The inguinal canal is a 4 cm oblique passage through the anterior abdominal wall, with four walls: the anterior wall (external oblique aponeurosis, reinforced laterally by internal oblique); the posterior wall (transversalis fascia, reinforced medially by the conjoint tendon); the superior wall/roof (arching fibres of internal oblique and transversus abdominis forming the conjoint tendon as they meet the inguinal ligament inferolaterally); and the inferior wall/floor (inguinal ligament and lacunar ligament medially). The deep inguinal ring is an opening in the transversalis fascia; the superficial ring is an opening in the external oblique aponeurosis.
The inguinal canal walls provide structural support to the inguinal region, allowing passage of the spermatic cord (males) or round ligament (females) from the retroperitoneum to the scrotum/labium while maintaining posterior abdominal wall integrity.
Understanding all four walls is essential for hernia surgery: direct inguinal hernias protrude through the posterior wall (transversalis fascia) within Hesselbach's triangle medial to the inferior epigastric vessels; indirect hernias protrude through the deep ring in the transversalis fascia lateral to the epigastric vessels. Lichtenstein tension-free mesh repair reinforces the posterior wall. TAPP and TEP laparoscopic hernia repairs place mesh posterior to the transversalis fascia, reinforcing all three potential hernia sites simultaneously.
Direct inguinal hernia protrudes through the transversalis fascia posterior wall medial to the inferior epigastric vessels within Hesselbach's triangle; indirect hernia enters the deep ring in the transversalis fascia lateral to the epigastrics and tracks along the inguinal canal within the spermatic cord coverings; distinguishing the two guides the repair approach in open surgery.
