How is renin measured in the renal vein for patients with unilateral renal artery stenosis?

From the Guidelines

Renal vein renin measurement in patients with unilateral renal artery stenosis is performed through catheterization of both renal veins and the inferior vena cava, with blood samples collected to determine the renal vein renin ratio, which can help identify patients who may benefit from revascularization procedures. The procedure involves direct catheterization and collection of blood samples from within each renal vein and from the inferior vena cava cephalad and caudal to the renal veins at baseline, as described in the study by 1. Prior to the procedure, patients should discontinue medications that affect the renin-angiotensin system, such as ACE inhibitors, ARBs, and diuretics, for at least 2 weeks, and be kept on a dietary sodium intake of 100 to 200 mmol per day, as recommended by 1. The test is typically repeated after stimulation of renin release by administration of either oral captopril or furosemide, as noted in the study by 1. A renal vein renin ratio (stenotic kidney to contralateral kidney) greater than 1.4:1 is considered significant and suggestive of functionally significant renal artery stenosis, as reported by Hughes et al. in the study 1. However, the utility of renal vein renin measurements has been largely supplanted by noninvasive imaging modalities, and the test is now performed very infrequently due to its limited clinical utility and need for invasive catheterization, as stated in the study by 1. The more recent study by 1 highlights the limitations of renal vein renin assays, including high rates of false-negative and false-positive results, which further supports the limited use of this test in clinical practice. Therefore, the use of renal vein renin measurement should be carefully considered and reserved for specific cases where noninvasive imaging modalities are inconclusive or unavailable, as implied by the studies 1 and 1.

From the Research

Measurement of Renin in Renal Vein

• Renin measurement in the renal vein for patients with unilateral renal artery stenosis is typically performed by obtaining blood samples from the renal veins and measuring the plasma renin concentration 2, 3, 4, 5, 6.
• The renal venous renin ratio, which is the ratio of renin concentration in the affected kidney to the contralateral kidney, is often used to diagnose and predict the outcome of treatment for renovascular hypertension 3, 5, 6.
• Studies have shown that the affected kidney secretes both active and inactive renin, while the contralateral kidney suppresses renin secretion 3.
• The use of an angiotensin II antagonist, such as saralasin, can help confirm lateralization of renin secretion and demonstrate a potential for renin secretion in patients without obvious lateralization 4.

Diagnostic and Prognostic Value

• Renal venous renin determinations have been shown to have diagnostic and prognostic value in unilateral renal artery stenosis treated by surgery or percutaneous transluminal angioplasty 5.
• The renin secretion index has been found to have a higher sensitivity and predictive value for a successful outcome than the plasma renin activity ratio 5.
• However, the method has limitations, and other factors such as age, kidney function, and underlying arterial disease are also important prognostic factors 5.

Changes in Renal Vein Renin Activity

• Studies have shown that plasma renin activity is significantly higher in the ischemic kidney than in the contralateral kidney in patients with unilateral atherosclerotic renal artery stenosis 6.
• The ischemic and contralateral renal vein renin ratio has been found to be a significant predictor of blood pressure changes after renal artery stenting 6.
• Measurement of renal vein renin activity has been found to be useful in evaluating the effects of renal artery stenting on hypertension 6.