Anatomy of the ilioinguinal and iliohypogastric nerves with observations of their spinal nerve contributions.

Proper anesthesia and knowledge of the anatomical location of the iliohypogastric and ilioinguinal nerves is important during hernia repair and other surgical procedures. Surgical complications have also implicated these nerves, emphasizing the importance of the development of a clear topographical map for use in their identification. The aim of this study was to explore anatomical variations in the iliohypogastric and ilioinguinal nerves and relate this information to clinical situations. One hundred adult formalin fixed cadavers were dissected resulting in 200 iliohypogastric and ilioinguinal nerve specimens. Each nerve was analyzed for spinal nerve contribution and classified accordingly. All nerves were documented where they entered the abdominal wall with this point being measured in relation to the anterior superior iliac spine (ASIS). The linear course of each nerve was followed, and its lateral distance from the midline at termination was measured. The ilioinguinal nerve originated from L1 in 130 specimens (65%), from T12 and L1 in 28 (14%), from L1 and L2 in 22 (11%), and from L2 and L3 in 20 (10%). The nerve entered the abdominal wall 2.8 ± 1.1 cm medial and 4 ± 1.2 cm inferior to the ASIS and terminated 3 ± 0.5 cm lateral to the midline. The iliohypogastric nerve originated from T12 on 14 sides (7%), from T12 and L1 in 28 (14%), from L1 in 20 (10%), and from T11 and T12 in 12 (6%). The nerve entered the abdominal wall 2.8 ± 1.3 cm medial and 1.4 ± 1.2 cm inferior to the ASIS and terminated 4 ± 1.3 cm lateral to the midline. For both nerves, the distance between the ASIS and the midline was 12.2 ± 1.1 cm. To reduce nerve damage and provide sufficient anesthetic for nerve block during surgical procedures, the precise anatomical location and spinal nerve contributions of the iliohypogastric and ilioinguinal nerves need to be considered.