Megarectum: Physiological Observations

The investigation of these children whose condi-tion is often called megacolon or colonic inertia suggests to us that the important changes seem to be in the rectum, which merits consideration as a specific organ. It is surprising how normal the proximal colon remains and how well it packs the faeces into the accommodating rectum (Fig. 1) which after some years may reach up to the ribs. Dolichocolon may also be largely a matter of radiological technique. Fig. 2 shows such an appearance, and Fig. 3 shows the effect of tannic acid in the barium enema. The colon empties effectively leaving only a residuum in the rectum. Several organic and functional factors can initiate the syndrome we prefer to call megarectum. It presents clinically as gross constipation with eventual overflow incontinence and only leads to serious ill health if neglected for many years. The clinical picture and treatment have been discussed elsewhere (Nixon 1961a, b), and here it will suffice to reiterate the need for prolonged management and the need for training to a regular bowel habit. None of the cases discussed here had frank organic lesions such as anal stenosis or sacral nerve deficit. One of us (R.P.C.) has made investigations of the pathophysiology; these support the concept of a rectum so enlarged that a normal bolus does not cause a sensory stimulus; therefore there is the need to teach defaecation as a habit to be performed regularly with voluntary efforts. Barium enemas and sensation tests carried out some years ago (H.H.N.) by the method of Goligher and Hughes (1951) showed that treatment could reduce the size of the rectum and re-establish a normal sensory response. But recent cineradio-graphy (Dr. Siddaway) has shown that in some clinic-ally cured cases the rectum remains inert and is apparently emptied by the extrinsic force of raised intra-abdominal pressure on straining. The present observations have also shown that a * A paper read at a meeting of the British Association of Paediatric Surgeons in Sheffield, July 1963. stage of enlargement may be reached at which distension causes relaxation of the external sphincter before any sensation is felt, a situation clearly conducive to soiling. Porter (1961, 1962) has reported similar findings in adults.