Interobserver variability in assessing renal artery stenosis by digital subtraction angiography

Four experienced observers independently assessed digital subtraction angiograms (DSA) of 134 renal arteries in 67 patients. Only the main renal arteries were evaluated. All patients were hypertensive and were screened for the existence of renal artery stenosis. The findings were classified in four categories: 0-49% stenosis; 50-99% stenosis; total occlusion, and fibromuscular dysplasia (FMD). As a measure of interobserver agreement, the kappa-statistic, which corrects for agreement by chance alone, was used. A kappa-value of 0.65 +/- 0.06 (kappa +/- SE) resulted for all observers and all categories. For category I a conditional kappa = 0.74 and for category II a conditional kappa = 0.69 was found. In cases of total occlusion (2 patients) or FMD (3 patients), all observers agreed upon diagnosis. We conclude that DSA is a reliable method for assessing renal artery stenosis if images of sufficient diagnostic quality can be obtained (93% of observations). It can be used as a screening method for renovascular hypertension and possibly for follow-up studies after surgical correction or after percutaneous dilatation of renal artery stenosis.