Prevalence and causes of proteinuria in 20-year-old Finnish men.

The prevalence and causes of proteinuria were studied in a cohort of 36147 men aged 20 (born in 1956). Proteinuria was found in 139 men (0.4%) at the initial screening or examination. Further investigations reduced the number of proteinuria cases to 72 (0.2%). Persistent proteinuria was demonstrated in 46 men (0.13% of the series) and orthostatic proteinuria in 26 (0.07%). Urography revealed anomalies in 18 of 104 cases. Elevated blood pressure and reduced glomerular filtration rate were observed in a few men, mainly from the group with persistent proteinuria. Renal biopsy was performed in 61 cases--38 with persistent proteinuria, 12 with orthostatic proteinuria and 11 without proteinuria at the time of examination. Light microscopy gave normal findings or showed only slight mesangial or focal glomerulonephritis in the great majority of cases. Membranous, mesangiocapillary or chronic proliferative glomerulonephritis was present in one-fourth of the men with persistent proteinuria. This was the only group with such lesions.