Perirectal inflammatory disease: CT findings.

The findings on computed tomographic (CT) scans were reviewed in 42 patients with perirectal inflammatory disease and suspected perirectal abscesses. CT was reliable for use in distinguishing perirectal abscesses from cellulitis and in localizing both supralevator and infralevator abscesses. CT allowed correct diagnosis of 13 surgically proved perirectal abscesses in ten patients, including three with residual abscesses after surgical drainage. In three patients with supralevator abscesses, the abscess was missed on initial surgical exploration. In patients without abscesses, CT was helpful in evaluating the extent of perirectal inflammation; however, it was not possible to determine its cause. The anatomy on CT scans of the pararectal spaces is reviewed, with emphasis on useful anatomic landmarks in the axial plane for distinguishing supralevator from infralevator abscesses.