The ilioinguinal nerve follows a course identical to that of the iliohypogastric nerve. It runs downward and forward between the transverse abdominis and internal oblique. It enters the inguinal canal by piercing the internal oblique to lie between it and the overlying external abdominal oblique aponeurosis. Within the inguinal canal, the ilioinguinal nerve descends inferior and lateral to the spermatic cord in the male, or the round ligament of the uterus in the female. As it emerges via the superficial inguinal ring, it provides sensory fibers to the anterior part of the external genitalia, and motor fibers to the lower part of the internal abdominal oblique and transverse abdominis. The ilioinguinal nerve may be absent or very small, and may join the iliohypogastric nerve.
In a study conducted by Rab et al.  on cadaveric specimens, the ilioinguinal nerve provided no sensory branches in 40% of examined specimens. In 30% of specimens it shared a branch with the genitofemoral nerve and was the principal nerve to the groin. In the remaining specimens it assumed a primary sensory function supplying the mons pubis, anterior part of the labia majora, inguinal crease, and root of the penis and anterior scrotum.
The ilioinguinal nerve may be damaged in lower quadrant surgical procedures, e.g., appendectomy, resulting in a weakness of the affected abdominal muscles, and predisposition to herniation. Similarly, the course of the ilioinguinal nerve and its genital branches varies considerably, rendering them prone to injury in the repair of an inguinal hernia. A direct inguinal hernia may also develop as a result of damage to the ilioinguinal nerve and subsequent wearing down of the abdominal muscles. Entrapment  of the ilioinguinal nerve within the inguinal ligament (ilioinguinal syndrome) may produce debilitating chronic pain in the cutaneous area of its distribution.
Postoperative persistent lower abdominal pain in the absence of gastrointestinal and or gynecologic workup should alert the surgeon to the possibility of ilioinguinal or iliohypogastric nerve entrapment. Painful recurrent neuroma  within the ventral abdominal wall can be avoided by neuroectomy using a retro-peritoneal proximal resection.
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