Plasma renin activity and oxygen content along the renal veins in hypertensive patients.

Plasma renin activity (PRA) and oxygen content in three different locations in the renal veins were studied in 27 patients with suspected renin-dependent hypertension or during post-operative follow-up investigations after renal artery reconstruction. A significant decrease in PRA was found along the right renal vein but not along the left one. The oxygen content simultaneously measured was lower in the central parts of both renal veins than most peripherally, more on the right side than on the left one, indicating dilution of renal venous blood. An erroneous ratio between renal vein PRA of the affected and the contralateral kidney was found in two of 17 patients with unilateral renal artery stenosis when sampling from a central position in the renal vein. This indicates that a peripheral position of the catheter is important when sampling for renal vein PRA.