Although most hernias involving the anterior abdominal wall or groin can be diagnosed easily by inspection and palpation, imaging is the principal means of detecting internal, diaphragmatic, and other nonpalpable or unsuspected hernias.1,2
Multidetector CT can reveal the precise anatomic site of the hernia sac, the contents of the sac, and any complications. These features are critical to the initial diagnosis and subsequent management of the condition. 3 The multiplanar capability of MDCT also offers exquisite detail of the abdominal wall, allowing wall hernias to be identified accurately.4
An abdominal hernia can be classified into one of three types. An external hernia (abdominal wall hernia) is caused by the prolapse of an intestinal loop, omentum, or mesentery through a defect in the wall of the abdomen and/or pelvis. An internal hernia involves the protrusion of the bowel through the omentum or mesentery and into a compartment in the abdominal cavity. A protrusion of the stomach, bowel, omentum, or mesentery into the chest is usually described as a diaphragmatic hernia.
Intestinal obstruction is the most common complication caused by hernia. It is observed on CT as the dilatation of proximal bowel loops, together with a reduced or collapsed bowel caliber distal to the obstruction. Incarceration refers to an irreducible hernia; that is, the hernia cannot be reduced or pushed back manually. This diagnosis may be made clinically. A strangulating small bowel obstruction, which occurs after a closed loop obstruction, may be identified on CT from wall thickening, engorgement of mesenteric vessels, mesenteric haziness, and ascites.5
ABDOMINAL WALL HERNIAS
Wall hernias are a common finding on abdominal imaging. Most abdominal wall hernias are asymptomatic, though they may cause acute complications that require emergency surgery. Prompt diagnosis is desirable, as delays in treatment are linked to significant morbidity.6 To avoid the chance of acute complications, this type of hernia will usually be repaired as an elective surgical procedure.7
• Inguinal hernia. Inguinal hernia, the most common type of abdominal hernia, may be subdivided further into indirect and direct inguinal hernias. Indirect inguinal hernias, which are found more often, occur lateral to the inferior epigastric vessels (Figure 1). They are observed in male children when the peritoneal extension accompanying the testis during embryonic development is not obliterated completely, and can form in adults owing to weakness and dilatation of the inguinal canal.8