Circular esophageal myotomy in the rhesus monkey: anatomical and physiological effects

Thirty-one rhesus monkeys were divided into six groups: a control group of 4 monkeys in which resection of 33% of the thoracic esophagus with end-to-end anastomosis was performed without myotomy, and test groups of 4 to 6 monkeys each in which circular myotomy in the proximal segment, distal segment, or both was combined with a 25% or 33% resection. In the control group, 2 of 4 monkeys survived. In the test groups, myotomy reduced longitudinal tension by 20 to 58%. Among the survivors were 4 of 6 animals that had 25% resection with proximal myotomy, 3 of 5 having 25% resection with distal myotomy, and 3 of 4 having 25% resection with combined proximal and distal myotomy. However, 4 of 5 monkeys that had 33% resection plus proximal myotomy and all 5 having 33% resection plus distal myotomy died of anastomotic leaks or strictures. Cineesophagography in surviving monkeys showed no motility disturbance at the myotomy sites. Manometry in 5 monkeys showed no change in resting lower esophageal sphincter pressure from that measured preoperatively. Postmortem examination in long-term survivors showed no stricture or dilatation at the myotomy sites. It is concluded that circular myotomy in the rhesus monkey reduces longitudinal tension, but compromise of the esophageal blood supply limits the usefulness of the procedure in bridging long gaps in the esophagus. Myotomy did not result in any motility disturbance or late anatomical sequelae, and therefore is still a valid procedure to facilitate the repair of short defects.