RESUMEN
Fifty-six patients with unilateral hydronephrosis were the subject of this study. The patients were classified into 4 groups according to the stage of hydronephrosis as assessed by radiological criteria. Split kidney function, histopathological studies, and measurement of intraureteral pressure were performed. Urinary Bilharziasis was held responsible for obstructive nephropathy in 77% of cases. Complicating urinary infection was present in 66%. The study has shown that creatinine excretion was slightly decreased in early, moderate, and moderately advanced hydronephrosis. On the other hand, a marked lowering of urine osmolality was found even in the early stages of hydronephrosis. The hydronephrotic kidney was found to be a salt losing one only in early, moderate, and moderately advanced hydronephroses, but not in the very advanced cases. The histopathological changes were mainly tubular, but some cases showed proliferative changes in the glomeruli. Eradication of urinary Bilharziasis and early treatment of this disease would markedly contribute to the prevention of obstructive nephropathies in countries where this disease is endemic.