Effect of bowel preparation and a fiber-free liquid diet on expression of transforming growth factor and procollagen in colonic tissue preoperatively and postoperatively.

Purpose: Dehiscence of colonic anastomoses is prevalent and potentially fatal. In an attempt to reduce the likelihood of anastomotic dehiscence, the colon is cleansed before surgery and fiber-free diets are prescribed postoperatively. However, fiber-free diets induce colonic atrophy and impair healing. This study was designed to investigate the effect of bowel preparation and postoperative fiber-free diet on the local gene expression of transforming growth factor-beta 1 and procollagen type I.

Methods: Four Sprague-Dawley rats underwent bowel preparation with a fiber-free liquid diet and polyethylene glycol in a balanced electrolyte solution for two days (fiber-free preoperative diet group), whereas four rats received standard chow with fiber (preoperative diet with fiber group). On the third day tissue was obtained from the descending colon of each rat to assess the effect of bowel preparation. Forty additional rats had their bowels prepared and underwent transection of the descending colon and anastomosis. These rats were then randomly assigned to continue on the liquid diet (fiber-free postoperative diet group) or rat chow (postoperative diet with fiber group). On postoperative days 3, 5, 6, 7, and 14, colonic tissue was obtained from the anastomosis and analyzed with the use of semiquantitative reverse transcriptase-polymerase chain reaction to examine the relative expression of transforming growth factor-beta 1 and procollagen type I genes normalized to that of a constitutive gene.

Results: There was a decrease in the expression of the transforming growth factor-beta 1 and the procollagen type I genes in the fiber-free preoperative diet group compared with the preoperative diet with fiber group; however, this difference only reached statistical significance for procollagen type I. Postoperatively, significant increases in the expression of the transforming growth factor-beta 1 and procollagen type I genes over baseline levels were observed around postoperative day 7 in both groups, which temporally correlates with active phases of collagen deposition in the wounded colon. Expression of the procollagen type I gene, however, was significantly decreased at this time in the fiber-free postoperative diet group compared with the postoperative diet with fiber group.

Conclusion: Although necessary to reduce septic complications, preoperative bowel preparation has a detrimental effect on the expression of transforming growth factor-beta 1 and procollagen type I. A postoperative fiber-free liquid diet also may be detrimental to the expression of these transcripts in the bowel. Alternative methods for delivery of colonic fuels are needed to create a better environment for colonic healing while eliminating bacteria and bulk.