The functional disorder of defecation after low anterior resection (LAR) was studied from the aspect of colonic motility in an experiment with dogs using a strain gage transducer, and the follwing results were obtained:
1) In early phase after LAR, the frequency of the colonic contractile waves increased at the proximal and distal sites of the anastomosis in both subgroups of dogs denervated and innervated of hypogastric and pelvic nerves. The increase was more remarkable at the distal site of the anastomosis. Also, the contractile waves were not propagated asross the anastomosis.
2) After LAR, strong colonic contractions occurred during defecation only at the distal anastomosis. Various patterns of contraction time required for defecation were demonstrated as compared to a single pattern in control dogs.
3) The frequency of the occurrence of colonic contractile waves and the propagation of the contraction tended to be normalized with time after LAR both in denervated and innervated groups, though the recovery was faster in the latter subgroup.
4) The frequency of defecation increased after LAR both in denervated and innervated groups compared to be in the control dogs, though more remarkable in the denervated groups. Although tended to be gradually normalized with time after LAR, the colectomized dogs required a long time for normalization of the frequency of defecation.
These results suggested the significant effect of reduction in reservoir space and disturbed continuity of intramural plexus caused by colectomy. Less severity, however, of functional disorder of defecation and earlier recovery from colonic motility disorder in the subgroup of the dogs innervated of autonomic nerves indicated usefulness of retaining autonomic nerves in colectomy.