Renal artery stenosis and nephrotic syndrome: a rare combination in an infant.

We describe an uncommon pediatric finding of unilateral renal artery stenosis, which presented as nephrotic syndrome, hypertension, failure to thrive, and hyponatremia. The child was a previously well 8-month-old male who looked well but had mild periorbital edema with severe hypertension. After 3 days of captopril therapy, the nephrotic-range proteinuria significantly improved. However, the hypertension persisted. Renal imaging revealed a small left kidney with reduced parenchymal uptake and no significant excretion. A renal angiogram demonstrated left renal artery stenosis with increased left renal vein renin activity. The hypertension resolved within 24 h of a left nephrectomy, but non-nephrotic-range proteinuria persisted for 8 months post operatively. Pathology of the left kidney was consistent with fibromuscular dysplasia. Although a few glomeruli (1%) had changes consistent with focal segmental glomerulosclerosis, such a few abnormal glomeruli were unlikely to account for the nephrotic syndrome. Hypertension-induced changes in the unaffected right kidney probably caused the nephrotic-range proteinuria.