Studies in Hirschsprung's disease.

The morbid anatomy of Hirschsprung's disease is now firmly established. Swenson and Bill (1948) noted that the dilated colon which figures so largely in the earlier description of the disease terminated at a point proximal to the anus and was followed by a spastic segment. They concluded that the obstruction was due in some way to this segment and that the hypertrophy and dilatation of the bowel above was secondary to this obstruction. Further work by Zuelzer and Wilson (1948), Bodian, Stephens and Ward (1949), Whitehouse and Kernohan (1948) and Swenson, Rheinlander and Diamond (1949) has shown that in the narrowed spastic segment there is a complete absence of the ganglion cells which form Meissner's and Auerbach's intramural plexuses. Instead there are large bundles of non-medullated nerve fibres occupying the position of the plexuses. This aganglionic segment extends from the anus up to the dilated part of the bowel. Examination of the dilated colon itself shows that there is hypertrophy of the muscle walls, but that the intramural ganglion cells are present in the normal quantities and arranged in the normal manner. The abnormalities of function of this aganglionic segment are less clearly defined. Barium enema shows that this segment extends from the anus to the rectosigmoid junction or distal sigmoid colon; it appears narrow and can sometimes be seen to undergo segmentation. Proximal to this segment the bowel enlarges to form the typical megacolon. Using a technique which involves the recording of intracolonic pressures by means of multiple balloon at various levels in the lower bowel, Swenson et al. (1949) showed that there was increased tone with an absence of normal peristalsis in the narrowed segment. Davidson, Sleisenger, Steinberg and Almy (1955) described the effect of mecholyl on the activity of the colon in Hirschsprung's disease as recorded by catheters in the lumen of the gut. They noted that in records taken from the aganglionic segment of six patients with Hirschsprung's disease, mecholyl produced no change; whereas in 20 normal subjects there was no change in 11, and relaxation of the bowel in nine. In discussing their results they noted the possibility of using this method for mapping out the aganglionic segment of intestine, and they also commented on the absence of any increased sensitivity of the intestine to cholinergic drugs, such as is found in the aganglionic part of the oesophagus in achalasia of the cardia, and such as would be expected from Cannon's law of denervated structures. They conclude that this is due to the lesion being congenital rather than acquired. It seemed that there was room for further investigation of the changes in the colon which occurred in Hirschsprung's disease. In the experiments which are described below, various properties of intestinal muscle obtained at operation from the aganglionic segment of gut from patients with Hirschsprung's disease and from a similar region in normal controls were examined to determine more accurately the nature of the derangement of function. The following investigations were carried out: (1) The response of the muscle strips to the action of various drugs in vitro; (2) The response of muscle strips in vitro to electrical stimulation at various voltages and duration of stimulation; (3) The presence or absence of ganglion cells in all specimens examined by the above methods was checked by ordinary histological means.