A hernia is the protrusion of a loop or portion of an organ or tissue through an abnormal opening, usually in the abdominal wall (in the groin, or inguinal region, alongside the artery supplying the thigh, through an unhealed, surgical incision) or in the diaphragm. Hernias can also occur internally, when the bowel protrudes through a narrow opening or pocket in the peritoneum, the abdomen’s internal lining.
Bowel protruding into a hernia can become entrapped, causing an obstruction or damage to the bowel. Surgical repair is usually recommended for hernias.
During an ascent, a trapped segment of bowel containing gas will expand; it could rupture and compromise its blood supply. For this reason, individuals should not dive with an unrepaired hernia.
In a hiatal hernia, part of the stomach protrudes into the chest cavity through the diaphragm’s esophageal opening. Two main types of hernia are distinguishable, since they have different implications for fitness to dive.
In a sliding hiatal hernia, the upper portion of the stomach slides upward in the space occupied by the esophagus. This hernia, found in a large percentage of North American adults, can cause gastroesophageal reflux, but it often has no symptoms. A paraesophageal hernia is a protrusion of the stomach through a separate opening of the diaphragm.
Significant gastroesophageal reflux should be treated before diving, but a sliding hiatal hernia does not by itself contraindicate diving. Part of the stomach can become trapped within a paraesophageal hiatal hernia, and, during ascent, could rupture. Thus, paraesophageal hiatal hernia is considered a contraindication to diving.
A few who have had surgical repair of their hiatal hernia (e.g., fundoplication) can suffer from gas-bloat syndrome, which is associated with gaseous distension of the stomach. This is believed to occur due to one’s inability to expel swallowed air by belching. During an ascent, this distension can also lead to gastric rupture. The symptom usually resolves within a few weeks. If the distension persists, however, diving is not advised.