is the protrusion of an organ or the fascia of an organ through the wall of the cavity that normally contains it.
There are different kinds of hernia, each requiring a specific management or treatment.
By far the most common hernias develop in the abdomen, when a weakness in the abdominal wall evolves into a localized hole, or "defect", through which adipose tissue, or abdominal organs covered with peritoneum, may protrude. Another common hernia involves the spinal discs and causes sciatica.
A hiatal hernia occurs when the stomach protrudes into the mediastinum through the esophageal opening in the diaphragm.