An assessment of anorectal motility in the management of adult megacolon

Symptoms and diagnostic criteria of acquired Megacolon - a systematic literature review

BACKGROUND

Acquired Megacolon (AMC) is a condition involving persistent dilatation and lengthening of the colon in the absence of organic disease. Diagnosis depends on subjective radiological, endoscopic or surgical findings in the context of a suggestive clinical presentation. This review sets out to investigate diagnostic criteria of AMC.

METHODS

The literature was searched using the databases - PubMed, Medline via OvidSP, ClinicalKey, Informit and the Cochrane Library. Primary studies, published in English, with more than three patients were critically appraised based on study design, methodology and sample size. Exclusion criteria were studies with the following features: post-operative; megarectum-predominant; paediatric; organic megacolon; non-human; and failure to exclude organic causes.

RESULTS

A review of 23 articles found constipation, abdominal pain, distension and gas distress were predominant symptoms. All ages and both sexes were affected, however, symptoms varied with age. Changes in anorectal manometry, histology and colonic transit are consistently reported. Studies involved varying patient numbers, demographics and data acquisition methods.

CONCLUSIONS

Outcome data investigating the diagnosis of AMC must be interpreted in light of the limitations of the low-level evidence studies published to date. Proposed diagnostic criteria include: (1) the exclusion of organic disease; (2) a radiological sigmoid diameter of ~ 10 cm; (3) and constipation, distension, abdominal pain and/or gas distress. A proportion of patients with AMC may be currently misdiagnosed as having functional gastrointestinal disorders. Our conclusions are inevitably tentative, but will hopefully stimulate further research on this enigmatic condition.

Rectal hyposensitivity

Rectal hyposensitivity (RH) relates to a diminished perception of rectal distension that is diagnosed during anorectal physiologic investigation. There have been few direct studies of this physiologic abnormality, and its contribution to the development of functional bowel disorders has been relatively neglected. However, it appears to be common in patients with such disorders, being most prevalent in patients with functional constipation with or without fecal incontinence. Indeed, it may be important in the etiology of symptoms in certain patients, given that it is the only "apparent" identifiable abnormality on physiologic testing. Currently, it is usually diagnosed on the basis of elevated sensory threshold volumes during balloon distension in clinical practice, although such a diagnosis may be susceptible to misinterpretation in the presence of altered rectal wall properties, and thus it is uncertain whether a diagnosis of RH reflects true impairment of afferent nerve function. Furthermore, the etiology of RH is unclear, although there is limited evidence to support the role of pelvic nerve injury and abnormal toilet behavior. The optimum treatment of patients with RH is yet to be established. The majority are managed symptomatically, although "sensory-retraining biofeedback" appears to be the most effective treatment, at least in the short term, and is associated with objective improvement in the rectal sensory function. Currently, fundamental questions relating to the contribution of this physiologic abnormality to the development of functional bowel disorders remain unanswered. Acknowledgment of the potential importance of RH is thus required by clinicians and researchers to determine its relevance.

Results of anal or low rectal anastomosis and pouch construction for megarectum and megacolon

Over a 16-year period 34 patients underwent surgery for idiopathic megarectum or megacolon; 18 had megarectum with or without megasigmoid, one megacolon only and 15 megarectum and total megacolon (nine with a previous colectomy). Ten patients underwent low rectal or anal anastomosis without pouch formation (colodistal proctostomy, eight; coloanal anastomosis, two), eight had colonic pouch-anal anastomosis (J pouch) and 14 had an ileal J pouch after restorative proctocolectomy; one underwent subtotal colectomy with ileorectal anastomosis and one loop ileostomy alone. There was one death, from intestinal obstruction 24 months after operation. Twenty-seven of 32 evaluable patients without a stoma became fully continent following resection and sphincter-saving procedures. Three of 18 had a poor result after resection for megarectum because of recurrent constipation. One of 14 patients became incontinent after restorative proctocolectomy for megacolon and megarectum and in a further four persistent abdominal distension and pain was treated by pouch excision.

Hirschsprung's disease in adolescents and adults

Hirschsprung's disease in the adolescent and adult is a rare and often misdiagnosed cause of lifelong refractory constipation. Two adolescent and three adult patients with Hirschsprung's disease treated between 1973 and 1987 at the University of Michigan Medical Center are reported. Each patient presented with chronic constipation requiring enemas, cathartics, and multiple hospital admissions for management. Diagnosis in each case was made with barium enema and full-thickness rectal biopsy. Four patients underwent endorectal pull-through procedures, all with good long-term results. The fifth patient, initially treated with a Duhamel retrorectal pull-through procedure, required reoperation for constipation secondary to a retained rectal septum. Review of 199 cases of adult Hirschsprung's disease enables comparison of the various operative procedures for this disorder with respect to postoperative complications and functional outcomes. Anorectal myectomy with low anterior resection, the Duhamel-Martin procedure, and the Soave endorectal pull-through procedure are the most acceptable methods for surgical management.

Randomized trial comparing anorectal myectomy and controlled anal dilatation for outlet obstruction

A randomized controlled study has compared anorectal myectomy (n = 13) with anal dilatation (n = 10) using Park's anal retractor for patients with constipation. No patient was able to defaecate spontaneously more than three times a week before the operation. Of the 13 patients, 7 were able to defaecate spontaneously more than three times a week after anorectal myectomy, compared with none after anal dilatation (P less than 0.05). None of the patients in either group became incontinent. There was a significant fall of anal canal pressure after anorectal myectomy at rest, during maximum pelvic floor contraction, and attempted defaecation: median, 100 (range, 21-200) to 43 (20-133) cmH2O, P less than 0.01; 140 (79-238) to 86 (43-153) cmH2O, P less than 0.01; 127 (79-208) to 86 (29-167) cmH2O, P less than 0.005. A significant improvement in rectal emptying occurred after anorectal myectomy (median, 0 per cent/min (range, 0-83) to 50 (0-100) per cent/min, P less than 0.025). On the other hand, anal dilatation was not associated with any significant change in rectal emptying or anal pressure. Pre-operative anal pressures during attempted defaecation in patients who achieved a good result after anorectal myectomy were significantly higher than those that did not (median, 136 (range, 120-208) versus 114 (79-129) cmH2O, P less than 0.025). Patients having a good result after anorectal myectomy had a significantly shorter history of constipation (median, 4 (range, 2-14) versus 38 (4-72) years, P less than 0.01) and normal colonic transit (median, 100 (range, 4-100) versus 10 (0-90) years, P less than 0.05) compared with those who had no benefit after operation.

Anorectal myectomy for outlet obstruction

Anorectal myectomy has been evaluated in 29 patients with chronic constipation associated with outlet obstruction. Eight patients had histological evidence of aganglionosis. No patient was able to defaecate spontaneously more than once a week before operation. Eighteen (62 per cent) patients were able to defaecate spontaneously more than 3 times a week after operation (good results) whereas 11 patients were not. There was a significant fall in maximum resting anal pressure after operation in the patients having a good result (102.7 +/- 16.7 to 79.5 +/- 27.8 cm H2O) whereas there was no significant fall in those having a poor result (118.4 +/- 25.0 to 108.8 +/- 28.5 cm H2O). The operation had no influence on squeeze pressures, length of the high pressure zone, rectal sensation or the anorectal angle. These results seem to indicate that the therapeutic effect of anorectal myectomy is merely due to reduced resting and canal pressures.

Function of the anal sphincters after chronic radiation injury

Anorectal manometry was done in 10 men with chronic radiation proctitis and symptoms of urgency, frequency, and occasional incontinence of faeces. They were compared with 10 asymptomatic age and sex-matched controls. The maximum resting anal canal pressure and the physiological sphincter length were significantly lower (p less than 0.01) in the irradiated group. The rectosphincteric reflex was absent in one patient and showed abnormalities of recovery in four others, who had received radiotherapy. The squeeze pressure of the external sphincter was not significantly different. These results indicate that dysfunction of the internal anal sphincter may contribute to patients' anorectal symptoms after pelvic radiotherapy. Histological evidence suggests that damage to the myenteric plexus is mainly responsible. The manometric function of the external sphincter remains relatively unaffected.