Experimental study of neorectal physiology after formation of a transversecoloplasty pouch

Background: A novel transverse coloplasty pouch (TCP) with a larger neorect al volume than a straight coloanal anastomosis (CAA) but a smaller volume t han a short colonic J pouch (CJP) may improve short-term function after rec tal excision. Methods: Twelve pigs were investigated 6 weeks after complete rectal excisi on followed by reconstruction with a CAA, CJP or TCP. The results were comp ared with findings in the normal pig rectum. Results: The colonic transit times assessed by radio-opaque marker transit were 24 h for CAA, 60 h for CJP and 32 h for TCP. Non-operated control pig had a mean transit time of 46 h. Pigs that had a CJP developed colonic dila tation and substantial faecal impaction. Colonic electrostimulation induced an adaptive relaxation in the normal rectum but a pressure increase in all neorecta, particularly after CAA. The neorectal longitudinal smooth muscle layer in pigs with a TCP was significantly thicker than that in pigs with a CAA or CJP; its thickness was closest to that of the normal pig rectum. C olonic smooth muscle layers 10 cm proximal to the coloanal anastomosis, abo ve the neorecta, were significantly thicker after CJP than after CAA. or TC P formation. No significant difference in microcirculation was observed bet ween the three restorative procedures. Conclusion: Accelerated colonic transit and a lack of adequate relaxation u pon endoluminal pressure increase was associated with urgency and incontine nce after CAA. Delayed colonic transit, faecal impaction and ineffective mu scular hypertrophy due to pouch dilatation and constipation indicated evacu ation problems after CJP construction. Functional and morphometric data for TCPs suggested almost normal defaecation. Of the three restorative procedu res, the data for TCPs were most similar to those obtained in the normal pi g rectum at short-term follow-up.