Juxtaglomerular tumour: diagnostic renal vein renin measurements obscured by chronic captopril therapy.

A case of juxtaglomerular tumour (sometimes called hemangiopericytoma) in a 17 year old boy, presenting with severe hypertension and hypokalemia, is described. Plasma renin activity was markedly elevated in both renal veins and failed to lateralise the tumour. This is attributed to chronic stimulation of renin secretion by Captopril treatment. Removal of the tumour cured the hypertension and hypokalemia.