The role of manometry, electromyography and radiology in the assessment of intractable constipation.

An analysis is made of functional studies performed in 96 constipated patients to see how these studies influenced the choice of surgical treatment. All patients underwent anal manometry, and other investigations included colonic transit studies (56), anal sphincter electromyography (42) and defaecatory proctography (34). Additionally nine patients underwent full thickness rectal biopsy. The resting anal canal pressures of the patients studied were lower than controls, and fibre density studies on electromyography were abnormal in half the patients studied suggesting a degree of denervation of the sphincter muscles, which possibly related to chronic straining on the toilet. There was evidence of reduced rectal sensation as shown by an increase in the least perceived volume on balloon distension of the rectum, and in those with megarectum and/or megacolon an increase in maximum tolerated volume. The recto-anal inhibitory reflex was used to screen for adult Hirschsprung's disease, but in one patient the reflex was present despite absence of ganglia on full thickness rectal biopsy indicating the need for biopsy as the definitive diagnostic procedure. Delayed colonic transit using radio opaque markers was a necessary requirement before recommending colectomy, and delayed transit was demonstrated in 34% of the patients studied. Anismus on electromyography was found in 20% of the patients but there was poor correlation with failure of the anorectal angle to widen when bearing down on proctography. The investigations helped in the choice of treatment, but were difficult to interpret. They should be used in severe constipation when surgery is being contemplated.