A renin-secreting tumour sensitive to changes in central blood volume (presumably via sympathetics) but not to circulating angiotensin II.

1. A 17 year old female presented with severe hypertension, hypokalaemia and elevated levels of plasma renin activity due to a renin-secreting tumour. 2. Renin was responsive to posture, low sodium diet, saline infusion and frusemide, but relatively unresponsive to raising or lowering circulating levels of angiotensin II. 3. Renal venous renin levels lateralized to the side of the tumour with good contralateral suppression when measured with control of posture and avoidance of prior stimulation, with and without angiotensin converting enzyme inhibition. 4. Levels of atrial natriuretic peptide were elevated and responsive to posture, saline infusion and angiotensin infusion. 5. The tumour was evident on computerized tomography, but not on intravenous pyelography or renal angiography. 6. Responsiveness of renin secretion to normal stimuli in reninoma may make diagnosis difficult, and renal vein sampling under controlled conditions is necessary.