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PURPOSE: The extended outcome after kidney donation has been a particular concern ever since the recognition of hyperfiltration injury. Few published reports have examined donor renal outcome after 20 years or greater. Kidney transplantation has been performed at the Cleveland Clinic Foundation since 1963, at which there is extensive experience with live donor transplantation. We assess the impact of donor nephrectomy on renal function, urinary protein excretion and development of hypertension postoperatively to examine whether renal deterioration occurs with followup after 20 years or greater. MATERIALS AND METHODS: From 1963 to 1975, 180 live donor nephrectomies were performed at the Cleveland Clinic. We attempted to contact all patients to request participation in our study. Those 70 patients who agreed to participate in the study were mailed a package containing a 24-hour urine container (for assessment of creatinine, and total protein and albumin), a vial for blood collection (for assessment of serum creatinine) and a medical questionnaire. All specimens were returned to and processed by the Cleveland Clinic medical laboratories. Blood pressure was taken and recorded by a local physician. A 24-hour creatinine clearance and the Cockcroft-Gault formula were used to estimate renal function, and values were compared with an age adjusted glomerular filtration rate for a solitary kidney. RESULTS: Mean patient followup was 25 years. The 24-hour urinary creatinine clearance decreased to 72% of the value before donation. For the entire study cohort serum creatinine and systolic blood pressure after donation were significantly increased compared with values before, although still in the normal range. The overall incidence of hypertension was comparable to that expected in the age matched general population. There was no gender or age difference (younger or older than 50 years) for 24-hour urinary creatinine clearance, or change in serum creatinine before or after donation. Urinary protein and albumin excretion after donation was significantly higher in males compared with females. There were 13 (19%) subjects who had a 24-hour urinary protein excretion that was greater than 0.15 gm./24 hours, 5 (7%) of whom had greater than 0.8. No gender difference was noted in blood pressure, and there were no significant changes in diastolic pressure based on gender or age. CONCLUSIONS: Overall, renal function is well preserved with a mean followup of 25 years after donor nephrectomy. Males had significantly higher protein and albumin excretion than females but no other clinically significant differences in renal function, blood pressure or proteinuria were noted between them or at age of donation. Proteinuria increases with marginal significance but appears to be of no clinical consequence in most patients. Patients with mild or borderline proteinuria before donation may represent a subgroup at particular risk for the development of significant proteinuria 20 years or greater after donation. The overall incidence of proteinuria in our study is in the range of previously reported values after donor nephrectomy.

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African Americans (blacks) have a disproportionately high incidence of end-stage renal disease due to hypertension. The Modification of Diet in Renal Disease (MDRD) Study found that strict blood pressure control slowed the decline in glomerular filtration rate (GFR) only in the subgroup of patients with proteinuria. The present report compares the effects of blood pressure control in black and white MDRD Study participants. Fifty-three black and 495 white participants with baseline GFRs of 25 to 55 mL/min/1.73 m2 were randomly assigned to a usual or low mean arterial pressure (MAP) goal of < or = 107 or < or = 92 mm Hg, respectively. GFR decline was compared between randomized groups and correlated with the level of achieved blood pressure. The mean (+/-SE) GFR decline over 3 years in the low blood pressure group was 11.8+/-7.3 mL/min slower than in the usual blood pressure group among blacks (P=.11) compared with 0.3+/-1.3 mL/min slower among whites (P=.81) (P=.12 between blacks and whites). In both blacks and whites, higher baseline urine protein excretion was associated with a greater beneficial effect of the low MAP goal on GFR decline (P=.02 for both races). Combining both blood pressure groups and controlling for baseline characteristics, higher follow-up achieved MAP was associated with faster GFR decline in both blacks (P<.001) and whites (P=.002), with a sevenfold stronger relationship in blacks (P<.001). These secondary analyses support the prior recommendation for a lower than usual blood pressure goal (MAP < or = 92 mm Hg) in black and white patients with proteinuria (> 1 g/d). In addition, a lower level of blood pressure control may be even more important in blacks than in whites in slowing the progression of renal disease.

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The clinical practice of estimating creatinine clearance (Ccr) from a patient's serum creatinine value by use of various nomograms and prediction formulas is widespread. The predictive accuracy of such Ccr estimates as substitutes for measured values of glomerular filtration rate (GFR) has not been determined. In addition, the effect of patient physical parameters on GFR prediction accuracy has not been assessed. To investigate these issues, 500 predicted Ccr values from each of four versions of the formula of Cockcroft and Gault were statistically compared with GFR values measured by sodium iothalamate clearance (Cio) in 394 human subjects representing every level of renal function. We conclude that (1) the original formula of Cockcroft and Gault is an inaccurate predictor of GFR; (2) correction of the formula for patient physical parameters does improve its accuracy for GFR prediction; (3) the best formula is not accurate enough to replace laboratory measurement of GFR; and (4) GFR prediction inaccuracy is more often associated with extremes in patient age, weight, serum creatinine, body surface area, and measured GFR but may occur for any value of each of these parameters.

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