Retroperitoneal fibrosis associated with Riedel's struma.

A case of retroperitoneal fibrosis with bilateral ureteral obstruction in association with Riedel's struma of the thyroid is reported. There has been a definite increase in incidence of retroperitoneal fibrosis, but with prompt recognition and adequate treatment the mortality rate has been decreased from the original 14%. The association of Riedel's struma with retroperitoneal fibrosis has been noted in the past and its association with sclerosing cholangitis has also been mentioned. It is not known whether Riedel's thyroiditis originates in the thyroid gland and spreads or whether true thyroiditis is part of a generalized process. The temporal relationship of thyroiditis and retroperitoneal fibrosis suggests an extension of fibrosis from the thyroid, but one cannot be sure which condition occurred first. Whatever the cause, the treatment remains the same as for retroperitoneal fibrosis from other causes.