The surgery is done while you are under general anesthesia (asleep and pain-free).
The surgeon makes a cut in the belly area. If the surgery is done using a laparoscope, three smaller cuts are made instead.
The surgeon cuts through some of the thickened muscle so it becomes wider.
The cut is then closed in a way that keeps the pylorus open. This allows the stomach to empty.
The surgery usually takes 1 - 2 hours.