Purpose: Myocutaneous flaps have documented efficacy in the reconstruction of complex perineal defects after tumor extirpation, but the utility of the omentum as a primary flap or as an additional flap has not been rigorously examined. Theoretical benefits of the omentum in pelvic floor reconstruction include providing vascularized tissue to a previously irradiated region, improving lymphatic drainage, and decreasing the risk of perineal hernia and bowel obstruction. The purpose of this study was to assess the usefulness and safety of the omentum in the reconstruction of complex perineal defects, following abdomino-perineal resection (APR) or pelvic exenteration for anorectal malignancy.

Methods: We performed a retrospective review of 51 consecutive patients who had APR or pelvic exenteration for anorectal malignancy, over a 4-year period, at a university teaching hospital. Patients were identified from a prospectively maintained cancer registry, and data regarding age, stage, medical co-morbidities, prior radiotherapy (XRT), method of reconstruction (primary repair, myocutaneous flap, and/or omental flap), and length of follow-up were collected. Main outcome measures included operative blood loss (EBL), length of stay (LOS), incidence and management of complications, and survival. Major complications were defined as intra-abdominal or pelvic abscess requiring drainage, hematoma requiring evacuation, bowel obstruction, need for re-operation, and flap loss. Patients who were reconstructed with omental flaps (n=22) were compared with patients who did not receive omental flaps (n=29), using Student's t test and chi-square analysis, with statistical significance assigned to p values < 0.05.

Results: From 2000-2004, 51 patients (mean age 58.7 years, range 32-86 years) with anorectal malignancy underwent APR (n=45) or pelvic exenteration (n=6). Incidence of major complications was significantly lower for patients who had omental flaps (4/22, 18%), compared to patients who did not have omental flaps (15/29, 52%) (*p=0.01). Complications in the omental flap group included perineal abscess (1), intra-abdominal abscess (2), perineal hematoma (1), and re-operation (3), with no morbidity related to the omental flaps. In contrast, complications in the non-omental flap group included perineal abscess (8), intra-abdominal abscess (2), reoperation (5), small bowel obstruction (4), fistula (1), and urinoma (1). Both groups were similar, in terms of age, stage, medical co-morbidities, XRT (39/51 patients), use of a myocutaneous flap, EBL (mean 914 ml), and survival. Myocutaneous flaps were used in 9/22 (41%) patients in the omental flap group, compared to 14/29 (48%) patients in the non-omental flap group, and included rectus abdominis (n=16), gracilis (n=5), and gluteus (n=2), plus 3 additional gluteal flaps for failed primary repairs (all in the non-omental flap group). Length of stay was slightly longer for the omental flap group compared to the non-omental flap group (14.1 vs 11.8 days), but this did not reach statistical significance. Mean length of follow-up was 304 days (range: 9-1597 days), with 50/51 patients surviving to discharge and 43/51 patients alive at the end of the study period.

Conclusions: Use of the omentum as a primary flap, or in combination with a myocutaneous flap, in the reconstruction of complex perineal defects is associated with a decreased incidence of post-operative complications. This documented efficacy strongly supports the use of the omentum in perineal reconstruction after APR or pelvic exenteration for anorectal malignancy.
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