The treatment of megacolon is mainly surgical. Laxatives or intestinal lavage are entirely palliative and are consequently indicated for patients in whom surgical intervention is either temporarily or permanently contraindicated. Dietary management is not generally worthwhile to improve symptoms. Excellent results are obtained with surgery as described by Duhamel45 in 1956 for the treatment of congenital megacolon.
The technique consists of an abdominal and perianal approach. After laparotomy, a sigmoid loop resection is performed, suturing the rectal stump as a Hartmann's operation. The retrorec-tal space is then dissected up to the tip of the coccyx. The perianal stage follows, with dissection of the submucosal space of the posterior hemicircumference of the anal verge extending 3 to 4 cm from the dentate line. At this level, the posterior rectal wall is incised, opening a communication from the submucosal space to the already dissected retrorectal space. The mobilized left colon is exteriorized through this dissected tunnel to the anal verge. The colon is fixed to the posterior mucocutaneous margin of the anal canal. The anterior pulled through colonic wall and the posterior rectal mucosa, which was previously dissected, are double clamped in a V-shaped fashion. The clamps are
left in place until they spontaneously fall apart, usually around the fifth postoperative day. This technique is illustrated in Figure 25.11, and the postoperative radiograph (enema) is shown in Figure 25.12.
In 1968, Haddad46 proposed a modification of the Duhamel's technique. This variation consisted mainly of replacement of the clamps by a perineal colostomy, which was resected together with the rectocolic septum in a second operative stage. The latter procedure is performed 7 to 10 days later. This operation has gained popularity throughout Brazil and most other South American countries.
In 1974, Moreira47 performed the Duhamel procedure in three patients with Chagasic mega-colon with a large megacolon, and instead of sigmoid resection, this enlarged bowel segment was pulled through the retrorectal space, with delayed lateral-lateral sigmoid-rectal anastomosis. Long-term follow-up demonstrated that regardless of megasigmoid resection, this surgical technique successfully corrected the constipation. Moreover, a progressive reduction of sigmoid diameter was demonstrated on subsequent contrast barium enema. Based on this result, the authors are encouraged that the Duhamel operation does help ameliorate the physiopathologic mechanisms of Chagasic megacolon.
Despite good results in the Duhamel operation for Chagasic megacolon, no consensus was found in the literature for the universal best surgical technique. At present, however, the authors prefer the Duhamel operation. From 1966, surgeons at the School of Medicine at the University of Goias, Brazil, exclusively performed the Duhamel procedure with several technical modifications48-51 on a total of 1145 patients
Figure 25.13. Patients operated for Chagasic megacolon through Duhamel's technique (1.145 cases) (Feb/1966 to Feb/2000).
operated between February 1966 and February 2000 (Fig. 25.13). Duhamel surgery, with an experienced surgical team, is associated with low recurrence rates (3%). Moreover, recurrent symptoms are rarely associated with dilatation of the pulled-through colon and are less severe than the preoperative condition. This may be caused by inappropriate surgical technique, including a long rectal stump or a low colorectal septum. The morbidity and mortality rates are unexpectedly low (15% and 1%, respectively), as these patients are usually severely ill with associated Chagasic cardiopathy and megae-sophagus, which ultimately results in severe mal-nourishment. Moreira52 performed anorectal manometry in patients with Chagasic mega-colon before and after the Duhamel surgery was undertaken. There was a statistically significant symmetric decrease in the postoperative anal resting and squeeze pressures compared to the preoperative values. As well, an improvement was also seen in the rectal sensory threshold (p = .030), rectal capacity was significantly decreased postoperatively (p = .029), and rectal compliance was improved (p = .027). Moreira concluded that Duhamel's surgery decreases sphincter pressures at rest and during voluntary contraction of the anal canal. It also improves the rectal sensory threshold, decreases both rectal capacity and compliance, and, ultimately, normalizes intestinal function.
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