Renal vein renin activity: a prospective study of sampling techniques and methods of interpretation.

Seventy patients undergoing renal arteriography were studied prospectively to define optimal techniques of renal venous sampling and to establish the most appropriate methods for interpretation of renal vein renin and activity (RVRA). Plasma renin activity values from the aorta, the antecubital vein and the lower inferior vena cava were nearly identical. The relationship between renal vein renin activity in the two renal veins was not influenced by lack of simultaneous sampling or by contrast administration. Thirty-one patients with normal arteriograms had a mean RVRA ratio (right over left) of 1.12 +/- .11 (mean +/- SEM) but RVRA difference (right minus left) of only 0.02 +/- .11 ng/ml/hr. In contrast 16 patients with "significant" (greater than 70%) narrowing of the main renal artery had a mean RVRA ratio (involved over uninvolved) of 4.3 +/- 1.2 and a mean RVRA difference (involved minus uninvolved) of 3.9 +/- 1.4 ng/ml/hr. Seven patients (22%) with normal arteriograms had "abnormal" RVRA ratios (greater than or equal 1.5) but corresponding RVRA differences within one standard deviation of the group mean. Thus the difference inRVRA between both renal veins may more accurately reflect a patient's renovascular status than does the corresponding RVRA ratio. An "abnormal" RVRA ratio alone inadequately indicates the presence of renal ischemia.