. The percent papillary area occupied by RP and ductal plugging was quantified using image analysis software. RESULTS: Patients having even one stone on RP (N = 36) did not differ from non-RP patients (N = 37) in age, sex, BMI, or other clinical characteristics. Compared with the non-RP group, RP stone formers had more numerous, but smaller, stones, more abundant papillary RP formation, and fewer ductal plugs, both by quantitative measurement of surface area (on average, three times more plaque area, but only 41% as much plug area as in non-RP patients) and by semiquantitative visual grading. Serum and blood values did not differ between RP and non-RP stone formers by any measure. CONCLUSIONS: Growth of many small stones on plaque seems the pathogenetic scheme for the RP stone-forming phenotype, whereas the non-RP phenotype stone pathogenesis pathway is less obvious. Higher papillary plugging in non-RP patients suggests that plugs play a role in stone formation and that these patients have a greater degree of papillary damage. Underlying mechanisms that create these distinctive phenotypes are presently unknown.

The major risk factor for kidney stone disease is idiopathic hypercalciuria. Recent evidence implicates a role for defective calcium reabsorption in the renal proximal tubule. We hypothesized that claudin-2, a paracellular cation channel protein, mediates proximal tubule calcium reabsorption. We found that claudin-2–null mice have hypercalciuria due to a primary defect in renal tubule calcium transport and papillary nephrocalcinosis that resembles the intratubular plugs in kidney stone formers. Our findings suggest that a proximal tubule defect in calcium reabsorption predisposes to papillary calcification, providing support for the vas washdown hypothesis. Claudin-2–null mice were also found to have increased net intestinal calcium absorption, but reduced paracellular calcium permeability in the colon, suggesting that this was due to reduced intestinal calcium secretion. Common genetic variants in the claudin-2 gene were associated with decreased tissue expression of claudin-2 and increased risk of kidney stones in 2 large population-based studies. Finally, we describe a family in which males with a rare missense variant in claudin-2 have marked hypercalciuria and kidney stone disease. Our findings indicate that claudin-2 is a key regulator of calcium excretion and a potential target for therapies to prevent kidney stones.

Objectives: To describe the papillary pathology found in uric acid (UA) stone formers, and to investigate the mineral form of tissue deposits. Materials and Methods: We studied eight UA stone formers treated with percutaneous nephrolithotomy. Papillae were imaged intraoperatively using digital endoscopy, and cortical and papillary biopsies were taken. Biopsies were analyzed by light microscopy, micro-CT, and microinfrared spectroscopy. Results: As expected, urine pH was generally low. UA supersaturation exceeded one in all but one case, compatible with the stone material. By intraoperative imaging, the renal papillae displayed a heterogeneous mixture of plaque and plugging, ranging from normal to severe. All patients had mineral in ducts of Bellini and inner medullary collecting ducts, mainly apatite with lesser amounts of urate and/or calcium oxalate in some specimens. Papillary and cortical interstitial tissue injury was modest despite the tubule plugging. No instance was found of a stone growing attached to either plaque or plugs. Conclusions: UA stone formers resemble those with ileostomy in having rather low urine pH while forming tubule plugs that contain crystals that can only form at pH values above those of their bulk urine. This discrepancy between tissue mineral deposits and stone type suggests that local tubular pH exceeds that of the bulk urine, perhaps because of localized tubule injury. The manner in which UA stones form and the discordance between tubule crystals and stone type remain open research questions.

Chronic kidney disease (CKD) leads to musculoskeletal impairments that are impacted by muscle metabolism. We tested the hypothesis that 10-weeks of voluntary wheel running can improve skeletal muscle mitochondria activity and function in a rat model of CKD. Groups included (n = 12–14/group): (1) normal littermates (NL); (2) CKD, and; (3) CKD-10 weeks of voluntary wheel running (CKD-W). At 35-weeks old the following assays were performed in the soleus and extensor digitorum longus (EDL): targeted metabolomics, mitochondrial respiration, and protein expression. Amino acid-related compounds were reduced in CKD muscle and not restored by physical activity. Mitochondrial respiration in the CKD soleus was increased compared to NL, but not impacted by physical activity. The EDL respiration was not different between NL and CKD, but increased in CKD-wheel rats compared to CKD and NL groups. Our results demonstrate that the soleus may be more susceptible to CKD-induced changes of mitochondrial complex content and respiration, while in the EDL, these alterations were in response the physiological load induced by mild physical activity. Future studies should focus on therapies to improve mitochondrial function in both types of muscle to determine if such treatments can improve the ability to adapt to physical activity in CKD.

Kidney stones frequently develop as an overgrowth on Randall's plaque (RP) which is formed in the papillary interstitium. The organic composition of RP is distinct from stone matrix in that RP contains fibrillar collagen; RP in tissue has also been shown to have two proteins that are also found in stones, but otherwise the molecular constituents of RP are unstudied. We hypothesized that RP contains unique organic molecules that can be differentiated from the stone overgrowth by fluorescence. To test this, we used micro-CT-guided polishing to expose the interior of kidney stones for multimodal imaging with multiphoton, confocal and infrared microscopy. We detected a blue autofluorescence signature unique to RP, the specificity of which was also confirmed in papillary tissue from patients with stone disease. High-resolution mineral mapping of the stone also showed a transition from the apatite within RP to the calcium oxalate in the overgrowth, demonstrating the molecular and spatial transition from the tissue to the urine. This work provides a systematic and practical approach to uncover specific fluorescence signatures which correlate with mineral type, verifies previous observations regarding mineral overgrowth onto RP and identifies a novel autofluorescence signature of RP demonstrating RP's unique molecular composition.

Renal stones are common, with a prevalence of 5 to 10% worldwide. Acute stone passage almost always produces the severe pain of renal colic, but stones are often asymptomatic and discovered incidentally on imaging. Prevalence of both symptomatic and asymptomatic disease appears to be rising, although the relative contributions of increasing use of more sensitive imaging modalities and real changes relating to diet and lifestyle are debated. The initial evaluation of patients with renal colic optimally includes noncontrast CT to accurately visualize the size and location of stones in the urinary tract. Initial management of stones less than 5 mm in diameter in patients without anatomical abnormalities of the urinary tract is to provide adequate analgesia coupled with α-blockade, followed by watchful waiting to allow time for stone passage. The presence of urinary tract infection, inability to take oral fluids, or obstruction of a single functioning kidney requires hospitalization and active management. Once the acute episode of stone passage or removal is over, thought should be given to diagnosis of the underlying causes and steps taken towards prevention. Since stone analysis is the cornerstone of diagnosis, the patient should be encouraged to collect any stones passed and retain them for analysis. Most stones (66–76%) are formed of calcium oxalate: other types include calcium phosphate (12–17%), uric acid (7–11%), struvite (magnesium ammonium phosphate, 2–3%), and cystine (1–2%). They form because urine becomes supersaturated with respect to the solute, and treatment to lower its concentration can prevent recurrence. This chapter describes the aetiology, pathogenesis, diagnosis and treatment of calcium oxalate stones, calcium phosphate stones, uric acid stones, struvite stones, cystine stones, and nephrocalcinosis.

Introduction: There is evidence that patients with a history of ileostomies, who produce acidic urine and form uric acid or calcium oxalate stones, may plug some collecting ducts with calcium phosphate (CaP) and urate crystals. This is a paradoxical finding as such minerals should not form at an acid pH. One possible explanation is the presence of acidification defects due to focal damage to inner medullary collecting duct and Bellini duct (BD) cells. We sought to further investigate this hypothesis through direct measurement of ductal pH in dilated BDs in patients with ileostomies undergoing percutaneous nephrolithotomy (PCNL) for stone removal. Methods: After obtaining institutional review board approval, we used a fiber-optic pH microsensor with a 140-μm-diameter tip to measure intraluminal pH from the bladder, saline irrigant, and dilated BDs of patients undergoing PCNL. Results: Measurements were taken from three patients meeting inclusion criteria. Measured pH of bladder urine ranged from 4.97 to 5.58 and pH of saline irrigant used during surgery ranged from 5.17 to 5.75. BD measurements were achieved in 11 different BDs. Mean intraductal BD pH was more than 1 unit higher than bulk urine (6.43 ± 0.22 vs 5.31 ± 0.22, p

OBJECTIVE: To determine if an innovative extracorporeal electrohydraulic shock wave device (sparker array) can effectively fracture artificial stones in vitro and in vivo, and if sparker array treatment produces a renal lesion in our pig model of lithotripsy injury. Results of these experiments will be used to help evaluate the suitability of this device as a clinical lithotripter. METHODS: Utracal-30 artificial stones were placed in a holder at the focus of the sparker array and treated with 600 shock waves (21.6 kV, 60 shocks/min). Stone fragments were collected, dried and weighed to determine stone breakage. In vivo stone breakage entailed implanting stones into pigs. These stones were treated with 600 or 1200 shock waves and the fragments collected for analysis. Lesion analysis consisted of treating the left kidney of pigs with 1200 or 2400 shock waves and quantitating the hemorrhagic lesion. RESULTS: In vitro, 71±2% of each artificial stone was fractured to < 2 mm in size. In vivo stone breakage averaged 63%. Renal injury analysis revealed that only 1 out of 7 kidneys showed evidence of hemorrhagic injury in the treated area. CONCLUSIONS: The sparker array consistently comminuted artificial stones demonstrating its ability to fracture stones like other lithotripters. Also, the sparker array caused little to no renal injury at the settings used in this study. These findings suggest further research is warranted to determine the potential of this device as a clinical lithotripter.

Mechanisms of early stone retention in the kidney are under studied and poorly understood. To date attachment via Randall's plaque is the only widely accepted theory in this regard, which is best described in idiopathic calcium oxalate stone formers. Brushite stone formers are known to have distinct papillary morphology relative to calcium oxalate stone formers. As such we sought to determine whether stone attachment mechanisms in such patients may be similarly unique.Patients undergoing percutaneous and or ureteroscopic procedures for stone removal consented to endoscopic renal papillary examination and individual stone collection. Each removed stone was processed using micro computerized tomography to assess the 3-dimensional microstructure and the minerals contained, and search for common structural features indicative of novel mechanisms of early growth and attachment to renal tissue.A total of 25 intact brushite stones were removed from 8 patients and analyzed. Video confirmed attachment of 13 of the 25 stones with the remainder believed to have been accidently dislodged during the procedure. Microscopic examination by light and computerized tomography failed to show evidence of Randall's plaque associated with any stone containing brushite. Conversely each brushite stone demonstrated microstructural evidence of having grown attached to a ductal plug formed of apatite.Three-dimensional analysis of small brushite stones suggests overgrowth on ductal apatite plugs as a mechanism of early stone growth and retention. Such findings represent what is to our knowledge the initial supporting evidence for a novel mechanism of stone formation which has previously been hypothesized but never verified.

In this paper, an extracorporeal shock wave source composed of small ellipsoidal sparker units is described. The sparker units were arranged in an array designed to produce a coherent shock wave of sufficient strength to fracture kidney stones. The objective of this paper was to measure the acoustical output of this array of 18 individual sparker units and compare this array to commercial lithotripters. Representative waveforms acquired with a fiber-optic probe hydrophone at the geometric focus of the sparker array indicated that the sparker array produces a shock wave (P+ ∼40–47 MPa, P− ∼2.5–5.0 MPa) similar to shock waves produced by a Dornier HM-3 or Dornier Compact S. The sparker array's pressure field map also appeared similar to the measurements from a HM-3 and Compact S. Compared to the HM-3, the electrohydraulic technology of the sparker array produced a more consistent SW pulse (shot-to-shot positive pressure value standard deviation of ±4.7 MPa vs ±3.3 MPa).

Introduction We have previously found that papillary histopathology differs greatly between calcium oxalate and brushite stone formers (SF); the latter have much more papillary mineral deposition, tubular cell injury, and tissue fibrosis. Methods In this study, we applied unbiased orthogonal omics approaches on biopsied renal papillae and extracted stones from patients with brushite or calcium oxalate (CaOx) stones. Our goal was to discover stone type-specific molecular signatures to advance our understanding of the underlying pathogenesis. Results Brushite SF did not differ from CaOx SF with respect to metabolic risk factors for stones but did exhibit increased tubule plugging in their papillae. Brushite SF had upregulation of inflammatory pathways in papillary tissue and increased neutrophil markers in stone matrix compared with those with CaOx stones. Large-scale 3-dimensional tissue cytometry on renal papillary biopsies showed an increase in the number and density of neutrophils in the papillae of patients with brushite versus CaOx, thereby linking the observed inflammatory signatures to the neutrophils in the tissue. To explain how neutrophil proteins appear in the stone matrix, we measured neutrophil extracellular trap (NET) formation—NETosis—and found it significantly increased in the papillae of patients with brushite stones compared with CaOx stones. Conclusion We show that increased neutrophil infiltration and NETosis is an unrecognized factor that differentiates brushite and CaOx SF and may explain the markedly increased scarring and inflammation seen in the papillae of patients with brushite stones. Given the increasing prevalence of brushite stones, the role of neutrophil activation in brushite stone formation requires further study., Graphical abstract

Nephrolithiasis, or stones, is one of the oldest urological diseases, with descriptions and treatment strategies dating back to ancient times. Despite the enormous number of patients affected by stones, a surprising lack of conceptual understanding of many aspects of this disease still exists. This lack of understanding includes mechanisms of stone formation and retention, the clinical relevance of different stone compositions and that of formation patterns and associated pathological features to the overall course of the condition. Fortunately, a number of new tools are available to assist in answering such questions. New renal endoscopes enable kidney visualization in much higher definition than was previously possible, while micro-CT imaging is the optimal technique for assessment of stone microstructure and mineral composition in a nondestructive fashion. Together, these tools have the potential to provide novel insights into the aetiology of stone formation that might unlock new prevention and treatment strategies, and enable more effective management of patients with nephrolithiasis.

The most common presentation of nephrolithiasis is idiopathic calcium stones in patients without systemic disease. Most stones are primarily composed of calcium oxalate and form on a base of interstitial apatite deposits, known as Randall’s plaque. By contrast some stones are composed largely of calcium phosphate, as either hydroxyapatite or brushite (calcium monohydrogen phosphate), and are usually accompanied by deposits of calcium phosphate in the Bellini ducts. These deposits result in local tissue damage and might serve as a site of mineral overgrowth. Stone formation is driven by supersaturation of urine with calcium oxalate and brushite. The level of supersaturation is related to fluid intake as well as to the levels of urinary citrate and calcium. Risk of stone formation is increased when urine citrate excretion is 200 mg per day also increase stone risk and often result in negative calcium balance. Reduced renal calcium reabsorption has a role in idiopathic hypercalciuria. Low sodium diets and thiazide-type diuretics lower urine calcium levels and potentially reduce the risk of stone recurrence and bone diseas

Randall’s plaque, an attachment site over which calcium oxalate stones form, begins in the basement membranes of thin limbs of the loop of Henle. The mechanism of its formation is unknown. Possibly, enhanced delivery of calcium out of the proximal tubule, found in many stone formers, increases reabsorption of calcium from the thick ascending limb into the interstitium around descending vasa recta, which convey that calcium into the deep medulla, and raises supersaturations near thin limbs (“vas washdown”). According to this hypothesis, plaque should form preferentially on ascending thin limbs, which do not reabsorb water. We stained serial sections of papillary biopsies from stone-forming patients for aquaporin 1 (which is found in the descending thin limb) and the kidney-specific chloride channel ClC-Ka (which is found in the ascending thin limb). Plaque (which is detected using Yasue stain) colocalized with ClC-Ka, but not with aquaporin 1 (χ2 = 464, P < 0.001). We conclude that plaque forms preferentially in the basement membranes of ascending thin limbs, fulfilling a critical prediction of the vas washdown theory of plaque pathogenesis. The clinical implication is that treatments such as a low-sodium diet or thiazide diuretics that raise proximal tubule calcium reabsorption may reduce formation of plaque as well as calcium kidney stones.

Nephrolithiasis is a highly prevalent disorder affecting approximately one in eleven people and is associated with multiple complications including hypertension, cardiovascular disease, and chronic kidney disease. Significant epidemiologic associations with chronic kidney disease and ESRD have been noted and are reviewed herein, but debate persists in the literature as to whether kidney stone formation is a pathogenic process contributing to kidney disease. Corroborating evidence supporting the presence of kidney disease in stone formers includes the variability of renal function by stone type, the positive association of stone size with renal dysfunction, the presence of markers of renal injury in the urine of even asymptomatic stone formers, and direct evidence of renal tissue injury on histopathology. Proposed pathogenic mechanisms include recurrent obstruction and comorbid conditions such as recurrent urinary tract infections and structural abnormalities. Recent work evaluating the renal histopathology of different groups of stone formers adds further granularity, suggesting variability in mechanisms of renal injury by stone type and confirming the pathogenic effects of crystal formation. Genetic abnormalities leading to stone formation including cystinuria and primary hyperoxaluria, among others, contribute to the burden of disease in the stone-forming population.

Idiopathic hypercalciuria (IH) is a common familial trait among patients with calcium nephrolithiasis. Previously, we have demonstrated that hypercalciuria is primarily due to reduced renal proximal and distal tubule calcium reabsorption. Here, using measurements of the clearances of sodium, calcium, and endogenous lithium taken from the General Clinical Research Center, we test the hypothesis that patterns of segmental nephron tubule calcium reabsorption differ between the sexes in IH and normal subjects. When the sexes are compared, we reconfirm the reduced proximal and distal calcium reabsorption. In IH women, distal nephron calcium reabsorption is decreased compared to normal women. In IH men, proximal tubule calcium reabsorption falls significantly, with a more modest reduction in distal calcium reabsorption compared to normal men. Additionally, we demonstrate that male IH patients have lower systolic blood pressures than normal males. We conclude that women and men differ in the way they produce the hypercalciuria of IH, with females reducing distal reabsorption and males primarily reducing proximal tubule function.

Medullary sponge kidney (MSK) is associated with recurrent stone formation, but the clinical phenotype is unclear because patients with other disorders may be incorrectly labeled MSK. We studied 12 patients with histologic findings pathognomonic of MSK. All patients had an endoscopically recognizable pattern of papillary malformation, which may be segmental or diffuse. Affected papillae are enlarged and billowy, due to markedly enlarged inner medullary collecting ducts (IMCD), which contain small, mobile ductal stones. Patients had frequent dilation of Bellini ducts, with occasional mineral plugs. Stones may form over white (Randall's) plaque, but most renal pelvic stones are not attached, and have a similar morphology as ductal stones, which are a mixture of calcium oxalate and apatite. Patients had no abnormalities of urinary acidification or acid excretion; the most frequent metabolic abnormality was idiopathic hypercalciuria. Although both Runx2 and Osterix are expressed in papillae of MSK patients, no mineral deposition was seen at the sites of gene expression, arguing against a role of these genes in this process. Similar studies in idiopathic calcium stone formers showed no expression of these genes at sites of Randall's plaque. The most likely mechanism for stone formation in MSK appears to be crystallization due to urinary stasis in dilated IMCD with subsequent passage of ductal stones into the renal pelvis where they may serve as nuclei for stone formation.

Our previous work has shown that stone formers who form calcium phosphate (CaP) stones that contain any brushite (BRSF) have a distinctive renal histopathology and surgical anatomy when compared with idiopathic calcium oxalate stone formers (ICSF). Here we report on another group of idiopathic CaP stone formers, those forming stone containing primarily hydroxyapatite, in order to clarify in what ways their pathology differs from BRSF and ICSF. Eleven hydroxyapatite stone formers (HASF) (2 males, 9 females) were studied using intra-operative digital photography and biopsy of papillary and cortical regions to measure tissue changes associated with stone formation. Our main finding is that HASF and BRSF differ significantly from each other and that both differ greatly from ICSF. Both BRSF and ICSF patients have significant levels of Randall's plaque compared with HASF. Intra-tubular deposit number is greater in HASF than BRSF and nonexistent in ICSF while deposit size is smaller in HASF than BRSF. Cortical pathology is distinctly greater in BRSF than HASF. Four attached stones were observed in HASF, three in 25 BRSF and 5-10 per ICSF patient. HASF and BRSF differ clinically in that both have higher average urine pH, supersaturation of CaP, and calcium excretion than ICSF. Our work suggests that HASF and BRSF are two distinct and separate diseases and both differ greatly from ICSF.

Focused ultrasonic propulsion is a new noninvasive technique designed to move kidney stones and stone fragments out of the urinary collecting system. However, to our knowledge the extent of tissue injury associated with this technique is not known. We quantitated the amount of tissue injury produced by focused ultrasonic propulsion under simulated clinical treatment conditions and under conditions of higher power or continuous duty cycles. We compared those results to extracorporeal shock wave lithotripsy injury.A human calcium oxalate monohydrate stone and/or nickel beads were implanted by ureteroscopy in 3 kidneys of live pigs weighing 45 to 55 kg and repositioned using focused ultrasonic propulsion. Additional pig kidneys were exposed to extracorporeal shock wave lithotripsy level pulse intensity or continuous ultrasound exposure 10 minutes in duration using an ultrasound probe transcutaneously or on the kidney. These kidneys were compared to 6 treated with an unmodified Dornier HM3 lithotripter (Dornier Medical Systems, Kennesaw, Georgia) using 2,400 shocks at 120 shock waves per minute and 24 kV. Histological analysis was performed to assess the volume of hemorrhagic tissue injury created by each technique according to the percent of functional renal volume.Extracorporeal shock wave lithotripsy produced a mean ± SEM lesion of 1.56% ± 0.45% of functional renal volume. Ultrasonic propulsion produced no detectable lesion with simulated clinical treatment. A lesion of 0.46% ± 0.37% or 1.15% ± 0.49% of functional renal volume was produced when excessive treatment parameters were used with the ultrasound probe placed on the kidney.Focused ultrasonic propulsion produced no detectable morphological injury to the renal parenchyma when using clinical treatment parameters but produced injury comparable in size to that of extracorporeal shock wave lithotripsy when using excessive treatment parameters.

The sequence of events by which primary hyperoxaluria type 1 (PH1) causes renal failure is unclear. We hypothesize that proximal tubule (PT) is vulnerable because oxalate secretion raises calcium oxalate (CaOx) supersaturation (SS) there, leading to crystal formation and cellular injury. We studied cortical and papillary biopsies from two PH1 patients with preserved renal function, and seven native kidneys removed from four patients at the time of transplant, after short-term ( 2 ) or longer term ( 2 ) dialysis. In these patients, and another five PH1 patients without renal failure, we calculated oxalate secretion, and estimated PT CaOx SS. Plasma oxalate was elevated in all PH1 patients and inverse to creatinine clearance. Renal secretion of oxalate was present in all PH1 but rare in controls. PT CaOx SS was >1 in all nonpyridoxine-responsive PH1 before transplant and most marked in patients who developed end stage renal disease (ESRD). PT from PH1 with preserved renal function had birefringent crystals, confirming the presence of CaOx SS, but had no evidence of cortical inflammation or scarring by histopathology or hyaluronan staining. PH1 with short ESRD showed CaOx deposition and hyaluronan staining particularly at the corticomedullary junction in distal PT while cortical collecting ducts were spared. Longer ESRD showed widespread cortical CaOx, and in both groups papillary tissue had marked intratubular CaOx deposits and fibrosis. CaOx SS in PT causes CaOx crystal formation, and CaOx deposition in distal PT appears to be associated with ESRD. Minimizing PT CaOx SS may be important for preserving renal function in PH1.

Focused ultrasound has the potential to expel small stones or residual stone fragments from the kidney, or move obstructing stones to a nonobstructing location. We evaluated the efficacy and safety of ultrasonic propulsion in a live porcine model.Calcium oxalate monohydrate kidney stones and laboratory model stones (2 to 8 mm) were ureteroscopically implanted in the renal pelvicalyceal system of 12 kidneys in a total of 8 domestic swine. Transcutaneous ultrasonic propulsion was performed using an HDI C5-2 imaging transducer (ATL/Philips, Bothell, Washington) and the Verasonics® diagnostic ultrasound platform. Successful stone relocation was defined as stone movement from the calyx to the renal pelvis, ureteropelvic junction or proximal ureter. Efficacy and procedure time was determined. Three blinded experts evaluated histological injury to the kidney in the control, sham treatment and treatment arms.All 26 stones were observed to move during treatment and 17 (65%) were relocated successfully to the renal pelvis (3), ureteropelvic junction (2) or ureter (12). Average ± SD successful procedure time was 14 ± 8 minutes and a mean of 23 ± 16 ultrasound bursts, each about 1 second in duration, were required. There was no evidence of gross or histological injury to the renal parenchyma in kidneys exposed to 20 bursts (1 second in duration at 33-second intervals) at the same output (2,400 W/cm(2)) used to push stones.Noninvasive transcutaneous ultrasonic propulsion is a safe, effective and time efficient means to relocate calyceal stones to the renal pelvis, ureteropelvic junction or ureter. This technology holds promise as a useful adjunct to surgical management for renal calculi.

Conduct a laboratory evaluation of a novel low-pressure, broad focal zone electrohydraulic lithotripter (TRT LG-380).Mapping of the acoustic field of the LG-380, along with a Dornier HM3, a Storz Modulith SLX, and a XiXin CS2012 (XX-ES) lithotripter was performed using a fiberoptic hydrophone. A pig model was used to assess renal response to 3000 shockwaves (SW) administered by a multistep power ramping protocol at 60 SW/min, and when animals were treated at the maximum power setting at 120 SW/min. Injury to the kidney was assessed by quantitation of lesion size and routine measures of renal function.SW amplitudes for the LG-380 ranged from (P(+)/P(-)) 7/-1.8 MPa at PL-1 to 21/-4 MPa at PL-11 while focal width measured ~20 mm, wider than the HM3 (8 mm), SLX (2.6 mm), or XX-ES (18 mm). For the LG-380, there was gradual narrowing of the focal width to ~10 mm after 5000 SWs, but this had negligible effect on breakage of model stones, because stones positioned at the periphery of the focal volume (10 mm off-axis) broke nearly as well as stones at the target point. Kidney injury measured less than 0.1% FRV (functional renal volume) for pigs treated using a gradual power ramping protocol at 60 SW/min and when SWs were delivered at maximum power at 120 SW/min.The LG-380 exhibits the acoustic characteristics of a low-pressure, wide focal zone lithotripter and has the broadest focal width of any lithotripter yet reported. Although there was a gradual narrowing of focal width as the electrode aged, the efficiency of stone breakage was not affected. Because injury to the kidney was minimal when treatment followed either the recommended slow SW-rate multistep ramping protocol or when all SWs were delivered at fast SW-rate using maximum power, this appears to be a relatively safe lithotripter.

Artificial stones are used in research on the mechanisms of stone breakage in shock wave lithotripsy (SWL) and in assessing lithotripter performance. We have adopted Ultracal-30 gypsum as a model, finding it suitable for SWL studies in vitro, acute animal experiments in which stones are implanted in the kidney, and as a target to compare the in vitro performance of intracorporeal lithotripters. Here we describe the preparation of U-30 stones, their material properties, shock wave (SW) breakage characteristics, and methods used for quantitation of stone fragmentation with this model. Ultracal-30 gypsum cement was mixed 1:1 with water, cast in plastic multi-well plates, then, the stones were liberated by dissolving the plastic with chloroform and stored under water. Stone breakage in SWL was assessed by several methods including measures of the increase in projected surface area of SW-treated stones. Breakage of hydrated stones showed a linear increase in fragment area with increased SW-number and SW-voltage. Stones stored in water for an extended time showed reduced fragility. Dried stones could be rehydrated so that breakage was not different from stones that had never been dry, but stones rehydrated for less than 96 h showed increased fragility to SWs. The physical properties of U-30 stones place them in the range reported for natural stones. U-30 stones in vitro and in vivo showed equivalent response to SW-rate, with approximately 200% greater fragmentation at 30 SW/min compared to 120 SW/min, suggesting that the mechanisms of SW action are similar under both conditions. U-30 stones provide a convenient, reproducible model for SWL research.

A multi-frame high-speed photography was used to investigate the dynamics of cavitation bubbles induced by a passage of a lithotripter shock wave in a water tank. Solitary bubbles in the free field each radiated a shock wave upon collapse, and typically emitted a micro-jet on the rebound following initial collapse. For bubbles in clouds, emitted jets were directed toward neighboring bubbles and could break the spherical symmetry of the neighboring bubbles before they in turn collapsed. Bubbles at the periphery of a cluster underwent collapse before the bubbles at the center. Observations with high-speed imaging confirm previous predictions that bubbles in a cavitation cloud do not cycle independently of one another but instead interact as a dynamic bubble cluster. © 2006 American Institute of Physics.

Pretreating a pig kidney with 500 low-energy shock waves (SWs) before delivering a clinical dose of SWs (2000 SWs, 24 kV, 120 SWs/min) has been shown to significantly reduce the size of the hemorrhagic lesion produced in that treated kidney, compared with a protocol without pretreatment. However, since the time available for patient care is limited, we wanted to determine if fewer pretreatment SWs could be used in this protocol. As such, we tested if pretreating with 300 SWs can initiate the same reduction in renal lesion size as has been observed with 500 SWs.Fifteen female farm pigs were placed in an unmodified Dornier HM-3 lithotripter, where the left kidney of each animal was targeted for lithotripsy treatment. The kidneys received 300 SWs at 12 kV (120 SWs/min) followed immediately by 2000 SWs at 24 kV (120 SWs/min) focused on the lower pole. These kidneys were compared with kidneys given a clinical dose of SWs with 500 SW pretreatment, and without pretreatment. Renal function was measured both before and after SW exposure, and lesion size analysis was performed to assess the volume of hemorrhagic tissue injury (% functional renal volume, FRV) created by the 300 SW pretreatment regimen.Glomerular filtration rate fell significantly in the 300 SW pretreatment group by 1 hour after lithotripsy treatment. For most animals, low-energy pretreatment with 300 SWs significantly reduced the size of the hemorrhagic injury (to 0.8% ± 0.4%FRV) compared with the injury produced by a typical clinical dose of SWs.The results suggest that 300 pretreatment SWs in a voltage ramping treatment regimen can initiate a protective response in the majority of treated kidneys and significantly reduce tissue injury in our model of lithotripsy injury.

Intrarenal crystals trigger inflammation and renal cell necroptosis, processes that involve TNF receptor (TNFR) signaling. Here, we tested the hypothesis that TNFRs also have a direct role in tubular crystal deposition and progression of hyperoxaluria-related CKD. Immunohistochemical analysis revealed upregulated tubular expression of TNFR1 and TNFR2 in human and murine kidneys with calcium oxalate (CaOx) nephrocalcinosis-related CKD compared with controls. Western blot and mRNA expression analyses in mice yielded consistent data. When fed an oxalate-rich diet, wild-type mice developed progressive CKD, whereas Tnfr1-, Tnfr2-, and Tnfr1/2-deficient mice did not. Despite identical levels of hyperoxaluria, Tnfr1-, Tnfr2-, and Tnfr1/2-deficient mice also lacked the intrarenal CaOx deposition and tubular damage observed in wild-type mice. Inhibition of TNFR signaling prevented the induced expression of the crystal adhesion molecules, CD44 and annexin II, in tubular epithelial cells in vitro and in vivo, and treatment with the small molecule TNFR inhibitor R-7050 partially protected hyperoxaluric mice from nephrocalcinosis and CKD. We conclude that TNFR signaling is essential for CaOx crystal adhesion to the luminal membrane of renal tubules as a fundamental initiating mechanism of oxalate nephropathy. Furthermore, therapeutic blockade of TNFR might delay progressive forms of nephrocalcinosis in oxalate nephropathy, such as primary hyperoxaluria.

INTRODUCTION AND OBJECTIVES: Randall’s plaque (RP) is the origin of renal calcification on which idiopathic calcium oxalate (CaOx) kidney stones develop; however, its exact role in CaOx crystal formation remains unknown. We previously reported the potential therapeutic roles of osteopontin and macrophage (Mf) for CaOx kidney stone formation using transgenic mouse and genome-wide analysis. To establish the genomic pathogenesis of RP, we performed a microarray as well as immunohistochemical analysis for comparing the gene expressions among renal papillary RP and normal tissue of 23 CaOx, six calcium phosphate (CaP) stone formers, and normal papillary tissue of seven control patients. METHODS: We obtained the papillary tissue samples by cold cup biopsy during retrograde intrarenal surgery or ureteroscopy. Comparisons were made between: 1) RP of CaOx and CaP stone formers; 2) RP and normal tissue of CaOx stone formers and normal tissue of control patients; and 3) between RP and normal tissue of CaOx stone formers. The analyses were performed using GeneSpring13.1 and IPA software. We then validated the results using reverse transcription-polymerase chain reaction and immunohistochemistry. RESULTS: Genes that expressed more than two-fold higher levels in CaP than in CaOx stone formers included fibrinogen, collagens, P38 mitogen-activated protein kinase (MAPK), nuclear factor kB, and chemokines but decreased expressions of immune-related molecules, such as immunoglobulin, interferon-a, and T-cell receptor. Papillary tissue both from RP and normal lesions of CaOx stone-forming patients expressed activated cellular hyperpolarization, reproductive development, and molecular transport. Compared to normal papillary tissue, RP tissue contained upregulated lipocalin 2, interleukin 11, prostaglandin-endoperoxide synthase 1, glutathione peroxidase 3, and monocyte to Mf differentiation but downregulation of solute carrier family 12 member 1 and sodium leak channel non-selective (either > 2.0or 0.5-fold, p < 0.01). Network and toxicity analyses showed that these genes were associated with activated MAPK, the Akt/phosphatidylinositol 3-kinase pathway, and pro-inflammatory cytokines, which caused renal injury and oxidative stress. CONCLUSIONS: Our results are the first to establish that genes related to renal dysfunction, pro-inflammation, oxidative stress, and ion transport induce the development of RP in CaOx stone formers.

The appearance of the renal papillae in patients with nephrolithiasis can be quite variable and can range from entirely healthy to markedly diseased. The implications of such findings remain unknown. One potential reason is the lack of a standardized system to describe such features. We propose a novel grading scale to describe papillary appearance at the time of renal endoscopy.Comprehensive endoscopic renal assessment and mapping were performed on more than 300 patients with nephrolithiasis. Recurring abnormal papillary characteristics were identified and quantified based on degree of severity.Four unique papillary features were chosen for inclusion in the PPLA scoring system- ductal Plugging, Pitting, Loss of contour, and Amount of Randall's plaque. Unique scores are calculated for individual papillae based on reference examples.The description and study of renal papillary appearance in stone formers have considerable potential as both a clinical and research tool; however, a standardized grading system is necessary before using it for these purposes.

The objective of this preliminary study was to examine the spatial correlation between microbubble (MB)-induced vessel wall displacements and resultant microvascular bioeffects. MBs were injected into venules in ex vivo rat mesenteries and insonated by a single short ultrasound pulse with a center frequency of 1 MHz and peak negative pressures spanning the range of 1.5–5.6 MPa. MB and vessel dynamics were observed under ultra-high speed photomicrography. The tissue was examined by histology or transmission electron microscopy for vascular bioeffects. Image registration allowed for spatial correlation of MB-induced vessel wall motion to corresponding vascular bioeffects, if any. In cases in which damage was observed, the vessel wall had been pulled inward by more than 50% of the its initial radius. The observed damage was characterized by the separation of the endothelium from the vessel wall. Although the study is limited to a small number of observations, analytic statistical results suggest that vessel invagination comprises a principal mechanism for microvessel bioeffects in venules by microbubbles.

OBJECTIVE To test the idea that a pause (~3-min) in the delivery of shock waves (SW) soon after the initiation of treatment is unnecessary for achieving a reduction in renal injury, if treatment is begun at a low power setting that generates low-amplitude SWs. MATERIALS AND METHODS Anesthetized female pigs were assigned to one of three SWL treatment protocols that did not involve a pause in SW delivery of more than 10 seconds (2000 SWs at 24 kV; 100 SWs at 12 kV + ~10-sec pause + 2000 SWs at 24 kV; 500 SWs at 12 kV + ~10-sec pause + 2000 SWs at 24 kV; all SWs delivered at 120 SWs/min using an unmodified Dornier HM3 lithotripter). Renal function was measured before and after SWL. The kidneys were then processed for quantification of the SWL-induced hemorrhagic lesion. Values for lesion size were compared to previous data collected from pigs in which treatment included a 3-min pause in SW delivery. RESULTS All SWL treatment protocols produced a similar degree of vasoconstriction (23–41% reduction in GFR and ERPF) in the SW-treated kidney. The mean renal lesion in pigs treated with 100 low-amplitude SWs delivered before the main dose of 2000 high-amplitude SWs (2.27% FRV) was statistically similar to that measured for pigs treated with 2000 SWs all at high-amplitude (3.29% FRV). However, pigs treated with 500 low-amplitude SWs before the main SW dose had a significantly smaller lesion (0.44% FRV) that was comparable to the lesion in pigs from a previous study in which there was a 3-min pause in treatment separating a smaller initial dose of 100 low-amplitude SWs from the main dose of 2000 high-amplitude SWs (0.46% FRV). Time between the initiation of the low- and high-amplitude SWs was ~4-min for these latter two groups compared to ~1-min when there was negligible pause after the initial 100 low-amplitude SWs in the protocol. CONCLUSIONS Pig kidneys treated by SWL using a 2-step low-to-high power ramping protocol were protected from injury with negligible pause between steps, provided the time between the initiation of low-amplitude SWs and switching to high-amplitude SWs was ~4-min. Comparison with results from previous studies shows that protection can be achieved using various step-wise treatment scenarios in which either the initial dose of SWs is delivered at low-amplitude for ~4-min, or there is a definitive pause before resuming SW treatment at higher amplitude. Thus, we conclude that renal protection can be achieved without instituting a pause in SWL treatment. It remains prudent to consider that renal protection depends on the acoustic and temporal properties of SWs administered at the beginning stages of a SWL ramping protocol, and that this may differ according to the lithotripter at hand. Keywords: kidney, lithotripsy, swine, tissue injury INTRODUCTION An undesirable side effect of SWL treatment is that SWs can injure renal and surrounding tissue [1]. The primary acute lesion is vascular trauma with breakage of blood vessels and pooling of blood within the parenchyma, which if extending to the kidney surface will result in subcapsular or perirenal hematomas [1]. Along with the vascular insult, there is damage to tubules and the production and release of proinflammatory cytokines and injurious agents (e.g. iron/reactive oxygen metabolites; vasoconstrictor peptides/ischemia; metabolic toxins) that can result in fibrosis and the loss of functional tissue [1,2]. Such SW-induced injury has been linked to adverse outcomes such as hypertension, diabetes and exacerbation of kidney stone disease [3–5]. This raises concern about the long-term safety of SWL, and developing SWL treatment strategies that reduce or prevent tissue injury would certainly help mitigate such concerns. One approach to reduce SWL-induced tissue injury has been to alter the manner in which SWs are delivered to the kidney [2,6], and in this regard we have reported that treatment of the pig kidney with low-amplitude SWs followed by a 3-min pause in treatment prior to applying high-amplitude SWs will reduce SWL-induced hemorrhagic lesion sizes by as much as 20-fold [7]. In fact, similar protocols in which low-amplitude SWs were substituted with a relatively small number of higher-amplitude SWs were also shown to reduce SW-induced tissue damage, implicating the 3-min pause in treatment to be a critical factor in the development of the renal protective response [8]. On the other hand, some clinical centers begin SWL treatment at a low power setting to condition the patient to treatment-related discomfort and then gradually ramp up to higher levels with continuous delivery of SWs. That is, there is typically no pause in treatment during the lithotripsy session [9–12]. It is unclear even with power ramping if continuous delivery of SWs can be used to protect the kidney from injury. Therefore, we sought to determine in our pig model, using a 2-step ramping protocol, whether a definitive pause in SW delivery is needed in order to protect the kidney from SWL-related tissue damage.

OBJECTIVE To assess renal injury in a pig model after treatment with a clinical dose of shock waves using a narrow focal zone (≈ 3 mm) lithotriptor (Modulith SLX, Karl Storz Lithotripsy). MATERIALS AND METHODS The left kidney of anaesthetized female pigs were treated with 2000 or 4000 shock waves (SWs) at 120 SWs/min, or 2000 SWs at 60 SWs/min using the Storz SLX. Measures of renal function (glomerular filtration rate and renal plasma flow) were collected before and 1 h after shock wave lithotripsy (SWL) and the kidneys were harvested for histological analysis and morphometric quantitation of haemorrhage in the renal parenchyma with lesion size expressed as a percentage of functional renal volume (FRV). A fibre-optic probe hydrophone was used to determine acoustic output and map the focal width of the lithotriptor. Data for the SLX were compared with data from a previously published study in which pigs of the same age (7–8 weeks) were treated (2000 SWs at 120 or 60 SWs/min) using an unmodified Dornier HM3 lithotriptor. RESULTS Treatment with the SLX produced a highly focused lesion running from cortex to medulla and often spanning the full thickness of the kidney. Unlike the diffuse interstitial haemorrhage observed with the HM3, the SLX lesion bore a blood-filled core of near-complete tissue disruption devoid of histologically recognizable kidney structure. Despite the intensity of tissue destruction at the core of the lesion, measures of lesion size based on macroscopic determination of haemorrhage in the parenchyma were not significantly different from kidneys treated using the HM3 (2000 SWs, 120 SWs/min: SLX, 1.86 ± 0.52% FRV; HM3, 3.93 ± 1.29% FRV). Doubling the SW dose of the SLX from 2000 to 4000 SWs did not significantly increase lesion size. In addition, slowing the firing rate of the SLX to 60 SWs/min did not reduce the size of the lesion (2.16 ± 0.96% FRV) compared with treatment at 120 SWs/min, as was the case with the HM3 (0.42 ± 0.23% FRV vs 3.93 ± 1.29% FRV). Renal function fell significantly below baseline in all treated groups but was similar for both lithotriptors. Focal width of the SLX (≈ 2.6 mm) was about one-third that of the HM3 (≈ 8 mm) while peak pressures were higher (SLX at power level 9: P+ ≈ 90 MPa, P− ≈ −12 MPa; HM3 at 24 kV: P+ ≈ 46 MPa, P−≈−8 MPa). CONCLUSIONS The lesion produced by the SLX (narrow focal width, high acoustic pressure) was a more focused, more intense form of tissue damage than occurs with the HM3. Slowing the SW rate to 60 SWs/min, a strategy shown to be effective in reducing injury with the HM3, was not protective with the SLX. These findings suggest that the focal width and acoustic output of a lithotriptor affect the renal response to SWL. Keywords: shock wave lithotripsy, renal injury, narrow focal zone INTRODUCTION Renal injury is an unfortunate but expected consequence of shock wave lithotripsy (SWL). All patients experience at least mild haematuria, some develop subcapsular or perinephric haematomas, and in rare cases excessive bleeding can develop, requiring intervention [1–6]. SWL injury has not been well studied in patients but there is a wealth of information describing the renal response to SWs in experimental animals. The most thorough characterization has been conducted in the pig model where the severity of tissue damage and size of the haemorrhagic lesion are dependent on many factors, including treatment settings for power and shock wave (SW) rate, the sequence of SW delivery, the number of SWs and the size of the kidney [7–10]. This work in assessing treatment variables has helped to estimate the potential for injury in the clinical setting and has revealed treatment strategies that significantly reduce tissue damage [8,9,11–13]. Thus, there is a growing understanding of how treatment settings contribute to injury in SWL. However, little has been done in a systematic way to compare the injuries produced by different lithotriptors. Lithotriptors are not all the same. The SWs of all lithotriptors have similar features, but the acoustic output and dimensions of the focal zone produced by different machines can be very different [14]. Focal width is a critical feature of a lithotriptor and in working terms describes how tightly SW energy is focused in the patient. Focal width is important because it affects the mechanisms at play in stone breakage. Shear stress contributing to stone breakage is enhanced when the focal width is wider than the stone [15,16]. Also, since respiratory motion moves the stone in and out of the focal zone, a lithotriptor with larger focal width has an improved chance of hitting the target [17]. Indeed, patient studies have suggested that focal width can affect outcomes with lower stone-free rates for narrow focal width lithotriptors [18–22]. Focal width has also been implicated in SWL injury, with the suggestion of an increased occurrence of adverse effects with narrow focal width machines [23,24]. The focal widths of current lithotriptors cover a broad range, from ≈ 2.1 mm (Wolf Piezolith P3000) to ≈ 20 mm (LithoGold LG-380). Most machines are reported have a focal width of about 6–10 mm and it is not uncommon to find considerable variance for the values reported for a given machine. For example, reported values of focal width for the unmodified Dornier HM3 lithotriptor (Dornier Medical Systems, Kennesaw, GA, USA) run from ≈ 8 to ≈ 12 mm, the difference being due to how the measurements were conducted [14,25]. Accurate measures require rigorous mapping of the pressure field with a fibre-optic probe hydrophone and this is not an assessment often performed beyond the characterization required for the licensing and approval of a new lithotriptor [26]. The Storz Modulith SLX (Karl Storz Lithotripsy, Atlanta, GA, USA) is an electromagnetic lithotriptor that has gained considerable popularity within the urology community. This machine emerged during the wave of technical development spurred by interest in making SWL an anaesthesia-free procedure. Since discomfort during SWL is due largely to cutaneous sensation, the strategy used by many manufacturers was to widen the aperture of the shock source to spread the area of contact between the acoustic pulse and the body. This reduced pain at the skin but also narrowed the focal zone [14]. The SLX has a focal width of only ≈ 3 mm and produces higher acoustic pressures (P+≈ 90 MPa) than broader focal width machines (i.e. LG-380: FW ≈ 20 mm, P+≈ 20 MPa; XiXin CS2012: FW ≈ 18 mm, P+ ≈ 17 MPa; HM3: FW ≈ 8 mm, P+≈ 40 MPa) [26,27]. As kidney injury has not been adequately assessed for a narrow focal zone lithotriptor, we used the pig model to characterize the renal response to SWs for the SLX. SWs were administered under conditions that simulated clinical SWL at settings for SW number, power level and SW rate that have been reported for treating patients using this lithotriptor [28]. Data for morphology, lesion size and renal function were compared with similar, previously published data for pigs treated using the Dornier HM3 [10]. The study included assessment of the renal response to slow SW rate, a treatment strategy shown to protect against renal trauma in the pig model [9,10].

The purpose of this study was to determine if pretreatment of porcine kidneys with low-energy shock waves (SWs) prior to delivery of a clinical dose of 2,000 SWs reduces or prevents shock wave lithotripsy (SWL)-induced acute oxidative stress and inflammation in the treated kidney. Pigs (7–8 weeks old) received 2,000 SWs at 24 kV (120 SW/min) with or without pretreatment with 100 SWs at 12 kV/2 Hz to the lower pole calyx of one kidney using the HM3. Four hours post-treatment, selected samples of renal tissue were frozen for analysis of cytokine, interleukin-6 (IL-6), and stress response protein, heme oxygenase-1 (HO-1). Urine samples were taken before and after treatment for analysis of tumor necrosis factor-α (TNF-α). Treatment with 2,000 SWs with or without pretreatment caused a statistically significant elevation of HO-1 and IL-6 in the renal medulla localized to the focal zone of the lithotripter. However, the increase in HO-1 and IL-6 was significantly reduced using the pretreatment protocol compared to no pretreatment. Urinary excretion of TNF-α increased significantly (p

OBJECTIVE To determine if the magnitude of the acute injury response to shock-wave lithotripsy (SWL) depends on the number of SWs delivered to the kidney, as SWL causes acute renal oxidative stress and inflammation which are most severe in the portion of the kidney within the focal zone of the lithotripter. MATERIALS AND METHODS Pigs (7-8 weeks old) received 500, 1000 or 2000 SWs at 24 kV from a lithotripter to the lower pole calyx of one kidney. At 4 h after treatment the kidneys were removed, and samples of cortex and medulla were frozen for analysis of the cytokine, interleukin-6, and for the stress response protein, heme oxygenase-1 (HO-1). Urine samples taken before and after treatment were analysed for the inflammatory cytokine, tumour necrosis factor-α. For comparison, we included previously published cytokine data from pigs exposed to sham treatment. RESULTS Treatment with either 1000 or 2000 SWs caused a significant induction of HO-1 in the renal medulla within the focal zone of the lithotripter (F2, 1000 SWs, P < 0.05; 2000 SWs, P < 0.001). Interleukin-6 was also significantly elevated in the renal medulla of the pigs that received either 1000 or 2000 SWs (P < 0.05 and

Extensive evidence now supports the role of papillary interstitial deposits-Randall's plaques-in the formation of stones in the idiopathic, calcium oxalate stone former. These plaques begin as deposits of apatite in the basement membranes of the thin limbs of Henle's loop, but can grow to become extensive deposits beneath the epithelium covering the papillary surface. Erosion of this covering epithelium allows deposition of calcium oxalate onto this plaque material, and the transition of mineral type and organic material from plaque to stone has been investigated. The fraction of the papilla surface that is covered with Randall's plaque correlates with stone number in these patients, as well as with urine calcium excretion, and plaque coverage also correlates inversely with urine volume and pH. Two animal models--the NHERF-1 and THP-null mice--have been shown to develop sites of interstitial apatite plaque in the renal papilla. In these animal models, the sites of interstitial plaque in the inner medulla are similar to that found in human idiopathic calcium oxalate stone formers, except that the deposits in the mouse models are not localized solely to the basement membrane of the thin limbs of Henle's loop, as in humans. This may be due to the different morphology of the human versus mouse papillary region. Both mouse models appear to be important to characterize further in order to determine how well they mimic human kidney stone disease.

Nephrocalcinosis generally refers to the presence of calcium salts within renal tissue, but this term is also used radiologically in diagnostic imaging in disease states that also produce renal stones, so that it is not always clear whether it is tissue calcifications or urinary calculi that give rise to the characteristic appearance of the kidney on x-ray or computed tomography (CT). Recent advances in endoscopic imaging now allow the visual distinction between stones and papillary nephrocalcinosis, and intrarenal endoscopy can also verify the complete removal of urinary stones, so that subsequent radiographic appearance can be confidently attributed to nephrocalcinosis. This report shows exemplary cases of primary hyperparathyroidism, type I distal renal tubular acidosis, medullary sponge kidney, and common calcium oxalate stone formation. In the first three cases--all being conditions commonly associated with nephrocalcinosis--it is shown that the majority of calcifications seen by radiograph may actually be stones. In common calcium oxalate stones formers, it is shown that Randall's plaque can appear as a small calculus on CT scan, even when calyces are known to be completely clear of stones. In the current era with the use of non-contrast CT for the diagnosis of nephrolithiasis, the finding of calcifications in close association with the renal papillae is common. Distinguishing nephrolithiasis from nephrocalcinosis requires direct visual inspection of the papillae and so the diagnosis of nephrocalcinosis is essentially an endoscopic, not radiologic, diagnosis.

Data concerning nine forms of human stone disease, along with observations on normal people give new insights into formation of interstitial apatite plaque and intra-tubular crystal deposits. In general, across multiple disease states, one can reproduce the same relationships between plaque abundance as is seen among patients within individual disease states, so that the link between plaque and high urine calcium excretion, and low urine volume and pH seems increasingly secure. From this, one can propose a specific model of plaque formation, susceptible to experimental test. In many diseases, formation of inner medullary collecting duct and Bellini duct deposits is compatible with simple crystallization driven by urine supersaturations; this is expected in that these segments contain tubule fluid quite close in composition to final urine. But in ileostomy, small bowel disease and obesity bypass patients, crystals found in deposits are not those expected: apatite and urates in deposits, despite formation of highly acidic urine. Also, this discrepancy suggests the possibility of divergence between bulk urine pH and pH of focal collecting ducts, a new kind of possibility that is susceptible to experimental test.

No single theory of pathogenesis can properly account for human kidney stones, they are too various and their formation is too complex for simple understanding. Using human tissue biopsies, intraoperative imaging and such physiology data from ten different stone forming groups, we have identified at least three pathways that lead to stones. The first pathway is overgrowth on interstitial apatite plaque as seen in idiopathic calcium oxalate stone formers, as well as stone formers with primary hyperparathyroidism, ileostomy, and small bowel resection, and in brushite stone formers. In the second pathway, there are crystal deposits in renal tubules that were seen in all stone forming groups except the idiopathic calcium oxalate stone formers. The third pathway is free solution crystallization. Clear examples of this pathway are those patient groups with cystinuria or hyperoxaluria associated with bypass surgery for obesity. Although the final products may be very similar, the ways of creation are so different that in attempting to create animal and cell models of the processes one needs to be careful that the details of the human condition are included.

Study Type – Diagnostic (exploratory cohort) Level of Evidence 2b OBJECTIVE To analyse the structure and composition of unattached stones in idiopathic calcium oxalate (CaOx) stone-formers (ICSF) and compare them to attached stones from the same cohort, to investigate whether there is more than one pathogenic mechanism for stone formation in ICSF. PATIENTS AND METHODS ICSF undergoing percutaneous nephrolithotomy or ureteroscopy for the treatment of nephrolithiasis gave consent to participate in this study. All accessible renal papillae were endoscopically imaged using a digital endoscope. All stones were removed and determined by the operating surgeon to be attached or unattached to the underlying papilla. Micro-computed tomography (micro-CT), which provides three-dimensional analysis of entire stones, was used to compare the structure and composition of attached and unattached stones. RESULTS Of 115 stones collected from nine patients (12 renal units), only 25 stones were found not to be attached to renal papillae. Of these 25 stones, four were lost and 12 showed definite morphological evidence of having been attached to tissue, probably having been displaced from papillae during access. For the remaining nine stones, micro-CT analysis showed at least one internal region of calcium phosphate within each of these unattached CaOx stones, i.e. the internal structure of the unattached stones is consistent with their having originated attached to Randall’s plaque, and then having become detached but retained in the kidney, with new layers of CaOx eventually covering the original attachment site. CONCLUSIONS Micro-CT analysis supports the hypothesis that in ICSF, both attached and unattached stones occur as a result of a common pathogenic mechanism, i.e. in this type of stone former, CaOx stones, even those not showing morphology that betrays attachment, all originate attached to interstitial plaque on the renal papilla.

OBJECTIVE To present our findings of simultaneous bilateral percutaneous nephrolithotomy (sbPCNL) on bilateral renal haemodynamic and excretory function in an in vivo pig model, as despite sbPCNL being a treatment strategy for patients with bilateral renal stones, the functional response of both kidneys to such a procedure is unknown. MATERIALS AND METHODS Nine anaesthetized female pigs (≈70 kg) had a single-tract PCNL procedure in the left kidney and then the right kidney in one session (sbPCNL). Percutaneous access was achieved by a 30 F balloon dilator system. Bilateral renal function was measured before, 1.5 and 4.5 h after sbPCNL and included glomerular filtration rate (GFR), effective renal plasma flow (RPF), renal extraction of para-aminohippurate (EPAH, a measure of the efficiency of tubular organic anion transport), urine flow (UV), absolute sodium excretion (UNaV) and fractional sodium excretion (FENa). RESULTS Both kidneys had similar baseline haemodynamic and excretory function, and showed comparable changes after sbPCNL. Bilateral GFR and RPF decreased by ≈35% at 1.5 and 4.5 h after sbPCNL; EPAH was reduced to a similar degree in both kidneys at 1.5 h after sbPCNL and remained depressed throughout the observation period; bilateral UV and UNaV progressively decreased by ≈30% and ≈60% at 1.5 and 4.5 h after sbPCNL, respectively; bilateral FENa did not significantly change at 1.5 h after sbPCNL but decreased significantly by ≈50% at 4.5 h. CONCLUSIONS Both kidneys responded in a similar fashion after sbPCNL, with declines in haemodynamic and excretory function. These bilateral functional responses were comparable to those previously reported after unilateral PCNL, and help to reduce concerns that PCNL of both kidneys in one session could lead to greater functional complications, at least acutely.

The benefits of an attenuated total reflection Fourier transform infrared (ATR-FTIR) imaging approach for kidney biopsy analysis are described. Biopsy sections collected from kidney-stone formers are analyzed at the initial stages of stone development to provide insights into stone growth and formation. The majority of tissue analysis currently conducted with IR microspectroscopy is performed with a transflection method. The research presented in this manuscript demonstrates that ATR overcomes many of the disadvantages of transflection or transmission measurements for tissue analysis including an elimination of spectral artifacts. When kidney biopsies with small mineral inclusions are analyzed with a transflection approach, specular reflection and the Christiansen effect (anomalous dispersion) can occur, leading to spectral artifacts. Another effect specific to the analysis of mineral inclusions present in kidney biopsies is known as the reststrahlen effect whereby the inclusions become strong reflectors near an absorption band. ATR eliminates these effects by immersing the sample in a high index medium. Additionally, the focused beam size for ATR is decreased by a factor of four when a germanium internal reflection element is used, allowing the acquisition of spectra from small mineral inclusions several micrometers in diameter. If quantitative analysis of small mineral inclusions is ultimately desired, ATR provides the photometrically accurate spectra necessary for quantification.

Percutaneous nephrolithotomy (PCNL) can involve establishing more than one access into the urinary collecting system. The present study examined whether multiple percutaneous accesses results in a more severe reduction in renal function than that after single-percutaneous access.Adult female pigs were anesthetized, and percutaneous access to the left urinary collecting system was achieved by puncturing the lower pole calyx (single-tract access, n = 16) or serially puncturing the lower pole, interpolar region, and upper pole calyces [multiple (three)-tract access, n = 11]. Renal function measurements included glomerular filtration rate and effective renal plasma flow, and were taken immediately before and 1.5 and 4.5 hours after percutaneous access. We also examined glomerular function in a group of adult patients with normal preoperative serum creatinine (Cr) levels (or=1.4 mg/dL) who underwent either unilateral single-tract PCNL (23 patients) or unilateral multiple (two)-tract PCNL (10 patients). Access tracts were dilated to 30F with a NephroMax balloon dilator system in animal and human patients.Single- and multiple-tract percutaneous access procedures in pigs resulted in a similar renal functional response; both glomerular filtration rate and effective renal plasma flow significantly declined by approximately 60% immediately after access and remained depressed throughout the experimental observation period. A retrospective analysis of patients with normal serum Crs (or=1.4 mg/dL) who underwent single- or multiple-tract PCNL demonstrated that the procedures produced similar and significant increases in serum Cr on postoperative day 1 (0.33 +/- 0.09 [standard error of mean] mg/dL and 0.39 +/- 0.11 mg/dL, respectively) and day 2 (0.33 +/- 0.09 mg/dL and 0.25 +/- 0.09 mg/dL, respectively).Multiple-tract access does not lead to a more severe reduction in renal function than single-tract access; that is, the acute renal hemodynamic response to PCNL appears independent of the number of access tracts.