Renovascular hypertension. New diagnostic and therapeutic procedures

Renovascular hypertension (RVH) remains a leading cause of potentially curable hypertension. Although RVH affects less than 1% of the unselected hypertensive population, between 10% and 35% of appropriately screened patients referred to specialised centres for problematic hypertension may prove to have renovascular disease. Advances in percutaneous transluminal renal angioplasty (PTRA) have renewed interest in developing better noninvasive screening tests for identifying patients with potentially correctable hypertension or renal impairment due to renovascular disease caused by either fibromuscular dysplasia (FMD) or arteriosclerosis. Duplex ultrasound with the two-dimensional Echo-Colour-Doppler technique for measurements of blood flow velocities in the renal interlobar arteries as expressed in the Pulsatility Index (PI) has been evaluated. Experimentally induced changes in renovascular resistance (RVR) in normotensives and in primary hypertensives were registered noninvasively by means of PI-measurements. A significant correlation between the absolute values of PI and RVR was found in hypertensives (r = 0.50, p < 0.002), but not in normotensives. In both groups, the changes of RVR due to angiotensin II infusion and ACE-inhibition were significantly correlated to the changes in PI (normotensives: r = 0.69, p < 0.001, primary hypertensives: r = 0.64, p < 0.001). Normally, the blood flow velocities as expressed by the PI in the renal vasculature of the two kidneys are equal. In hypertensive patients, PI was lower in kidneys with significant renal artery stenosis (RAS) than in kidneys without RAS (p < 0.001). Doppler signals were absent in all kidneys with renal artery occlusion. A bilateral low PI combined with normal side difference in PI may in hypertensive patients indicate bilateral RAS. RVH was correctly diagnosed in 84% of the patients and the presence of RAS in 94%. Provocative testing of an activated renin-angiotensin system by means of an angiotensin converting enzyme inhibitor (ACEI) constitutes the foundation for screening for RVH using gamma camera renography with 99mTc-DTPA as a glomerular filtration marker. In 20 consecutive patients with successfully treated RVH, one-third of the patients were not correctly diagnosed using ACEI-enhanced 99mTc-DTPA gamma camera renography, which indicates that some patients with RVH have compensatory mechanisms to maintain GFR after ACE inhibition. The relationship between the renin-angiotensin system and erythropoietin (EPO) production was studied in 20 patients with RAS and hypertension.(ABSTRACT TRUNCATED AT 400 WORDS)