EFFECT OF BOWEL PREPARATION AND A FIBER-FREE LIQUID DIET ON EXPRESSION OF TRANSFORMING-GROWTH-FACTOR AND PROCOLLAGEN IN COLONIC TISSUE PREOPERATIVELY AND POSTOPERATIVELY

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 p ostoperatively. However, fiber-free diets induce colonic atrophy and i mpair healing. This study was designed to investigate the effect of bo wel preparation and postoperative fiber-free diet on the local gene ex pression of transforming growth factor-beta 1 and procollagen type I. METHODS: Four Sprague-Dawley rats underwent bowel preparation with a f iber-free liquid diet and polyethylene glycol in a balanced electrolyt e solution for two days (fiber-free preoperative diet group), whereas four rats received standard chow with fiber (preoperative diet with fi ber group). On the third day tissue was obtained from the descending c olon of each rat to assess the effect of bowel preparation. Forty addi tional rats bad their bowels prepared and underwent transection of the descending colon and anastomosis. These rats were then randomly assig ned to continue on the liquid diet (fiber-free postoperative diet grou p) or rat chow (postoperative diet with fiber group). On postoperative days 3, 5, 6, 7, and 14, colonic tissue was obtained from the anastom osis and analyzed with the use of semiquantitative reverse transcripta se-polymerase chain reaction to examine the relative expression of tra nsforming 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 procollage n 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. Postoperativ ely, significant increases in the expression of the transforming growt h 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 co lon. Expression of the procollagen type I gene, however, was significa ntly decreased at this time in the fiber-free postoperative diet group compared with the postoperative diet with fiber group. CONCLUSION: th ough necessary to reduce septic complications, preoperative bowel prep aration has a detrimental effect;on the expression of transforming gro wth factor-beta 1 and procollagen type I. A postoperative fiber-free l iquid diet also may be detrimental to the expression of these transcri pts in the bon el. Alternative methods for delivery of colonic fuels a re needed to create a better environment for colonic healing while eli minating bacteria and bulk.