Hernia A hernia is a defect in the abdominal wall allowing abdominal contents to protrude out of the abdominal cavity. Trauma, surgery and increased intra-abdominal pressure caused by such conditions as pregnancy, obesity, weight lifting or tumors are risk factors for hernia formation. Inguinal hernia Inguinal hernias usually affect males and are classified as indirect or direct inguinal hernias. Indirect inguinal hernias are caused by improper closure of the tract developing as the testes descend into the scrotum before birth. A sac comprising abdominal contents protrudes through the internal inguinal ring into the inguinal canal. It often descends into the scrotum. Although indirect inguinal hernias are congenital defects, these often are not evident until adulthood, when increased intra-abdominal pressure and dilation of the inguinal ring allow abdominal contents to enter the channel. Direct inguinal hernias are acquired defects resulting from weakness of the posterior inguinal wall. Direct inguinal hernias usually affect older adults. Femoral hernias are also acquired defects in which a peritoneal sac protrudes through the femoral ring. These hernias usually affect obese or pregnant women. Inguinal hernias may produce no manifestations and are discovered during routine physical examination. These may cause a lump, swelling or bulge in the groin, particularly during lifting or straining. An inguinal hernia may cause sharp pain or a dull ache radiating into the scrotum. A palpable mass may be present in the groin, although it may be felt only with increased intra-abdominal pressure (as occurs during coughing) and invagination of the scrotum towards the inguinal ring. Complications The risk of complications is low with a reducible hernia. If the contents of a hernia cannot be returned to the abdominal cavity, it is said to be incarcerated. Contents of an incarcerated hernia are trapped, usually by a narrow neck or opening to the hernia. Incarceration increases the risk of complications, including obstruction and strangulation. Obstruction occurs when the lumen of the bowel contained within the hernia becomes occluded, much like crimping of a hose. A strangulated hernia develops when blood supply to bowel and other tissues in the hernia sac is compromised, leading to necrosis. The affected bowel infarcts; leading to perforation and contamination of the peritoneal cavity. Clinical manifestations of a strangulated hernia include severe abdominal pain and distension, nausea, vomiting, tachycardia and fever.