Granulomatous interstitial nephritis: a clinicopathologic study of 46 cases from a single institution.

Acute interstitial nephritis is commonly seen in kidney biopsies of patients with acute renal failure; however, granulomatous interstitial nephritis (GIN) is rare. We identified 46 cases of GIN in a 17-year period in this institution and we investigated their most probable etiologies. Complete clinical information was available in 38 patients. Seventeen of 38 patients (44.7%) were classified as drug-induced. Renal sarcoidosis was responsible for 28.9% of cases, and the remaining 15.9% of cases included Wegeners granulomatosis, foreign body giant cell reaction, GIN secondary to intravesical bacillus Calmette-Guérin therapy for bladder cancer, and xanthogranulomatous pyelonephritis. Clinical investigation failed to reveal possible etiology in 4 patients (10.5%), classified as idiopathic. We concluded that three quarters of our cases were either drug-induced or due to sarcoidosis; only a small proportion of our cases occurred secondary to any other cause or to unknown factors.