c. Indirect inguinal (Zinner, 10/e, pp 479–572.)
An indirect inguinal hernia leaves the abdominal cavity by entering the dilated internal inguinal ring and passing along the anteromedial aspect of the spermatic cord. The internal inguinal ring is an opening in the transversalis fascia for the pas- sage of the spermatic cord; an indirect inguinal hernia, therefore, lies within the fibers of the cremaster muscle. Repair consists of removing the hernia sac and tightening the internal inguinal ring. A femoral hernia passes directly beneath the inguinal ligament at a point medial to the femoral vessels, and a direct inguinal hernia passes through a weakness in the floor of the inguinal canal medial to the inferior epigastric artery. Each is dependent on defects in Hesselbach’s triangle of transversalis fascia and neither lies within the cremaster muscle fibers. Repair consists of reconstructing the floor of the inguinal canal. Spigelian hernias, which are rare, protrude through an anatomic defect that can occur along the lateral bor- der of the rectus muscle at its junction with the linea semilunaris. An inter- parietal hernia is one in which the hernia sac, instead of protruding in the usual fashion, makes its way between the fascial layers of the abdominal wall. These unusual hernias may be preperitoneal (between the peritoneum and transversalis fascia), interstitial (between muscle layers), or superficial (between the external oblique aponeurosis and the skin).