[Pseudotuberculous pyelonephritis associated with staghorn calculus: a case report].

This report describes a 56-year old woman with an unusual form of chronic pyelonephritis mimicking tuberculosis on histopathological findings. She visited our hospital complaining of left flank pain. Left staghorn calculus and retroperitoneal abscess extending from the kidney were demonstrated on CT. No bacteria, including mycobacteria were identified in preoperative urine bacterial culture. Left nephrectomy with drainage of retroperitoneal abscess was performed. Microscopically, the nephrectomy specimen showed caseating granulomas, formed by epitheloid cells, highly suggestive renal tuberculosis. In spite of these findings, acid-fast bacteria were not revealed in the renal lesion nor the abscess, and cultures of the abscess for mycobacteria were also negative. Because of failure of identifying Mycobacterium tuberculosis, this case should be diagnosed as not renal tuberculosis, but pseudotuberculous pyelonehritis, which has been mentioned in recent literatures. Although this disease is not widely recognized, we must be aware of it to avoid unnecessary antituberculous therapy.