ULTRASOUND DOPPLER TECHNIQUE AND THE RENAL ARTERIES: DIAGNOSTIC IMPACT OF THE ECHO ENHANCER SH U 508A AND A NEW RENAL‐HILIAR VELOCITIES INDEX
Authors: Chain S. , Herrera R.N. , Mercau G. , Klyver J. , Alonso S. , Abdo L. , Ochoa J. , Muntaner J. , Ronderos R. , Escudero. E. 
Published: February 2004

Introduction: Renal vascular hypertension (RVH) accounts for 1–5% of the total population of patients with high blood pressure. In addition, the prevalence between patients with coronary and peripheral vascular disease usually is greater to 40%. Several noninvasive methods for diagnosis have been used in hypertensive patients with a suspicion of renal arteries stenosis, such as color Doppler ultrasound. The incorporation of echo enhancers (EE) to the echographic technique has had a significant impact for the yield of the study.

Objective: To analyze the feasibility of total visualization of main renal artery with and without EE. To determine the sensitivity and diagnostic specificity of the conventional color Doppler parameters for the diagnosis of RVH: renal peak systolic velocity (RePSV), renal aortic ratio (RAR): RePSV/peak systolic velocity at the abdominal aorta (AoPSV), with and without EE. A new index of velocities was also proposed: the renal‐hiliar index (ReHi‐Index): RePSV/renal hilum peak systolic velocity (ReHiPSV), and was compared with conventional parameters in terms of sensitivity and specificity, using angiography as the gold standard method.

Materials and Methods: 77 patients were included (45 males, 32 females, mean age 54 years) between July 1998 and April 2003. Echo‐Doppler analysis was made with and without EE, comparing the feasibility of visualization of the renal arteries in all their passage: proximal, medium, and distal. Three different echo machines were used: Ving Med CFM 800 (2,5 MHz and 3,5 MHz transducer), Toshiba SSH 140‐A (2,5 MHz and 3,75 MHz transducer) and Hewlett Packard Image Point HX (2,5 MHz and 4,0 MHz transducer). An EE composed of 999 mg of galactose and 1 mgof palmitic acid by each gram of grains was used with 300 mg/mL concentration. The direct parameters measured in the main renal artery were the following: (1) RePSV: as the highest Doppler velocity measured in systole in the main renal artery. (2) RAR: as the rate between renal peak systolic velocity, RePSV, divided by aortic peak systolic velocity, AoPSV, measured at the abdominal aorta. (3) ReHi Index: the rate between RePSV and renal hilum peak systolic velocity, ReHiPSV, measured at the hilum in its extrarenal section. Stenosis was considered significant when RePSV > 200 cm/s, RAR > 3.5 and new renal‐hiliar Index >2.7. Renal angiography was performed in 16 patients with echographic diagnosis of renal artery stenosis. Statistical analyses included specificity, sensibility, and relative risk calculations on the three mentioned direct parameters. The Mantel‐Haenszel chisquare test was applied to analyze statistically significant differences between the discrete parameters.

Results: 77 patients were examined with conventional color echo Doppler technique with and without EE. All 151 of 151 the renal arteries segments, proximal, medium and distal, were observed with EE, (100% feasibility) and 137 of 151 without EE (91% feasibility) (p < 0.001). Renal angiography revealed severe stenosis in 16 arteries (>60%), 3 with moderate obstruction (40–59%), 10 normal, 2 occluded, and one absent.The diagnostic accuracy of the direct parameters for the diagnosis of severe renal stenosis was as follows: (1) RePSV > 200 cm/s; 94% sensibility, 77% specificity, RR 9.17 (p < 0.001). (2) RAR > 3.5: 69% sensibility, 100% specificity, RR 3.6 (p< 0.001). (3) New ReHi‐Index > 2.7: 94% sensibility, 92% specificity, RR 12.24 (p< 0.001). The values of urea and creatinine in blood before and after the intravenous administration of EE were similar (p<0.72), showing EE as a well‐tolerated product.

Conclusions: (1) The visualization feasibility of renal arteries improved significantly with the EE use, increasing from 91% to 100% (p < 0.001). (2) A new renal‐hiliar index (ReHi Index) was introduced, with improved sensitivity and very acceptable specificity in relation to conventional direct parameters like RePSV > 200 cm/s and RAR > 3.5 (p< 0.0001). (3) EE showed an excellent security profile in terms of renal tolerance, also allowing its use in patients with deterioration of the renal function.