Measurement of glomerular filtration rate by the 99mTc-DTPA renogram is less precise than measured and predicted creatinine clearance

The work was devised to compare measurements of glomerular filtration rate (GFR) by technetium-99m-diethylenetriaminepentacetic acid (99mTc-DTPA) renogram to those by creatinine clearance (measured and predicted by Cockroft and Gault) and by inulin clearance. A total number of 65 individuals were enrolled: 15 healthy controls and 50 patients with renal disease. Compared to inulin clearance used as the gold standard, 99mTc-DTPA overestimated at low and underestimated at high GFRs. 99mTc-DTPA measurements were less precise than creatinine clearance except for individuals with GFR >100 ml/min x 1.73 m2. Measured creatinine clearance had the highest correlation coefficient with inulin clearance, 99mTc-DTPA clearance the lowest. In correlation analyses, 81.5% of the interindividual variability for measured creatinine clearance could be explained by true differences in inulin clearance; this value dropped to 59.1 and 57.4% for predicted creatinine clearance and 99mTc-DTPA, respectively. In patients with GFR <25 ml/min x 1.73 m2, all 99mTc-DTPA measurements were out of the 95% confidence interval for the inulin measurement. It can be inferred that 99mTc-DTPA clearance from the renogram is less precise than measured and predicted creatinine clearance.     

Comparison of 51Cr-EDTA with 99m-Tc-DTPA slope clearance for estimation of glomerular filtration rate using the one compartment model

AIM: Of this study is to determine the relationship between 51Cr-EDTA and 99mTc-DTPA slope clearance applying the "one-compartment model". METHODS: The "one-compartment model" was chosen to calculate and to compare the glomerular filtration rates of 25 patients with normal and pathological creatinin values after injection of 51Cr-EDTA and 99mTc-DTPA simultaneously. RESULTS: The two clearance values correlated well (r = 0.996), and the 99mTc-DTPA clearance was systematically higher (28%). The 99mTc-DTPA was calculated and compared after taking three plasma samples. Taking two samples, only minor differences were seen and the correlation was high (r = 0.992). CONCLUSION: The results of this study encouraged us to adopt the use of 99mTc-DTPA instead of 51Cr-EDTA in determining the glomerular filtration applying the "one-compartment model" in slope with two plasma samples.     

Chromium-51-EDTA clearance in adults with a single-plasma sample

In 1996, a committee on renal clearance recommended a mean sojourn time-based methodology for single-sample determination of plasma clearance of 99mTc-diethylenetriamine pentaacetic acid (DTPA) to be used on adults if the patient's glomerular filtration rate (GFR) is suspected to be >30 ml/min. The main purpose of this study was to derive a mean sojourn time-based formula for calculation of 51Cr-ethylenediamine tetraacetic acid (EDTA) clearance in adults. METHODS: Two groups of patients with 51Cr-EDTA clearance (Cl) between 16 and 172 ml/min were studied. In Group I (n = 46), reference Cl was determined as a multiplasma sample, single-injection method (ClSM). Sixteen blood samples were drawn from 0 until 5 hr after a single intravenous injection of 51Cr-EDTA. In Group II (n = 1046), reference Cl was determined by the Br?chner-Mortensen four-sample clearance method (ClBM). The plasma time-activity curves of Group I were used to derive two mean sojourn time-based formulas (Formulas 1 and 2) for calculation of a single-sample clearance. Formula 1 was derived from the entire time-activity curve, whereas the derivation of Formula 2 used only the final slope of the time-activity curve. The accuracy of the two formulas and the Christensen and Groth 99mTc-DTPA formula was tested on Group II. RESULTS: Chromium-51-EDTA Cl calculated by Formula 1 was almost identical to the Cl calculated by the reference Cl method (r = 0.982; SDdiff = 5.82 ml/min). Both 51Cr-EDTA Cl calculated by Formula 2 and by the 99mTc-DTPA formula showed close correlation with the reference method (r = 0.976, r = 0.985, respectively) but systematically overestimated GFR for the whole range of clearance values by 3.5 and 3.2 ml/min (p<0.001), respectively. CONCLUSION: It is possible to get an accurate determination of 51Cr-EDTA Cl from a single-plasma sample in adults by the mean sojourn time methodology. The determination is marginally more accurate (p<0.001) if using a formula derived from the entire plasma time-activity curve than from only the final slope. The single-sample formula derived for determination of 99mTc-DTPA Cl tends slightly to overestimate GFR if used to calculate 51Cr-EDTA Cl.     

Evaluation of glomerular filtration rate by camera-based method in both children and adults

We describe a method to evaluate glomerular filtration rate (GFR) in both children and adults using 99mTc-diethylenetriamine pentaacetic acid (DTPA) and a gamma camera. METHODS: Renal scintigraphy with 99mTc-DTPA was performed in 40 children and 92 adults with various degrees of renal function. The percent renal uptake at 2-2.5 min after tracer arrival in the kidney was determined with background subtraction and correction for soft-tissue attenuation and was correlated by linear regression analysis with GFR measured from two blood samples. A perirenal region of interest was used for background subtraction. Renal depth was computed using the equations determined or validated on the basis of CT measurements, and the attenuation coefficient was set at 0.12. The obtained regression equation was used to predict GFR. Renal function was also assessed by the Gates' method. RESULTS: Percent renal uptake was closely correlated with GFR normalized for body surface area in all patients (y = 15.958x - 2.94; r = 0.939). GFR was successfully predicted using the regression equation in both children and adults. Gates' method severely overestimated GFR in children and provided less accurate values even in adults than our method. CONCLUSION: The method presented here requires neither blood sampling nor additional imaging and allows estimation of GFR in both children and adults.     

Diagnosis of thoracic outlet syndrome in the emergency department

Gadodiamide at a dose of 0.1 mmol/kg was administered intravenously to 10 renal transplanted patients with stable, impaired, or slowly deteriorating renal function (serum creatinine 194-362 mumol/l). The patients were referred for contrast medium enhanced magnetic resonance imaging to rule out possible graft circulation abnormalities. The excretion of gadodiamide in urine was prolonged as compared with healthy controls. After 120 h 92% of the injected dose was excreted in urine and only 0.4% in faeces. The plasma clearance of gadodiamide was 28.6 +/- (SD) 5.5 ml/min (n = 10), and the renal clearance (0-72 h) was 26.3 ml/min. The renal clearance of 125I-iothalamate for the same time period was 27.9 +/- 5.3 ml/min. Thus, gadodiamide is eliminated by glomerular filtration also in renal transplant patients with moderately to severe impaired renal function, and gadodiamide clearance may serve as an alternative marker for the determination of the glomerular filtration rate. Serum values of creatinine and beta(2)-microglobulin and creatinine clearance were unchanged by gadodiamide and neither was the urinary enzyme excretion significantly changed. These results suggest that the renal tolerance to gadodiamide is good also in renal transplant patients with impaired renal function.     

Renogram deconvolution in the management of diabetic nephropathy: utility of the measurement of initial tracer uptake

Our objective was to assess mean transit time (MTT) and initial uptake, both parameters derived from the renal retention function (RRF), in the study of renal function in patients with diabetic nephropathy. We studied 25 patients, 7 with type I diabetes mellitus and 18 with type II diabetes mellitus, all of whom fulfilled the criteria for diabetic nephropathy with proteinuria and/or retinopathy. We found a statistically significant correlation between initial uptake and the other biochemical and renographic parameters studied except proteinuria: serum creatinine (r = 0.66, P < 0.002), creatinine clearance (r = 0.61, P < 0.003), glomerular filtration rate (r = 0.74, P < 0.003) and effective renal plasma flow (r = 0.66, P < 0.003). The other renographic parameters studied (maximal activity of the conventional renogram and MTT of the deconvoluted renogram) did not show any correlation. Initial uptake is a semi-quantitative renographic parameter that can provide complementary information to biochemical data and it may be useful in the management of diabetic nephropathy, especially in patients with high serum creatinine or creatinine clearance.     

Chemotherapy of malignant melanoma

Previous studies have shown the kidney to be an important site for the catabolism of secretin. We have investigated possible sites within the kidney for secretin uptake in four intact anesthetized dogs. The disappearance half-time of an intravenous infusion of secretin, measured by a sensitive and specific ratioimmunoassay in four intact anesthetized dogs was 2.84 minutes. After ureteral ligation (to arrest glomerular filtration), the half-time of a similar intravenous dose of secretin was 2.78 minutes. Finally, the renal vascular pedicles were ligated to totally exclude the kidneys from the circulation and the half-time was found to be 5.43 minutes. These findings demonstrate that the efficient renal mechanisms for secretin degradation are not dependent upon glomerular filtration but upon some other mechanism, presumably located in renal tubular cells.     

Renal clearance of digoxin in premature neonates

The renal clearances of digoxin and creatinine were determined in seven premature neonates (mean gestational age = 29.9 wk, range = 26 to 36 wk) at a postnatal age of 1 to 9 days (mean = 4.1 days). The corrected renal digoxin clearance (mean, 10.4 ml/min/1.73 m2; range, 2.5 to 36.7) was highly dependent on gestational age and body weight, r being 0.95 and 0.96, respectively (exponential curve). The linear slope of corrected renal digoxin clearance vs. creatinine clearance plot approached unity (r = 0.99), indicating that digoxin and creatinine were handled similarly by the kidney in these premature neonates (i.e. glomerular filtration with some degree of tubular secretion). Our finding of slower renal digoxin clearance helps to explain the higher serum levels and longer half-life of this drug in premature neonates.     

Duplex (thermotroph-psychrotroph) quadrant plates: convenient, error-avoiding tools for monitoring of HACCP-contained food lines and for epidemiological investigations under conditions of military or other constraints

The present study evaluated whether chronically administered low-dose (<5 mg/kg) ciclosporin A (CsA) affects renal haemodynamics and tubular function in renal transplant recipients (RTx) when studied at nadir CsA blood levels. The renal clearance of lithium was used as an index of proximal tubular outflow of sodium and water. Effective renal plasma flow, glomerular filtration rate, and renal clearance of lithium were studied in 67 stable non-diabetic RTx and 44 healthy controls. Forty-eight of the RTx were treated with CsA, prednisone, and azathioprine. Nineteen were treated exclusively with prednisone and azathioprine. In RTx with a good graft function (serum-creatinine <125 micromol/l), no specific CsA-induced renal haemodynamic and tubular dysfunctions were evident. In CsA-treated RTx with a slightly reduced renal function (serum creatinine 125-180 micromol/l) a decrease in fractional proximal tubular reabsorption was found. The renal clearances of urate and magnesium were comparable between RTx treated with or without CsA, and a significant correlation between glomerular filtration rate and renal clearance of urate was found. CsA-treated RTx had a significantly higher blood pressure, independent of glomerular filtration rate and segmental tubular function. In conclusion, at nadir CsA blood levels, no specific CsA-induced tubular dysfunction evaluated by the renal lithium clearance method could be demonstrated in RTx receiving chronically low-dose CsA. The hyperuricaemia commonly seen in RTx seems to be mainly caused by the reduced glomerular filtration rate.     

Knee extensor fatigability and strength after bicycle ergometer training

Detection of early renal dysfunction remains a difficult problem because creatinine levels often do not become abnormal until glomerular filtration rate is severely reduced. Creatol, which also accumulates in renal failure, has been suggested as an alternative to creatinine. To measure glomerular filtration rate, a number of simplified techniques have been suggested; for the most part, however, they have not been validated in patients with severe chronic renal failure. Glomerular filtration rate can be estimated with fair precision from serum creatinine concentration with the use of improved equations, provided that the serum creatinine level is greater than 2 mg/dL. The use of cimetidine to reduce the discrepancy between creatinine clearance and glomerular filtration rate does not seem justifiable. In diabetic nephropathy, sequential biopsies may be preferable to sequential determinations of glomerular filtration rate for follow-up of patients with this disease.     

Cross sectional longitudinal study of spot morning urine protein:creatinine ratio, 24 hour urine protein excretion rate, glomerular filtration rate, and end stage renal failure in chronic renal disease in patients without diabetes

OBJECTIVE: To evaluate whether the protein:creatinine ratio in spot morning urine samples is a reliable indicator of 24 hour urinary protein excretion and predicts the rate of decline of glomerular filtration rate and progression to end stage renal failure in non-diabetic patients with chronic nephropathy. DESIGN: Cross sectional correlation between the ratio and urinary protein excretion rate. Univariate and multivariate analysis of baseline predictors, including the ratio and 24 hour urinary protein, of decline in glomerular filtration rate and end stage renal failure in the long term. SETTING: Research centre in Italy. SUBJECTS: 177 non-diabetic outpatients with chronic renal disease screened for participation in the ramipril efficacy in nephropathy study. MAIN OUTCOME MEASURES: Rate of decline in filtration rate evaluated by repeated measurements of unlabelled iohexol plasma clearance and rate of progression to renal failure. RESULTS: Protein:creatinine ratio was significantly correlated with absolute and log transformed 24 hour urinary protein values (P = 0.0001 and P < 0.0001, respectively.) Ratios also had high predictive value for rate of decline of the glomerular filtration rate (univariate P = 0.0003, multivariate P = 0.004) and end stage renal failure (P = 0.002 and P = 0.04). Baseline protein:creatinine ratios and rate of decline of the glomerular filtration rate were also significantly correlated (P < 0.0005). In the lowest third of the protein:creatinine ratio (< 1.7) there was 3% renal failure compared with 21.2% in the highest third (> 2.7) (P < 0.05). CONCLUSIONS: Protein:creatinine ratio in spot morning urine samples is a precise indicator of proteinuria and a reliable predictor of progression of disease in non-diabetic patients with chronic nephropathies and represents a simple and inexpensive procedure in establishing severity of renal disease and prognosis.     

Recurrent urinary tract infections. Biological suppositions and clinical treatment with thymopentin]

We estimated the glomerular filtration rate in 33 patients from our diabetic clinic using three methods: the creatinine clearance measured from a timed urine sample and a serum creatinine; the creatinine clearance calculated from the serum creatinine according to the formula of Cockcroft and Gault; and, the plasma clearance of ethylenediaminetetra-acetic acid (EDTA) labeled with 51Cr ([51Cr]EDTA). We repeated the measurements in seven subjects. The measured creatinine clearance was not reproducible. The other two methods were correlated, but not according to the formula y = x. The calculated creatinine clearance significantly underestimated the [51Cr]EDTA clearance particularly at higher [51Cr]EDTA clearance rates. [51Cr]EDTA clearance has been shown by others to parallel, but underestimate, inulin clearance, the optimal method of estimating glomerular filtration rate but difficult to perform in routine practice. Accurately measuring renal function in routine clinical practice is difficult, and this must be borne in mind when making clinical decisions based on current measurements.     

Long-term renal function in heart transplant recipients receiving cyclosporine therapy

BACKGROUND: Immunosuppression with cyclosporine has improved allograft function and reduced both morbidity and mortality in organ transplantation. However, cyclosporine-induced nephrotoxicity still is a concern. The purpose of our study was to evaluate the effects of cyclosporine on renal function in orthotopic heart transplant recipients. METHODS: Thirty-nine patients who received transplants from 1985 to 1991 and had at least three yearly glomerular filtration rate measurements posttransplantation by 125I-iothalamate clearance method were included in the study. In addition, serum creatinine (before and after transplantation) and cyclosporine doses were analyzed. RESULTS: Maintenance immunosuppression at 1 year consisted of prednisone (0.1 mg/kg/day), azathioprine (2 mg/kg/day), and cyclosporine (12-hour trough level 100 to 150 ng/ml by fluorescence polarization immunoassay). The mean serum creatinine at 1 year was significantly higher than the mean pretransplantation serum creatinine (1.51 +/- 0.32 versus 1.28 +/- 0.38, p < 0.05) and stabilized after the first year. The mean glomerular filtration rate by 125I-iothalamate clearance method was 70.6 +/- 20.3 ml/min/1.73 m2 (range 32 to 105) at 1 year and remained relatively stable during the follow-up period of up to 7 years. Creatinine clearance calculated by the Cockcroft and Gault formula overestimated the true glomerular filtration rate after the third year. The mean cyclosporine dosage was significantly lower after the first-year dose of 3.9 +/- 1.8 mg/kg/day (p < 0.05). Three patients in 39 started hemodialysis at 5, 7, and 10 years after transplantation. CONCLUSION: Our data indicate that the adequacy of renal function is preserved with long-term cyclosporine therapy in heart transplant recipients.     

Low dose angiotensin converting enzyme inhibition and glomerular permselectivity in renal transplant recipients

In this study, we determined the fractional clearance of neutral polydisperse dextrans (theta D) and monodisperse dextran sulfate (theta DS) to describe glomerular size and charge selectivity in 25 renal transplant recipients with proteinuria. Thirteen were treated with low dose lisinopril for six months (group 1) and 12 patients without ACE inhibitor therapy formed group 2. Mean arterial blood pressure was stable (group 1, 112 +/- 4; group 2, 109 +/- 2 mm Hg at baseline and after 6 months) whereas creatinine clearance, glomerular filtration rate and renal plasma flow decreased nonsignificantly but were comparable at any time. Lisinopril treatment lowered filtration fraction (22 +/- 2 vs. 19 +/- 2%, P = 0.07) whereas no change was seen in group 2 (20 +/- 2%). The fractional protein excretion (mg urinary protein per day/ml creatinine clearance per day) was stable in group 1, but significantly increased in group 2. The same pattern was found for theta D larger than 56 A. theta DS was stable and consistently elevated in both groups at any time. We conclude that low dose ACE inhibitor treatment in proteinuric renal transplant recipients stabilizes glomerular size selectivity independently of its systemic hemodynamic effects.     

Chronic renal failure and nephrolithiasis in a solitary kidney: role of intervention

PURPOSE: We determined the role of intervention and its outcome in patients with a solitary kidney, nephrolithiasis and chronic renal insufficiency, as well as the role of clearance in these patients compared to those with a solitary kidney, nephrolithiasis and normal renal function. MATERIALS AND METHODS: A total of 36 records was evaluable, including 16 from patients with normal (group 1) and 20 from those with abnormal (group 2) renal function. Group 2 was further subdivided into those with mild to moderate (group 2A) and advanced (group 2B) renal failure. Patients with acute renal failure were excluded from the study. Glomerular filtration rate was calculated by the Cockcroft and Gault formula. The reciprocal of serum creatinine was used to determine outcome. RESULTS: Groups 1 and 2 were comparable demographically except for serum creatinine, stone bulk and hospital stay. Of 36 patients 8 with normal renal function and 15 with chronic renal failure underwent percutaneous nephrolitholapaxy, 6 underwent extracorporeal shock wave lithotripsy and 7 underwent open surgery. Total clearance was achieved in 25 of 36 patients (72%). Glomerular filtration rate improved in 24 patients, remained stable in 8 and deteriorated in 4. However, 3 patients had less than 20% deterioration and 1 had significant deterioration in function after intervention. Improvement in glomerular filtration rate after intervention was significantly greater in cases of advanced renal failure. Patients with residual stones did worse than those without residual calculi. Mean hospital stay, deterioration in glomerular filtration rate and major morbidity rate were significantly greater in patients with residual calculi than in those with total clearance. CONCLUSIONS: Intervention should be contemplated in patients with a solitary kidney, stone disease and renal failure as in any other patient with stone disease, with the aim being total clearance. Stone eradication delays deterioration, and decreases the requirement for dialysis and renal replacement.     

The impact of a national impregnated bed net programme on the outcome of pregnancy in primigravidae in The Gambia

The effect of the non-ionic contrast medium iohexol (Omnipaque) on renal function was investigated in diabetic patients with signs of peripheral ischaemia. Forty-six patients, 70 +/- 11 years (mean +/- SD) old, age at diabetes diagnosis 53 +/- 17 years, and with varying degrees of diabetic nephropathy were studied before 1, 2, and 30 days after aortobifemoral arteriography. Serum creatinine, creatinine clearance, urinary excretion of immunoglobulin G, albumin collagen IV (NC1), kappa and lambda chains, alpha-1 microglobulin and Tamm-Horsfall protein were evaluated. Within 1 month before and 30 days after arteriography, the glomerular filtration rate was measured by clearance of iohexol. The acute effect of the radiocontrast medium was an increase in the serum creatinine level in 41 (89%) patients, with a more than 25% increase in 12 (26%) patients. The excretion rates of immunoglobulin G and albumin decreased, whereas the proximal and distal tubular function and the excretion of collagen IV did not change. The increment in serum creatinine was associated with the preangiographic renal function (p < 0.05), a history of heart failure (p < 0.01), but not with age, duration and type of diabetes, gender, systolic or diastolic blood pressure, glycated haemoglobin (HbAlc) or blood glucose levels. The increase of serum creatinine was associated with a pre-existing proximal tubular dysfunction and a worsening of distal tubular function. No changes in the parameters measured persisted 30 days after angiography. In summary, a transient increment in serum creatinine level after arteriography occurred in 89% of diabetic patients. It was associated with the preangiographic renal function, a history of heart failure and signs of preexisting proximal tubular dysfunction and worsening of distal tubular function. However, these changes were reversible.     

Predictability of creatinine clearance estimates in critically ill patients

OBJECTIVES: a) To evaluate the predictive ability of different creatinine clearance methods as compared with the criterion standard, inulin clearance; and b) to determine which of the predictive methods yields the most accurate estimation of creatinine clearance. DESIGN: Prospective study. SETTING: Medical intensive care unit (ICU) of a university-affiliated tertiary care hospital. INTERVENTIONS: Glomerular filtration rate was measured by the criterion standard, inulin clearance. PATIENTS: Twenty mechanically ventilated adults. MEASUREMENTS: Renal function was assessed by the following procedures: inulin clearance using a standard protocol, 30-min creatinine clearance, 24-hr creatinine clearance, and creatinine clearance estimates by the Cockcroft-Gault equation. Ideal body weight, total body weight or lean body mass with actual serum creatinine or serum creatinine concentration corrected to 1 mg/dL (85 mumol/L) in cachectic patients were sequentially incorporated into the Cockcroft-Gault equation. RESULTS: The Cockcroft-Gault equation, using ideal body weight and the corrected serum creatinine concentration, was the best predictor of inulin clearance with the smallest bias (9.7 +/- 8.6, 95% confidence interval 5.7 to 13.8). The bias encountered with the 30-min creatinine clearance was not different from that value with the 24-hr creatinine clearance (21.6 +/- 33.0, 95% confidence interval 6.2 to 37.1 vs. 25.4 +/- 28.3, 95% confidence interval 11.8 to 42.9). Good correlations existed between inulin clearance and the Cockcroft-Gault equation, using ideal body weight and the corrected serum creatinine concentration (r2 = .81; p = .0001), as well as between inulin clearance and the Cockcroft-Gault equation, using the lower of ideal or total body weight and the higher of the actual serum creatinine concentration or corrected serum creatinine (r2 = .75; p = .0001). The 30-min creatinine clearance and the 24-hr creatinine clearance had poorer agreement with inulin clearance. The incorporation of a corrected serum creatinine value into the Cockcroft-Gault equation consistently led to better predictions and higher correlation coefficients. CONCLUSIONS: The utilization of the Cockcroft-Gault equation as used clinically (the lower of ideal or total body weight and the higher of actual serum creatinine or corrected serum creatinine concentration to 1 mg/dL [85 mumol/L]) results in more accurate predictions of glomerular filtration rate in the medical, critically ill patient than urine creatinine clearance measures. If creatinine clearance measures are used, the 30-min collection provided results not different from those results obtained with 24-hr urinary collections.     

Cytokine inhibition preserves renal hemodynamic function following mesangial cell immune injury

BACKGROUND: We assessed the effect of a cytokine inhibitor, compound SKF 86002 (a bicyclic imidazole), on changes in renal hemodynamics (renal blood flow and glomerular filtration rate) that occur acutely following immune injury of glomerular mesangial cells. METHODS: Injury was induced in Munich-Wistar rats by the administration of a monoclonal antibody against the mesangial cell membrane antigen Thy 1.1. An acute drop in renal blood flow (RBF) and glomerular filtration rate (GFR) occurred within one hour of injury. RESULTS: Pretreatment of animals with the cytokine inhibitor SKF 86002 prevented this drop. SKF 86002 had no effect on glomerular synthesis of vasoconstrictor eicosanoids. CONCLUSIONS: The observations indicate that in mesangial cell immune injury, cytokines mediate renal hemodynamic impairment.     

Unilateral nephrectomy in dogs with renal disease: 30 cases (1985-1994)

OBJECTIVE: To evaluate indications for and complications, efficacy, and effects on renal function of unilateral nephrectomy in dogs with renal disease, and to evaluate the role that scintigraphy had in the decision to excise a kidney. DESIGN: Retrospective case series. ANIMALS: 30 dogs with renal disease that underwent unilateral nephrectomy. A comparison group of 12 dogs with renal calculi that underwent renal scintigraphy but not nephrectomy was included. RESULTS: Indications for nephrectomy included renal or ureteral calculi (n = 10), renal mass (8), chronic pyelonephritis (5), perirenal mass (3), severe hydronephrosis and hydroureter (3), and renal hypoplasia with ureteral ectopia (1). None of the dogs were azotemic before surgery. Renal scintigraphy apparently influenced the decision to perform nephrectomy, because in 14 of 16 dogs that underwent nephrectomy, the affected kidney contributed < or = 33% of the total glomerular filtration rate, but in 6 of 8 comparison dogs that underwent nephrotomy, the affected kidney contributed > 33% of total glomerular filtration rate. Complications of nephrectomy included oliguria (5) and organ laceration (2). Mean +/- SD final serum creatinine concentration for 16 dogs alive at least 6 months after nephrectomy was 2.2 +/- 1.8 mg/dl. Three dogs had chronic renal failure of undetermined cause at the time of death. Nephrectomy did not completely resolve the underlying disease in 13 dogs. Renal function was evaluated in 6 dogs 2 to 3.5 years after nephrectomy and was impaired in 4. None of the dogs were anemic, azotemic, proteinuric, or hypertensive. Survival time varied depending on the underlying disease. CLINICAL IMPLICATIONS: Multiple factors contributed to the decision to perform nephrectomy. Unilateral nephrectomy resulted in few serious complications and was not detrimental to the remaining kidney, but did not always resolve the underlying disease.     

Renal structural-functional relationships in early diabetes mellitus

To define the earliest renal morphological changes in patients with type I diabetes, we studied renal function and morphometric analysis of renal biopsies in 59 patients with diabetes for 5-12 years and normal blood pressure, normal creatinine clearance (CCr), and negative dipstick urinary protein. Arteriolar hyalinization and intimal fibrous thickening were noted in 43%. Glomerular basement membrane thickness and fractional mesangial volume were increased in 51% and 56%, respectively. The pre-pubertal and post-pubertal years of diabetes were associated with similar degrees of renal structural changes, but during the pre-pubertal years normal urinary albumin excretion (UAE) was seen. Principal factor analysis of morphometric structural parameters yielded four clusters of variables: "glomerular size" correlated with patient age, CCr, and UAE; "peripheral capillary decrease" correlated with glycosylated hemoglobin, diastolic blood pressure, glomerular filtration rate, and UAE; "mesangial increase" correlated with UAE; and "interstitial scarring" correlated with diastolic blood pressure. This study provides unique documentation of renal structural abnormalities which precede clinically evident renal functional abnormalities and documents that these early structural abnormalities are present in the pre-pubertal years of diabetes as well as postpuberty, and are associated with each other in constellations that correspond to postulated mechanisms in diabetic nephropathy.