Urinary Albumin Excretion Rate and Glomerular Filtration Rate in Single-Kidney Type 2 Diabetic Patients

OBJECTIVE To evaluate the urinary albumin excretion rate (UAER) and the glomerular filtration rate (GFR) of single-kidney type 2 diabetic patients (SKD) and of single-kidney non-diabetic patients (SKN).

RESEARCH DESIGN AND METHODS Patients who had only one kidney for at least 5 years, with no renal disease or hypertension at the time of the nephrectomy and with no calculus or systemic disease at the time of the evaluation, were included in this controlled cross-sectional study A total of 20 SKD (8 men, age 62 ± 9 years; diabetes duration 8.5 ± 7 years), 17 SKN (2 men, age 57 ± 13 years), and 184 type 2 diabetic patients who were matched to the single-kidney diabetic group for age, sex, and BMI were studied. UAER was measured by immunoturbidimetry in timed 24-h sterile urine, and GFR was determined by the ⁵¹Cr-EDTA single-injection method.

RESULTS SKD patients presented a higher proportion (8 of 20, 40%) of microalbuminuria (UAER 20-200 μg/min) than SKN patients (3 of 17, 17.6%) and type 2 diabetic patients (37 of 184, 20%). SKD patients presented a higher proportion of macroalbuminuria (UAER >200 μg/min; 6 of 20, 30%) than SKN patients (1 of 17, 6%) but were similar to type 2 diabetic patients (43 of 184, 23%). The GFRs of normoalbuminuric SKN (71.7 ± 21.4 ml · min⁻¹ · 1.73 m⁻²) and SKD patients (73.0 ± 21.5 ml · min⁻¹ · 1.73 m⁻²) were similar but higher than the one-kidney GFR (GFR ÷ 2) of the age-, sex-, and BMI-matched normal individuals (50.5 ± 9.0 ml · min⁻¹ · 1.73 m⁻²) and normoalbuminuric type 2 diabetic patients (54.0 ± 11.6 ml · min⁻¹ · 1.73 m⁻²).

CONCLUSIONS Increased GFR related to single-kidney status confers an increased risk of developing renal disease in the presence of diabetes.