A hernia is the protrution of an organ or the fascia of an organ through the wall of the cavity that normally contain it. A hiatal hernia occurs when the stomach protrudes into the mediastinum through the essophageal opening in the diaphragm. By far the most common hernia develop in the abdomen,when a weakness in the abdominal wall evolves into a localized hole,or "defact",through which adipose tissue,or abdominal organs covered with peritoneum,may protrude