Urinary albumin excretion: a predictor of glomerular findings in adults with microscopic haematuria.

BACKGROUND Microscopic haematuria without proteinuria is a common clinical finding. When urological causes are excluded, usual findings on renal biopsy are IgA nephropathy (which can progress to end-stage renal failure) or thin basement membrane nephropathy (which has an excellent prognosis). A non-invasive test to discriminate between the two would be useful. AIM To examine the value of measurement of urinary albumin excretion in discriminating glomerular causes of microscopic haematuria in patients without proteinuria on urine dipstick tests. DESIGN Single-centre retrospective cross-sectional observational study. METHODS Adult patients who underwent renal biopsy for microscopic haematuria over a 6-year period from January 1994 were identified. Study entry required normal renal function, no proteinuria detected by dipstick, and urinary albumin excretion <300 mg/24 h. Patients with IgA nephropathy had follow-up for a mean of 58 months after biopsy. RESULTS Of 169 patients fulfilling study criteria, 119 (70%) had normoalbuminuria (<30 mg/24 h); 52 (30%) had microalbuminuria (30-299 mg/24 h). Of those with normoalbuminuria, 106 (89%) had thin basement membrane nephropathy or no glomerular abnormality. Thirteen (11%) had IgA nephropathy, and of 12 of these followed-up for a mean 64 months, none developed overt, dipstick-positive proteinuria. In contrast, 24 (48%) of those with microalbuminuria had IgA nephropathy, and of 22 followed-up for a mean 55 months, five developed overt proteinuria. DISCUSSION Urinary albumin excretion is an indicator of likely glomerular findings in microscopic haematuria, and may influence whether a renal biopsy is necessary.