1. Returning the lower end of the esophagus to the abdominal cavity without tension is one of the main features of Mark IV surgery. For patients with short esophagus caused by esophagitis and those who have had esophageal surgery, it is relatively easy to surgically free the esophagus without tension and return the lower end of the esophagus to the abdominal cavity is one of the main features of Mark IV surgery.