Anatomic and pathologic findings at external phased-array pelvic MR imaging after surgery for anorectal disease.

Pelvic magnetic resonance (MR) imaging is useful for identification of postoperative changes, complications, and disease recurrence in patients who have undergone surgery for primary or recurrent anorectal disease. Commonly used interventions include treatment for anorectal carcinoma: anterior rectal resection with or without creation of different colic anastomoses and abdominoperineal excision with or without pelvic reconstruction (omentoplasty, placement of myocutaneous flaps). Other common interventions include treatment for inflammatory bowel disease (coloproctectomy with or without creation of an ileoanal anastomosis and ileal pouch) and treatment for fistulas (placement of flaps or setons). Postoperative anatomic changes and formation of scar tissue can usually be identified with consecutive MR imaging examinations. Pelvic MR imaging is an accurate technique for assessment of complications including anastomotic leakage, septic complications such as fistulas and abscesses, neoplastic recurrence, and other less common complications (perineal hernia, peritoneal pseudocyst). The sophisticated surgical procedures used in rectal surgery can alter normal anatomy and make image interpretation difficult. Thus, familiarity with the appearances of postoperative anatomic changes, complications, and tumor recurrence is essential for accurate MR imaging evaluation after surgery for anorectal disease.