[Role of CT and RM in postoperative evaluation of the patient after rectal carcinoma surgery: postoperative anatomy and nonneoplastic sequelae].

The CT and MRI findings in a series of 57 patients submitted to curative surgery for rectal cancer, 1989 to 1993, and locally free of disease at the time of examination, were retrospectively reviewed. Both postoperative anatomy and tissue repair features were studied relative to the different surgical approaches, i.e., rectum amputation, sphincter-saving resection, Hartmann technique. The retrospective analysis of CT and MR findings led to the identification of some signs rather typical of every predictable non-malignant postoperative event, with max accuracy when radiologic findings were correlated with clinical and laboratory findings, as well as with the results of baseline study performed about 3-6 months after surgery. Florid granulation tissue exhibited marked enhancement after i.v. contrast agent administration and high signal intensity on T2-weighted MR scans: such questionable findings as a pseudonodular pattern were often clarified on multiplanar MR images by the identification of normal anatomic structures within repairing scar tissue. The major features exhibited by fibrosis were low signal intensity on T2-weighted MR scans, laminar or spindle-like shape and some retraction of the surrounding tissues. Poor enhancement after i.v. contrast agent administration proved to be a less reliable diagnostic criterion. Abscesses were identified because of their water-like content and ring of peripheral enhancement, both easily demonstrated on CT scans. The differential diagnosis of necrotic colliquative recurrence required clinical correlation with a careful morphologic analysis of lesion outline. Non-colliquative inflammation exhibited no typical CT/MR features suggestive of diagnosis. Finally, radiation fibrosis was characterized by laminar pattern but its enhancement patterns and MR signal behavior were quite different from postoperative scar tissue: irregular enhancement spots and fairly high signal areas were often observed in these patients even months and years after radiation exposure.