Transit studies and anorectal physiology tests can subdivide severely constipated patients into three groups: colonic inertia causing slow transit, obstructed defecation, and a combination of both. Patients with obstructed defecation may have mechanical outlet obstruction related to the presence of anatomic abnormalities such as a rectocele, or functional outlet obstruction. The principles of treating slow-transit constipation or obstructed defecation alone are generally agreed upon. The optimal treatment of patients with combined colonic inertia and obstructed defecation is controversial. Some advocate pre-operative treatment of obstructed defecation, some favor postoperative treatment, some feel that no treatment is required, and others exclude patients with obstructed defecation from colectomy.
Duthie and Bartolo58 carried out colectomy and IRA in 32 patients with slow colonic transit. These included 15 patients with slow transit as well as nonrelaxing pelvic floor, all of whom were able to evacuate normally after colectomy. The authors suggested that testing these patients in an unnatural environment when there is no desire to defecate was not helpful and resulted in overdiagnosis of anismus. Their results suggested that there was no contraindication to colectomy in combined slow transit and obstructed defecation.
We have observed a poor correlation between preoperative rectal evacuation as demonstrated by proctography and postoperative clinical obstructed defecation.9 A total of 34 patients undergoing colectomy had preoperative evacuation proctography. Normal preoperative proctography was found in only 10 of 23 patients who had normal postoperative evacuation and four of 11 patients with postoperative evacuation difficulties. Of the 34 patients undergoing proc-tography, 20 had preoperative obstructed defecation, and 13 of these 20 could defecate normally postoperatively. Of the remaining seven patients, three were improved with postoperative biofeedback. We have not found preoperative pelvic floor retraining with biofeedback to be helpful or indeed necessary in the majority of patients with obstructed defecation and colonic inertia. Our preferred treatment is to offer biofeedback to those patients with persisting postoperative symptoms of obstructed defecation.
Other studies have shown a poor functional result after subtotal colectomy in patients with untreated obstructed defecation. Kuijpers59 reported persistent constipation in two of four patients with combined colonic inertia and disordered evacuation compared with a successful outcome in two patients who had preoperative biofeedback. Another study compared 28 patients with slow transit alone, with 33 patients with slow transit and impaired evacuation, and found a significantly higher failure rate in the latter group (11% vs. 39%).32
Certain tests of pelvic floor function may have different predictive values of outcome after subtotal colectomy for patients with combined colonic inertia and nonrelaxing pelvic floor. One study from St. Mark's Hospital showed that the ability to expel a balloon was predictive of postoperative pain and laxative requirements after colectomy.60 However, preoperative evacuation proctogram and paradoxical contraction on straining using puborectalis electromyography were not predictive of symptomatic outcome.
Some authors advocate preoperative biofeedback for patients with combined abnormalities. Nyam et al18 reported successful postoperative evacuation in all 22 patients with combined abnormalities treated with preoperative biofeedback and then subtotal colectomy. They reported equal functional results and improvement in quality of life in patients with slow-transit constipation and patients with combined slow transit and obstructed defecation. Others have reported less favorable results: Bernini et al61 found that all 16 patients with combined colonic inertia and obstructed defecation successfully learned to relax the pelvic floor during straining, confirmed on electromyographic studies; seven patients had complete resolution of constipation but six still complained of persisting incomplete evacuation.
Surgical treatment of mechanical outlet obstruction at the same time as colectomy for inertia may improve functional results. Lahr et al44 advocated pelvic hiatal hernia repair (PHHR) in addition to colectomy in patients with outlet obstruction (due to herniation of the rectum through the hiatus of pelvic diaphragm on defecography) and colonic inertia. Fifty-
seven patients underwent total abdominal colectomy and PHHR, whereas 52 patients with colonic inertia alone underwent colectomy. Improvement in symptoms was equivalent in the two groups. Piccirillo et al16 added rec-topexy to total abdominal colectomy in 15 of 54 patients with rectoanal intussusception in addition to colonic inertia. They excluded all patients with puborectalis dysfunction from surgery, and attributed their 94% success rate to a more complete preoperative physiologic assessment.
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