Diagnostic role of new Doppler index in assessment of renal artery stenosis

Abstract

BackgroundRenal artery stenosis (RAS) is one of the main causes of secondary systemic arterial hypertension. Several non-invasive diagnostic methods for RAS have been used in hypertensive patients, such as color Doppler ultrasound (US). The aim of this study was to assess the sensitivity and specificity of a new renal Doppler US direct-method parameter: the renal-renal ratio (RRR), and compare with the sensitivity and specificity of direct-method conventional parameters: renal peak systolic velocity (RPSV) and renal aortic ratio (RAR), for the diagnosis of severe RAS.MethodsOur study group included 34 patients with severe arterial hypertension (21 males and 13 females), mean age 54 (± 8.92) years old consecutively evaluated by renal color Doppler ultrasound (US) for significant RAS diagnosis. All of them underwent digital subtraction arteriography (DSA). RAS was significant if a diameter reduction > 50% was found. The parameters measured were: RPSV, RAR and RRR. The RRR was defined as the ratio between RPSV at the proximal or mid segment of the renal artery and RPSV measured at the distal segment of the renal artery. The sensitivity and specificity cutoff for the new RRR was calculated and compared with the sensitivity and specificity of RPSV and RAR.ResultsThe accuracy of the direct method parameters for significant RAS were: RPSV >200 cm/s with 97% sensitivity, 72% specificity, 81% positive predictive value and 95% negative predictive value; RAR >3 with 77% sensitivity, 90% specificity, 90% positive predictive value and 76% negative predictive value. The optimal sensitivity and specificity cutoff for the new RRR was >2.7 with 97% sensitivity (p < 0.004) and 96% specificity (p < 0.02), with 97% positive predictive value and 97% negative predictive value.ConclusionThe new RRR has improved specificity compared with the direct method conventional parameters (RPSV >200cm/s and RAR >3). Both RRR and RPSV show better sensitivity than RAR for the RAS diagnosis.

Doppler ultrasound and renal artery stenosis: An overview

“…The RRR values, when compared to the other direct-method parameters (PSV > 200 cm/s and RAR > 3) showed a sensitivity and specificity of 97% and 96%, respectively. The main limitation of this study was that Chain et al [23] evaluated only the main RAs because these vessels have a more important role in renovascular diseases and could be submitted to endovascular treatment, while results obtained by other authors [10] using the parameters PSV and RAR included accessory RAs detected at arteriography. Recently, Li et al [27] found that receiver operating characteristic (ROC) curve analysis for RAS !…”

“…In one study, a RAR of 3.5 or greater identified hemodynamically significant lesions with a sensitivity and specificity of 91e92% and 75e95%, respectively [21,22]. In another study by Chain et al [23], a diagnosis of severe RAS based on RAR >3 yielded a sensitivity of 77%, specificity of 90%, PPV of 90% and NPV of 76%. In a recent study, RAR > 3.5 yielded a sensitivity and specificity of 91% and 91%, respectively [24].…”

“…a ratio of PSV measured in the renal artery to that obtained in the interlobar artery, was more accurate (sensitivity 88%; specificity 88%). Chain et al [23] proposed a new direct-method Doppler parameter, the renal renal ratio (RRR), which was defined as the rate between renal artery peak systolic velocity (RPSV) at the proximal or mid segment of the RA and RPSV measured at the distal segment of the renal artery (RRR Z RPSV (proximal or mid RA)/RPSV (distal RA). It is based on the fact that increased blood flow velocity through the stenosis and the immediate poststenotic segments and the observed decrease in blood flow velocity distal to the stenosis is proportional to the degree of stenosis.…”

“…In the detection of RAS, it is helpful to notice the degree and location of stenosis, arterial tortuosity and factors that influence PSVs in the abdominal aorta and RA. Accessory RAs are quite common, seen in approximately 25e30% of cases [23]. Two or more RAs are common, although typically one is dominant.…”

“…In angiographic investigations, the caliber of the single renal artery originating from the abdominal aorta was found to measure between 5 and 10 mm in adults, with values for women in the lower part of the range [23]. Aytac et al [24] showed that if the diameter of a RA measured by US is 4.65 mm or less, the presence of an accessory renal artery can be established with 80% sensitivity and 80.5% specificity.…”