[A case of pleural involvement followed by idiopathic retroperitoneal fibrosis].

We report a rare case of pleural involvement followed by idiopathic retroperitoneal fibrosis in a 55-year-old man. He complained of right chest pain and his chest radiogram showed pleural thickening and calcification. Chest X-ray computed tomogram (CT) also showed a mass-like pleural thickening and a soft tissue density lesion surrounding the thoracic aorta, suggesting fibrosis. By open pleural biopsy, the mass-like pleural lesion was diagnosed as chronic pleuritis. Three years later, the patient experienced difficulty in urination, and bilateral hydronephrosis which was probably due to a retroperitoneal lesion was detected. Abdominal X-ray CT revealed a retroperitoneal lesion of soft tissue density comprised of a smooth and clearly delineated mass which encased the large vessels and ureters, compatible with retroperitoneal fibrosis. Although it was not possible to biopsy the retroperitoneal lesion, the lesion was clinically and radiologically thought to be retroperitoneal fibrosis. We could not determine the etiology of these findings, but such a case of pleural involvement followed by idiopathic retroperitoneal fibrosis was considered to be very rare.