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The abdominal wall consists of layers of fascia, muscle, and other tissues that together form one of the boundaries of the abdominal cavity. An abdominal wall hernia is a defect in one or more of these layers (primarily fascia) through which intra-abdominal tissues or organs can protrude.
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Hernias and hernia surgery are common, with over 20 million patients undergoing groin hernia repair alone each year worldwide. Hernias occur along a spectrum of clinical severity, from asymptomatic hernias detected incidentally on imaging studies to those associated with serious complications, such as bowel obstruction or necrosis. Although management of asymptomatic or minimally symptomatic hernias can include a watch-and-wait approach, the principal treatment is surgical repair.
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Hernias are categorized based on the anatomic location of the fascial defect. Groin hernias (consisting of inguinal and femoral hernias) are the most common, followed by ventral hernias (hernias of the umbilicus, epigastrium, and surgical incision sites). Other less common types of hernias include flank and pelvic hernias.
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Beyond their anatomic location, hernias can be further characterized by whether the protruding tissues or organs are trapped within the hernia. In a reducible hernia, the protruding contents can be returned to their normal anatomic location either spontaneously or with manual pressure. In contrast, the contents of an incarcerated hernia cannot be reduced. While incarceration does not necessarily imply that the hernia contents are obstructed or ischemic, it is typically a prerequisite for these complications to occur. Bowel obstruction can occur if the fascial defect through which a segment of bowel protrudes is narrow enough to cause its blockage through extrinsic compression. A strangulated hernia occurs when the blood supply to the hernia contents is compromised, resulting in ischemia.
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Several additional definitions are important to remember. In a Richter hernia, only part of the circumference of the bowel wall (usually the antimesenteric portion) becomes incarcerated. This type of hernia can be difficult to detect prior to intestinal necrosis with resultant peritonitis developing, as symptoms of bowel obstruction are typically absent. A sliding hernia occurs when a portion of a retroperitoneal organ—typically the cecum, sigmoid colon, or bladder—comprises a part of the hernia sac protruding through the fascial defect. Sliding hernias are most often seen in groin hernias and can make their repair more challenging, with increased risk of damage to the bladder or bowel. Hernias are also classified based on whether they occur at the site of a prior surgical incision—called an incisional hernia—or are associated with a stoma—called a parastomal hernia.
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The anatomy of the groin is complex, replete with confusing terminology, and subject to ongoing investigation and debate. This section focuses on structures critical in groin hernia repair and on terminology (including eponyms) standard in the surgical lexicon.