Computed tomography in the differential diagnosis of the enlarged retrorectal space.

The value of computed tomography (CT) in the differentiation of an enlarged retrorectal space was analyzed in 132 cases. Classification of barium enema findings into those with simultaneous mucosal alterations and those without any visible lesions of the rectal mucosa seems to be useful. Computed tomography helps in those cases without mucosal changes to differentiate between retrorectal fibrosis, tumorous masses, and inflammatory diseases of the colon. It also demonstrates the lack of pathologic lesions in equivocal cases of pelvic lipomatosis and so-called "normal variants." If simultaneous mucosal involvement on barium enema--especially in rectal carcinoma or recurrent carcinoma of the rectum--is found, CT may show the perirectal extension of tumorous masses and thus help to clarify local operability.