Fibromuscular disease of the renal artery: a new histopathologic classification.

To evaluate the relationship between clinical, radiologic, and histopathologic features in various types of renal artery fibromuscular disease, the records of 37 patients operated upon for a total of 44 lesions of the renal artery (30 unilateral and seven bilateral) were retrospectively reviewed. Of these, 36 had hypertension associated with stenosis or aneurysm of the trunk or branches of the renal artery; one had aneurysm of the renal artery without hypertension. The histopathologic study included 38 arterial segments retrieved from 33 patients and underscored the difficulties in using topographic criteria to classify lesions. While all arterial aneurysms were associated with involvement of the media, more than one layer of the artery was involved in 65.7% of cases. Topographic forms, such as the perimedial type, were difficult to classify. Based on the study results, it appears essential to distinguish patients with fibrosis and smooth muscular hyperplasia (type I: 19 patients, 23 arteries) from patients with isolated fibrosis (type II: 14 patients, 15 arteries). In group II, preoperative hypertension was more long-standing (p less than 0.04), more lesions were extended distally (p less than 0.05), and the probability of recovery from hypertension at 52 months follow-up was lower. We have distinguished two different evolutive stages of fibromuscular disease of the renal artery, one characterized by fibrosis with smooth muscle hyperplasia and the second, associated with more severe prognosis, characterized by isolated fibrosis.