Abnormalities of renal function in the elderly.

Objective: To investigate the glomerular and proximal tubular renal function and the prevalence of urinary abnormalities in the elderly.

Design: Cross-sectional study.

Setting: General community in the city of São Paulo.

Participants: A population-based sample of 200 elderly subjects was randomly selected. Of these, 81 subjects (45 females and 36 males; mean +/- SD age: 73.7 +/- 6 years) accepted to undergo laboratory examination and were included in the study.

Main outcome measures: 24-h creatinine clearance (CCr), microalbuminuria, urinary retinol-binding protein (urRBP), leukocyturia, hematuria and total proteinuria.

Results: CCr was lower than 80 ml/min/1.73 m2 in 68% of the subjects. The median (range) CCr was 65 ml/min/1.73 m2 (21-112) in males and 77 ml/min/1.73 m2 (27-107) in females (p = 0.14). No individual had serum creatinine greater than 1.5 mg/dl. urRBP determination was normal in 79 of 81 subjects. The prevalence of microalbuminuria (> 20 micrograms/ml) was 31% (n = 25, 19 men and 6 women). These individuals presented higher mean systolic blood pressure (147 +/- 20 vs. 135 +/- 22 mmHg, p = 0.02) and mean serum creatinine (1.13 +/- 0.20 vs. 0.96 +/- 0.20 mg/dl, p < 0.01) than those without microalbuminuria. The prevalence of leukocyturia (> 10,000/mm3), hematuria (> 10,000/mm3) and total proteinuria (> or = 0.3 mg/dl) was 19%, 28% and 5% in males and 33%, 27% and 4% in females.

Conclusions: Glomerular dysfunction and urinary abnormalities are frequent features in the elderly, however, proximal tubular dysfunction is uncommon in this population.