An inguinal hernia is a protrusion of abdominal-cavity contents through the inguinal canal. They are very common (lifetime risk 27% for men, 3% for women), and their repair is one of the most frequently performed surgical operations. There are two types of inguinal hernia, direct and indirect, which are defined by their relationship to the inferior epigastric vessels. Direct inguinal hernias occur medial to the inferior epigastric vessels when abdominal contents herniate through the superficial inguinal ring. Indirect inguinal hernias occur when abdominal contents protrude through the deep inguinal ring, lateral to the inferior epigastric vessels; this may be caused by failure of embryonic closure of the processus vaginalis...