Abstract
A 30-year-old white woman with urinary frequency, left costovertebral angle pain and hematuria had left hydronephrosis, a marked decrease in bladder capacity and severe eosinophilic cystitis on biopsy. She was treated with a nonsteroidal anti-inflammatory drug and an antihistamine, with a dramatic, complete and rapid recovery. The nonsteroidal anti-inflammatory drug was believed to have been responsible for the favorable outcome, since antihistamines have not produced reliable benefits in this disease. Nonsteroidal anti-inflammatory drugs are recommended in cases of eosinophilic cystitis.