HDCN Article Review/Hyperlink

Krumme B, Blum U, Schwertfeger E, Flugel P, Hoellstin F, Schollmeyer P, Rump LC

Diagnosis of renovascular disease by intra- and extrarenal Doppler scanning

Kidney Int (Oct) 50:1288-1292 1996

The purpose of this study was to determine the diagnostic value of color duplex doppler ultrasound in diagnosing renal artery stenosis compared to digital arteriography. It was a prospective study in 135 hypertensive patients [one of the largest of such studies]. The authors used both peak systolic velocities and resistive index as measures of renal artery stenosis. The patient group was hypertensive [160/90 mmHg] and had an extremely wide range of serum creatinines 99.7 +/- 77.7 umol/liter, and ranged in age from 45 to 73 years. The duplex ultrasounds were performed according to fairly standard protocols. A side-to-side difference in resistive index (RI) of 0.05 TOGETHER WITH a peak systolic velocity (PSV) greater than 2 m/s was used to discriminate normal from stenotic renal arteries. The gold standard used was great`er than 50% stenosis by renal angiography,

In the 135 patients with 267 kidneys, 295 renal arteries were studied (some had multiple renal arteries). In 88 patients, 107 renal artery stenoses were identified by angiography 71 = unilateral and 17 bilateral stenoses. In 3 patients, by angio, 5 renal artery occlusions were detected. 93 of the diseased arteries were atherosclerotic while fibromuscular dysplasia (FMD) was present in 19. Of the 91 patients with disease renal arteries, 68 underwent dilatation or stent placement. BP was improved or cured in 51 of these Separately, the two sonographic measures were not very good at detecting RAS. For example, in only 51% of patients with bilateral RAS was there a greater than 0.05 difference in the resistive index (RI). However, combining this test with the peak systolic velocity measurement resulted in detection of 80% of such patients. Overall, using both RI and PSV criteria resulted in a positive predictive value of 88% and a negative predictive value of 92%. There seemed to be a "dose-response" relationship between %RAS by angiography and resistive index, which to a lesser extent, also was present with peak systolic flow, such that mean side-to-side difference in resistive index with a greater than 70% stenosis was 0.10. However, for each test, the range of values in each RAS category was quite broad. One interesting point was, that Doppler, especially the RI side-to- side seemed to be especially useful for picking up severe fibromuscular dysplasia lesions. This is understandable, given the younger age of such patients, although the incidence of bilateral lesions in RAS vs. FMD is not given.

Comment: This article is most provocative. It clearly appears that duplex doppler color ultrasound is becoming the screening test of choice for renal artery stenosis.

I have some specific questions about the paper:

1. How many technical failures were there? Most institutions currently have about a 12-15% technical failure rate; this is never mentioned in the paper. See the Blaufox metaanalysis in the J Nuclear Med, Jan 1996. Krumme's one statement about failures relates to using them as a 'negative' study. If one considers unidentified arteries as technical failures, 12 arteries were not identified by either peak systolic velocity or resistive index, suggesting an 11% failure rate.

2. 68 patients underwent angioplasty or stent placement [not mentioned in methods re indications] and 51 responded. Unfortunately, there is no discussion about what group of patients responded to dilatation or stent placement. Were these patients in the FMD group? Were they in the over 70% stenosis group, were they the most severely hypertensive? Were they the patients with renal insufficiency? The range of serum creatinines was very broad; was there any difference in response rate by creatinine clearance? Did any patients require surgery post intervention?

3. Were any renal artery ostial lesions stented?

4. The statistic used most frequently was the Mann-Whitney test suggesting very large data ranges. (Lionel Mailloux, M.D., North Shore University Hospital, Manhasset, NY)