[A case of retroperitoneal fibrosis forming a pelvic tumor--a type of multifocal fibrosclerosis].

We experienced a case of retroperitoneal fibrosis with formation of a pelvic tumor. The patient was a 55-year-old female who showed right-side hydronephrosis on examination and was admitted to this department for consultation. Retrograde pyelography clearly showed that the hydronephrosis was due to lower ureteral obstruction resulting from a pelvic tumor. Ultrasound, CT and MRI showed a tumor adhering to the right posterior surface of the bladder, and it was thought that the tumor was probably malignant. Transdermal/transvesical needle biopsy and transvaginal needle biopsy showed a minimal invasion and allowed the diagnosis of retroperitoneal fibrosis to be made. Ureterolysis was not carried out, and the patient was treated with steroid monotherapy. She was begun on 30 mg of prednisolone, and administration was continued for approximately 3 months while gradually decreasing the dosage. On completion of administration, the intrapelvic tumor had completely disappeared, showing that treatment was markedly effective. The patient had a history of an orbital pseudotumor, and it was concluded that this was a rare case coming under the heading of multifocal fibrosclerosis.