Anatomy - Transabdominal preperitoneal patch (TAPP) repair of inguinal hernia

Posterior aspect of the inguinal region: (1) Inferior epigastric artery and vein, (2) Medial orifice = direct inguinal hernia, (3) Femoral hernia orifice, (4) Pectineal ligament (Cooper), (5) Spermatic duct, (6) External iliac artery and vein, (7) Testicular artery and vein, (8) Iliopubic tract, (9) Lateral orifice = indirect inguinal hernia The inguinal region (where the anterior abdominal wall transitions to the lower extremity) possesses several weak spots, where a hernia sac (with or without contents) may protrude through the abdominal wall (femoral hernias are more frequent in women, while inguinal hernias are more common in men). Inferior to the inguinal ligament the septum of the iliopectineal arch divides the inguinal canal into a vascular and muscular compartment – lacuna vasorum and lacuna musculorum respectively. Vascular compartment

• Both the external iliac artery and vein (→ femoral artery and vein; with the artery lateral to the vein) course through the vascular compartment which is lateral to the pubic bone. In addition, the femoral branch of the genitofemoral nerve passes through the very lateral part of this compartment, while the deep inguinal lymph nodes (Rosenmueller nodes) are located inferomedially. In femoral hernias the lacuna vasorum is the deep weak spot (through the femoral septum along the femoral vein).

Muscular compartment

• Lateral to the lacuna vasorum, the muscular compartment is traversed by the psoas major and iliacus muscles (together they comprise the iliopsoas muscle), the femoral nerve, and lateral femoral cutaneous nerve.

During testicular development the tubular structure of the inguinal canal is formed by the externalization of the testicles, which are pulled into the scrotum by the gubernaculum testis. The peritoneum pulled along during this descent remains in the inguinal canal as a pouch (processus vaginalis testis). Thus, the layers of the abdominal wall turn into the corresponding sheaths in this pouch: Transversalis fascia → internal spermatic fascia, internal oblique → cremaster, fascia of external oblique → external spermatic fascia, no investment by the transversus abdominis since it terminates more cephalad. The blood vessels (testicular artery and vein), spermatic duct (ductus deferens) and nerves (ilioinguinal nerve originating from the lumbar plexus) are also pulled into the scrotum, and together they form the spermatic cord. When the processus vaginalis closes, it obliterates the connection with the peritoneal cavity, typically leaving behind only the vestige of the vaginal process. In the female embryo the pull of the gubernaculum does not result in a complete descent of the ovaries, which remain close to the uterus, but rather the remains of the original gubernaculum persist in the inguinal canal as the round ligament of uterus. Incomplete obliteration of the processus vaginalis is a weak spot in the abdominal wall and therefore a possible starting point for inguinal hernia. The approximately 4 cm long oblique inguinal canal, slanting downwards and medially, parallels the inguinal ligament immediately superior to it, with the cephalic end of the canal originating at the deep inguinal ring and the opening to the external abdominal wall at the superficial inguinal ring.

Deep inguinal ring

• Halfway between the pubic symphysis and the anterior superior iliac spine in the inner abdominal wall, lateral to the inferior epigastric artery and vein (within the lateral umbilical fold)

Superficial inguinal ring

• Superior to the pubic tubercle in the fascia of the external oblique, anterior edge pointing cephalad, posterior edge formed by inguinal ligament, sides = medial and lateral crus with stabilizing intercrural fibers.