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Objective: We sought to determine if 2-h urine collection for the assessment of urine protein excretion and creatinine clearance correlates with 24-h urine collection in pregnant patients with renal disease., Methods: We enrolled patients of gestational ages ranging from 8-41 weeks, admitted as inpatients and having undergone evaluation for renal function (n = 59). We obtained the following samples: 1) 2-h urine, and 2) 24-h urine. We measured serum creatinine concentration, urinary protein, creatinine concentration, and creatinine clearance. The data was analyzed using descriptive analysis, two-way ANOVA, univariate linear regression analysis, and Bland-Altman plot comparing the efficacy of 2-h urine results with 24-h urine results., Results: We analyzed the data on 51 patients. Total proteinuria calculated by protein/creatinine (P:C) ratio in the 2-h group correlated with the total protein measured in the 24-h group (1,840.8 +/- 786 and 1,944 +/- 1,060 mg [mean +/- SE], respectively, r2 = 0.95, P < 0.0001). Creatinine clearance correlated in the 2- and 24-h groups (111 +/- 42 and 122.5 +/- 50 ml/min, respectively; r2 = 0.73, P < 0.001)., Conclusion: Two-hour urine sampling offers the same clinical information as 24-h urine collection for the evaluation of renal function. Use of 2-h urine collection reduces the time of evaluation and diagnosis, whereby increasing patient compliance and reducing errors in performance of the tests.

Variabilities exist in the relationship between serum creatinine (Se-C) and creatinine clearance (CCr) due to the influences of age, muscle mass and gender on creatinine production. We studied this variability in a group of hypertensives (n = 62, 30 male, age 44 +/- 7 years) and normotensives (n = 90, 47 male, age 42 +/- 10 years) with normal renal function (Se-C < 1.5 mg/dL). There was a wide scatter of CCr about each Se-C value. Se-C was higher in males than females and in hypertensives than normotensives, but the differences were not statistically significant. Mean Se-C for the whole group was 0.91 +/- 0.23 mg/dL and corresponded to CCr of 93 +/- 23 mL/min and 93 +/- 21 mL/min before and after adjustment to a body surface area (BSA) of 1.73 m2. Adjusted CCr was significantly lower in hypertensives than normotensives in males (86 +/- 20 mL/min Vs 99 +/- 21 mL/min, P < 0.01) and females (84 +/- 19 mL/min Vs 96 +/- 19 mL/min, P < 0.01). Crude CCr was significantly higher in men than women (P < 0.05) in the whole group but not significantly in the normotensive or hypertensive subgroups. After adjustment, the differences diminished and became insignificant in the whole group. Some subgroups had identical mean Se-C values but different adjusted CCr. A particular Se-C value did not always indicate a particular CCr. Adjustment of CCr to 1.73 m2 BSA reduced the variability between Se-C and CCr and the difference between the genders. CCr showed significant difference in renal function between subgroups where Se-C did not.

Predictability of creatinine clearance (CrCl) from serum creatinine would reduce the cost of renal care and obviate the need for 24-hours urine collection. Correlations have been established between serum creatinine (Scr) and 24-hour urinary creatinine clearance with derivation of various formulae. We have tested the applicability of these formulae in 34 Nigerian patients (22 males, 12 females) aged 18 to 58 years, (mean age 34.97 +/- 11.20 years) with established chronic renal failure (CRF) mean Scr level 742.26 +/- 388.15 mol/L. 32 age and sex matched healthy adults with serum creatinine values below 120 umol/l., served as controls. Serum creatinine and 24 hour CrCl levels were determined on two consecutive occasions. Creatinine clearance values were also derived from Scr using each of the established prediction formulae: Cockcrof and Gault [1] Gates [2] Hull et al [3]; Jelliffe [4]; and Mawer et al [5]. A relationship was sought between measured CrCl and the predicted values (derived) using the stated formulae. Regression equation were generated and correlation coefficient r, coefficient of determination r2, F-ration, prediction error, all defining the nature and strength of relationship were determined. We observed that good and statistically significant correlations exist between measured CrCl values and those predicated from the formulae (r ranging from 0.908 to 0.968 and r20.82 to 0.93 P = 0.000) and that a linear relationship exists in all cases. Cockcroft and Gault formula gave the highest coefficient of determination r2 = 0.94. It is concluded that the existing formulae are adequate for determining CrCl from Scr and should be frequently used in the long term follow-up of patients with Chronic Renal Failure (CRF) in our setting.

Lithium clearance measurements are based on the observation that lithium undergoes isoosmotic reabsorption in the proximal renal tubule to the same extent as salt and water, but undergoes neither reabsorption nor secretion elsewhere in the nephron. Consequently, lithium clearance values estimate the delivery of isoosmotic fluid to the loop of Henle and hence provide an assessment of proximal tubular reabsorption of isoosmotic fluid. If sodium clearance and urinary flow rate are also measured, then this allows the derivation of a number of parameters relating to both the absolute and relative renal handling of isoosmotic fluid in the proximal and distal regions of the kidney. Consequently, lithium clearance techniques can be used in both experimental and clinical studies to evaluate glomerulo-tubular function and provide information regarding the handling of sodium and water by the proximal and distal nephron in both health and disease. The use of lithium clearance measurements in the assessment of glomerulo-tubular function in patients treated with rIL2 for colorectal cancer is described and its application to both drug-induced toxicity and other disease states discussed.

Various carbohydrates and a variety of widely used medicines interfere with the generally used laboratory methods for determining inulin and para-aminohippuric acid (PAH). When these pitfalls are not recognized, false measurements of inulin and PAH clearances, which represent glomerular filtration rate and renal plasma flow respectively, are obtained. When performing these tests a careful history of dietary habits and oral drug therapy must be taken.

Cystatin C, a low molecular weight protein, is a new endogenous marker of renal function whose serum concentration correlates better with glomerular filtration rate than creatinine. The aim of the present study was to define a reference interval for cystatin C concentrations in children. Cystatin C was measured by an immunoturbidimetric assay in sera obtained from 258 children (93 girls, 165 boys, median age 6.29 years, range 1 day to 18 years) without evidence of kidney disease. The reference interval was calculated non-parametrically using the 2.5th and 97.5th percentiles. For comparison, creatinine was measured in the same samples. The cystatin C concentration was highest on the first days of life (range 1.64-2.59 mg/l) with a rapid decrease during the first 4 months. Beyond the 1st year, the cystatin C concentration was constant, with a reference interval of 0.7-1.38 mg/l. In contrast, serum creatinine concentrations steadily increased with age until adulthood. Compared with creatinine, cystatin C facilitates the recognition of abnormal renal function in children as its reference range is constant beyond the 1st year of life. The higher levels of cystatin C in the 1st year of life probably reflect the low glomerular filtration rate of neonates and infants.

A literature review compared the results of different kidney function tests using the inulin clearance or similar methods as a gold standard. The methodological strength of the available studies was weak. For the time being, the calculated creatinine clearance using formula, is a first choice, especially in general practice.

The need for simple and accurate methods to measure renal function is self-evident. This need increases as techniques for intervention become available. The demand for evaluation of individual kidney function has increased with its role in the diagnosis and follow-up of unilateral renal disease and in decision making for conservative or surgical treatment based on residual renal function. The role of nuclear medicine in this area has been inhibited by confusion about conflicting methodologies. This report is meant to provide guidance to those centers that would like to initiate clearance procedures but have difficulty in choosing appropriate methodology.

Seventeen kidney autopsy tissue sections from patients with cirrhosis of the liver were quantitatively examined and compared with fifteen cases of normal controls. The study was limited only to cases with normal renal function and without macroscopic renal changes. Morphometric investigations were performed by means of a computer image analysis system. The study revealed that total glomerular area, total number of glomerular cells per total glomerular area, mesangium (percentage of total glomerular area), and number of sclerotic glomeruli (percentage of total glomeruli) were significantly increased in cirrhotic patients. There was no significant increase in relative interstitial volume and in total glomerular cell per unit of glomerular area in comparison with controls. The results indicate that, despite the lack of renal clinical and laboratory manifestation, cirrhosis of the liver can be accompanied by a variety of glomerular disorders. These abnormalities consist of an enlargement of the glomeruli, an increase in glomerular cellularity proportional to the increase in glomerular size, thickening in mesangial matrix, and increased glomerulo-sclerotic lesions.

To assess the utility and precision of GFR measurements in multicenter trials, the test performance and variability of GFR were analyzed in 2,250 patients enrolled in 44 clinical centers participating in either the Modification of Diet in Renal Disease (MDRD) Study or the Diabetes Control and Complications Trial (DCCT). GRF was measured as the renal clearance of [125I]iothalamate after an sc injection without epinephrine. The studies used similar protocols for obtaining blood and urine, training clinical center staff, and processing specimens in central laboratories. The performance of GFR measurements, assessed from adherence to protocol and quality control analyses, was excellent. The variability among the four clearance periods (intratest coefficient of variation [CV]) was acceptable; the median intratest CV for GFR was 9.4% in the MDRD Study and 11.7% in the DCCT. The pattern of decline in serum counts was better approximated by an exponential rather than a linear relationship. The cause of the intratest variability in GFR measurements was explored by univariate and multivariate analysis. The intratest CV was highest at the extremes of GFR. Among patients with a high GFR (> 90 mL/min per 1.73 m2), most of whom were participants in the DCCT, the higher intratest GFR was due, in part, to a systematic decline in GFR during the test. Among patients with a very low GFR (< 13 mL/min per 1.73 m2), technical difficulties in urine collections contributed substantially to the higher intratest CV. Other patient characteristics, including age, gender, weight, serum glucose, renal diagnosis, and use of diuretics, were not strongly correlated with the intratest CV. The precision of GFR measurements was assessed from the variability from measurement to measurement (interest CV). Among MDRD Study subjects, in whom two measurements of GFR were performed over a 3-month interval, the median interest CV was relatively low (6.3%) and was only weakly related to the intratest CV. Thus, GFR measurements are reasonably precise, even if the intratest CV is high. Given the relatively high intratest CV that is characteristic of GFR measurements, the estimate of GFR in an individual is more precise if multiple clearance periods, rather than a single period, are included. Similarly, the estimate of mean GFR for a population is also more precise if multiple clearance periods are included. In conclusion, by the use of standardized methods, an acceptable precision of GFR results can be obtained in multicenter trials. The same methods can be applied in clinical practice.(ABSTRACT TRUNCATED AT 400 WORDS)

Laboratory tests that are frequently ordered in a primary care practice include complete blood count, arterial blood gases, erythrocyte sedimentation rate, creatinine clearance, and glucose tolerance. Yet, the impact of age-associated physiologic changes on interpretation of laboratory data has only recently been elucidated. With advancing age, many laboratory parameters increase or decrease, some remain unchanged, and the effect of age on still others remains unclear. Interpreting lab data in the elderly is further confounded by the multiple disease states, polypharmacy, and atypical disease presentations commonly found in this population. Additional clinical research is needed to better establish reference laboratory values in elderly patients.

Renal function can now be evaluated in utero and after birth. Most of the methods used to investigate suspected renal dysfunction or disease are not presently applicable to the fetus; however, prenatal and postnatal evaluation of renal function has assumed a greater importance as the consequences of birth before term become more apparent.

The phenolsulphthalein 60/60 plasma test (PSP 60/60) was evaluated in 30 control subjects (mean value 51 micrograms/100 ml +/- 49 micrograms/100 ml) and 60 patients with chronic renal disease with varying degrees of renal insufficiency. PSP 60/60 proved to be superior to determination of serum creatinine and urea nitrogen. PSP 60/60 correlated well with endogenous creatinine clearance and 131I-iodohippurate clearance in over 80% of cases. Of various exogenous and endogenous factors interfering with the test, drugs influencing renal excretory mechanisms are most important. Due to its technical simplicity, PSP 60/60 is a useful screening test for evaluation of renal function, especially as an office procedure.

During the four-year period from January 1980 to April 1984, 56 patients were admitted to the Pediatric Intensive Care Unit (PICU) whose care required timed urine collections using indwelling urinary catheters. The glomerular filtration rate derived from the clearance of endogenous creatinine with accurate timed urine volume is compared to that derived from the formula, 0.55 body length (cm)/plasma creatinine (mg/dl). There is a significant difference in the results between the two methods, p less than 0.0001. The largest divergence arises in those with creatinine clearance of less than 40 ml/min per 1.73 sq.m. In this subgroup, the formula derived glomerular filtration rates consistently overestimate the renal function and create a misleading assurance of minimal renal impairment. Therefore, our findings suggest that the latter formula is not applicable to PICU patients for consideration of fluid and electrolyte balance, administration of nephrotoxic drugs or criteria for dialysis.

A technique is described for rapid and reproducible analysis of split-drop micropuncture sequences recorded on film. Automatic identification of the droplet menisci in each cine frame, and subsequent evaluation is performed by a computerised T.V. image analysis system. In comparison with a more conventional technique, the improvement in reproducibility of the analysis is achieved without loss of accuracy and is accompanied by a three fold increase in speed.

Recommendations of the Study Group "Renal Function Diagnostics" of the Society of Nephrology to the performance of the steady state clearance using inulin or PAH and the slope clearance with radionuclides for estimation of effective renal plasma flow are presented. These investigations are indicated in the early recognition and follow-up of latent or residual disturbance of the renal function in the creatinine-blind area. Recommendations have been done on selection and dosage of test substances, timing of examination and evaluation of results.

Body surface area is used to standardize renal function measurements in children. This is appropriate when relating renal function to kidney size. However, standardizing renal function by lean body mass could yield additional insights into the relationships of renal function, diet, growth and general metabolism that are not apparent using surface area.

The renal clearance of unconjugated oestriol, oestriol glucosiduronate and oestriol sulphate by the kidney in late human pregnancy has been compared with simultaneous measurements of inulin clearance. The results for the fractions not bound to protein indicate that after glomerular filtration, unconjugated oestriol is completely reabsorbed, oestriol glucosiduronate is both filtered and excreted actively by the tubules, and that oestriol sulphate is filtered but not excreted or absorbed by the tubules; the administration of probenecid confirms these observations on tubular handling. The possibility of using endogenous oestril sulphate as a means of measuring the glomerular filtration rate in pregnancy is suggested.

Various in vitro methods employing radioactive indicators have been presented for the determination of glomerular filtration rate (GFR) including slope/intercept (S/I) and single sample (SS) methods. The S/I technique utilizes the analysis of the slope of a certain segment of the plasma disappearance curve of a suitable radioactive indicator and its intercept on the y axis. The SS method is based on the theoretical volumes of distribution derived from a single plasma concentration at some specific time after intravenous injection of the indicator. Using GFRs estimated from the compartmental analysis of the entire plasma disappearance curve as a reference standard, we have compared the errors of GFR estimation calculated from 12 S/I methods, 3 SS methods and 2 techniques in which original formulae were derived. The errors of the SS method of Tauxe et al. gave the lowest standard error of estimate (Sy X x) of all the methods. The S/I methods gave lowest errors when sampling times were taken between 60 min and 240 min. Almost all the errors observed here were significantly less than those observed using scintillation camera techniques. The SS method seems to be the method of choice for estimation of GFR by single injection techniques. The use of the scintillation camera in conjunction with the SS technique would provide a useful right to left ratio so that individual kidney GFR could be calculated.

THREE GROUPS OF PATIENTS: A with normal glomerular filtration rate, B with moderate and C with advanced renal damage, were dehydrated and fasted for 30 hours. At regular intervals measurements were taken of urine osmolality, urine specific gravity and serum osmolality. The time required to reach maximum urine osmolality varies with the degree of dehydration and inversely with the severity of kidney damage. In patients with normal glomerular filtration rate, maximum urine osmolality is not attained by 30 hours of dehydration. Thus, for shorter periods, all "normal ranges" of concentrating capacity must be related to specific durations of dehydration. Carefully measured urine specific gravities parallel urine osmolalities closely, especially when proteinuria and glucosuria are absent. The measurement of U/P osmolality ratio offers no clinical advantage in the assessment of renal concentration capacity over the measurement of urine osmolality alone. In Group A, hypertensives achieved higher urine concentrations than did the nonhypertensives under identical test conditions. A normal range for renal concentrating capacity has been presented.