MODEL RELEASED. Hernia operation. Surgical assistant checking a patient's intravenous (IV) drip during surgery to repair an epigastric hernia. A hernia is the abnormal protrusion of an organ or tissue through an opening. The most common site of hernias is the abdomen, when a weakness in the abdominal wall evolves into a localized hole, or 'defect', through which adipose (fat) tissue, or abdominal organs may protrude. An epigastric hernia occurs in the epigastrum, the upper central region of the abdomen.