Single lumen ileum with myectomy: a possible alternative to the pelvic reservoir in restorative proctocolectomy. An alternative procedure to construction of a pelvic ileal reservoir was assessed which avoids the need for a pouch, while providing an adequate rectal substitute and good continence. Thirty-six female adult beagles were allotted randomly to undergo total colectomy with (a) ileo-anal anastomosis alone, (b) ileo-anal anastomosis with two 15 cm myectomies, (c) ileo-anal anastomosis and myectomy with an ileo-ileal valve, or (d) ileo-anal anastomosis with a duplicated J pouch. The animals were studied before operation and at 4-weekly intervals for 20 weeks after operation. Mortality rates were similar. Ileal compliance was increased significantly by myectomy from 0.64 ml/mmHg (median, interquartile range 0.49-0.78) after ileo-anal anastomosis alone to 1.65 mmHg (1.16-1.93), P less than 0.01, an increase which was maintained. Ileal capacity was also increased both by myectomy and by the J pouch: ileo-anal anastomosis = 85 ml (75-100 ml), ileo-anal anastomosis and myectomy = 139 ml (116-156 ml), ileo-anal anastomosis and myectomy and ileo-ileal valve = 125 ml (range 85-145 ml), ileo-anal anastomosis and J pouch = 130 ml (range 75-165 ml) (P less than 0.01). Bowel function in the other three groups was markedly superior to ileo-anal anastomosis alone. Mean transit time was significantly less after ileo-anal anastomosis, 5.2 h (2.6-8.2 h) than after both ileo-anal anastomosis and myectomy, 10.5 h (9.6-13.9 h), P less than 0.05 and ileo-anal anastomosis and J pouch, 11.0 h (8.4-13.0 h), P less than 0.05, but addition of an ileo-ileal valve did not produce a further increase in transit time, 12.9 h (range 10.5-14.5 h), P = n.s. Myectomy of single lumen ileum may be a useful alternative to a pelvic ileal reservoir in restorative proctocolectomy. 