Vomiting, Scar. As any surgical procedure, complications can occur. Post operative vomiting is the most common issue. Surgical case fatality runs 1-5/1000 while doing nothing runs much higher.
Gastric perforation. The most worrisome complication of pyloromyotomy is gastric perforation. This can result when the incision made to spread the hypertrophic pyloric muscle is extended too deeply, through the full thickness of the stomach wall.
Minimal. There are immediate operative complications such as injury to stomach, duodenum and surrounding structures. Post operatively there can be wound infections and breakdown. Again the chances are small in appropriate surgical hands. Long term there are really no complications.