Current issues of ACP Journal Club are published in Annals of Internal Medicine


Diagnosis

Duplex ultrasound scanning of the renal arteries had 98% sensitivity and 98% specificity for diagnosing significant renal stenosis

ACP J Club. 1995 Nov-Dec;123:71. doi:10.7326/ACPJC-1995-123-3-071


Source Citation

Olin JW, Piedmonte MR, Young JR, et al. The utility of duplex ultrasound scanning of the renal arteries for diagnosing significant renal artery stenosis. Ann Intern Med. 1995 Jun 1;122:833-8.


Abstract

Objective

To determine the diagnostic properties of duplex ultrasound scanning of the renal arteries for identifying patients with ≥ 60% renal artery stenosis and for excluding patients with either normal renal arteries or < 60% stenosis.

Design

Blinded comparison of the results of duplex ultrasound scanning of the renal arteries with those of renal arteriography.

Setting

Large tertiary referral center in the United States.

Patients

102 patients (mean age, 63 y; 57% women) evaluated for possible renal artery stenosis who had both duplex ultrasound scanning of the renal arteries and renal arteriography. All patients had hypertension that was difficult to control, unexplained azotemia, or associated peripheral vascular disease, which gave them a high pretest likelihood of renovascular disease.

Description of Test and Diagnostic Standard

Patients were scanned with an Ultramark 9 HDI ultrasound machine (Advanced Technology Laboratories, Bothell, Washington) after a 12-hour fast. Patients were classified as having 0% to 59%, 60% to 99%, or total renal artery stenosis on the basis of the renal and aortic peak systolic velocities and their ratio. All renal arteriograms (the diagnostic standard) had at least 2 views of the renal artery, and the degree of stenosis was estimated by visual examination without knowledge of the ultrasonographic results.

Main Outcome Measures

Sensitivity, specificity, and likelihood ratios.

Main Results

In the studied population, the prevalence of ≥ 60% renal artery stenosis as determined by arteriography was 66%. Using this cut point in this population, duplex ultrasound scanning had an overall sensitivity of 98% (122 of 124 arteries {95% CI, 94.3% to 99.8%}*) and a specificity of 98% (62 of 63 {CI, 91.5% to 99.9%}*). {The likelihod ratio for a positive test was 61.9 (CI, 11.6 to 350.5), and the likelihood ratio for a negative test was 0.016 (CI, 0.005 to 0.058)}*. Ultrasound results differed from arteriographic results for 5 out of 187 examined arteries.

Conclusion

Duplex ultrasound scanning of the renal arteries had high sensitivity and specificity for identifying patients with ≥ 60% renal artery stenosis and for excluding patients with either normal renal arteries or < 60% renal artery stenosis.

Source of funding: None.

For article reprint: Dr. J. W. Olin, Department of Vascular Medicine, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA. FAX 216-444-7370.

*Numbers calculated from data in article.


Commentary

Renal angiography, the standard diagnostic procedure used to confirm the presence of renal artery stenosis before surgery or angioplasty, is associated with renal complications that include renal failure. Consequently, alternative but accurate screening procedures with minimal adverse effects have been sought. Captopril renal scans have shown promise toward achieving this goal (1).

A recent prospective study showed that patients with captopril-induced changes during preoperative scintigraphy had marked improvement in blood pressure control after revascularization (2). Preoperative scintigraphy, however, is operator-dependent, resulting in greater sensitivity and specificity in some academic centers than in community hospitals. The study by Olin and colleagues shows that duplex ultrasound scanning can have a sensitivity and a specificity of > 95% for detecting renal arterial lesions. Although this is impressive, it should be noted that these data were derived from a group of persons with severe hypertension that was difficult to control. Additionally, the study assumes a linear correlation between the degree of vessel stenosis and the severity of hypertension; this assumption is incorrect. Thus, the authors' arbitrary cut point of 60% for a stenosis of the renal artery is clinically limited. Duplex ultrasound scanning also is operator-dependent and time-intensive. Further studies are needed to determine both the utility of this screening test among the general population with hypertension and the test's ability to predict responsiveness to revascularization.

Until these promising preliminary findings for duplex ultrasound scanning are backed up by more definitive evidence, captopril scintigraphy should be used to screen for suspected renal artery stenosis.

George L. Bakris, MD
Rush-Presbyterian-St. Luke's Medical Center Chicago, Illinois, USA