The inguinal canal is much like a rectangular tube in that it consists of four walls with openings at both ends, described as follows (Figure 7-4):
The contents of the inguinal canal include the genital branch of the genitofemoral nerve (L1–L2), the spermatic cord in males, and the round ligament of the uterus in females. Additionally, in both males and females, the ilioinguinal nerve (L1) passes through part of the canal. The ilioinguinal nerve courses between the internal oblique and the transverse abdominis muscles and enters in the middle of the inguinal canal in both males and females. The ilioinguinal nerve exits the inguinal canal through the superficial inguinal ring with other contents that course through the inguinal canal.
When the anterior abdominal wall muscles contract, intra-abdominal pressure increases (e.g., forceful exhalation; coughing). This increase in pressure pushes the diaphragm up, forcing air out of the lungs. The inguinal canal, with its openings in the anterior abdominal wall, serves as a potential weakness when intra-abdominal pressure increases. When the posterior wall the inguinal canal weakens (e.g., in the elderly), an increase in intra-abdominal pressure may force the small intestine into the inguinal canal, resulting in a hernia
. To check for the presence of a hernia in males, the healthcare provider will insert a finger up into the scrotum to the superficial inguinal ring. The patient is instructed to increase intra-abdominal pressure by coughing. If the physician feels contact on the fingertip, a hernia is most likely present.
Hernias are classified as direct or indirect, with the inferior epigastric vessels serving as the differentiating landmark.