Morphologic alterations associated with mechanical bowel preparation before elective colorectal surgery: A randomized trial

PURPOSE: The feasibility and safety of left-sided colorectal procedures with avoidance of mechanical bowel preparation has recently been demonstrated. Moreover, mechanical preparation has been associated with an increased risk for abdominal septic complications, including anastomotic leakage. This study was designed to determine whether mechanical bowel preparation is associated with histologic alterations in the colon. METHODS: Fifty patients ( mean age, 61 ( range, 45 - 78) years) scheduled to undergo elective colorectal surgery were prospectively randomized to receive mechanical preparation ( polyethylene glycol; Group 1) or no preparation ( Group 2) preoperatively. A macroscopically healthy segment of the bowel was excised at the proximal margin of the colectomy piece. A pathologist, blinded to the patient's group allocation, assessed various morphologic parameters. RESULTS: Indications for colectomy ( cancer and complicated diverticulosis) did not differ between groups. Bowel wall alterations were more frequent in patients who received a preparation. The most striking alterations associated with mechanical preparation were loss of superficial mucus (moderate-to-severe in 96 and 52 percent in Groups 1 and 2, respectively; P < 0.001) and epithelial cells (moderate-to-severe in 88 and 40 percent in Groups 1 and 2, respectively; P < 0.01). In addition, inflammatory changes, i.e., lymphocytes ( severe in 48 and 12 percent in Groups 1 and 2, respectively; P < 0.02) and polymorphonuclear cells infiltration ( severe in 52 and 8 percent in Groups 1 and 2, respectively; P < 0.02), were more prevalent after mechanical preparation. CONCLUSIONS: Mechanical bowel preparation is associated with structural alteration and inflammatory changes in the large bowel wall. Although bowel wall inflammation is a known risk factor for anastomotic leak, it remains to be elucidated whether these changes have a direct relation to the deleterious effect of mechanical bowel preparation in terms of abdominal morbidity.