Ilioinguinal and Iliohypogastric Nerve Injection

The Ilioinguinal and iliohypogastric nerve injection, or nerve block, is a valuable diagnostic, prognostic, and therapeutic tool for managing groin and genital pain believed to be mediated via the relevant nerves.
==Anatomy==
The ilioinguinal (II), iliohypogastric (IH), and genitofemoral (GF) nerves, collectively referred to as "border nerves," are responsible for sensory innervation to the skin situated between the abdomen and thigh
The ilioinguinal nerve comprises of fibers from the L1 nerve root with a contribution of fibers from the T12 nerve root in about 25% of patients. It provides sensation to the skin of the inguinal region, small area of medial thigh, and the upper scrotum/labia. 
It follows a curvilinear course from the L1 and occasionally T12 somatic nerves, passing along the inside of the ilium's concavity. This nerve then continues to pass anteriorly within a fascial plane between the internal oblique and transverse abdominis muscles, where it is readily identified with ultrasound scanning. The Iliohypogastric Nerve also lies within this fascial plane.
At the anterior superior iliac spine level, the ilioinguinal nerve perforates anteriorly through the transverse abdominis muscle. Its terminal branches provide sensory innervation to the skin over the lower portion of the rectus abdominis muscle. Interconnections often exist between the ilioinguinal nerve and the adjacent iliohypogastric nerve, and occasionally the genitofemoral nerve.
The iliohypogastric nerve also receives ventral branches of the L1 spinal nerve, with additional fibers from the T12 spinal nerve. The iliohypogastric nerve arises along the superior lateral edge of the psoas major muscle. Following its emergence, the nerve traverses the quadratus lumborum muscle in an inferolateral direction, extending towards the iliac crest. Midway between the iliac crest and the twelfth rib, the nerve penetrates the transversus abdominis muscle, located superiorly to the anterior superior iliac spine. 
Subsequently, the iliohypogastric nerve adopts an inferomedial route, perforating the internal oblique muscle above the anterior superior iliac spine. The nerve then proceeds between the internal and external oblique muscles, puncturing the aponeurosis of the external oblique approximately an inch above the superficial inguinal ring. In the journey between the oblique muscles of the abdomen, the nerve bifurcates into the lateral and anterior cutaneous branches. 
==Indications and Efficacy==
The injection can have diagnostic and therapeutic roles, generally in the context of post-surgical neuralgia.
==Technique==
Ultrasound is the gold standard modality.
===Ultrasound Guided===
* Patient Position: Supine
* Ultrasound Technique: Use a high frequency linear ultrasound transducer
** Start with the anterior superior iliac spine as the initial bony landmark
** Identify the umbilicus and palpate
** Place the inferior portion of the ultrasound transducer over the anterior superior iliac spine with the superior margin of the transducer pointed toward the umbilicus
** Rotate the superior margin of the ultrasound transducer superiorly and inferiorly until the fascial plane between the internal oblique and transverse abdominis muscle is identified
** Identify the ilioinguinal and iliohypogastric nerves within this fascial plane
** Identify the deep circumflex artery that lies within the same fascial plane adjacent to the target nerve.
* Needle Approach: From a point just below the inferior border of the ultrasound transducer, move the needle in-plane towards the target nerve
** Visualize needle tip and ilioinguinal nerve in real time
** Place needle tip within the fascial plane adjacent to the ilioinguinal nerve
* Needle Type: 1.5 inch (3.8 cm), 22-gauge needle
* Injection Solution: Normal saline can also be used prior to confirm adequate position and spread within the fascial plane. Once happy with needle placement, 6-8 mL total volume consisting of local anesthetic, and if necessary, corticosteroid or dextrose. 
File:Ilioinguinal nerve injection probe position.jpg|To perform ultrasound guided ilioinguinal nerve block, the inferior portion of linear high frequency ultrasound transducer is placed over the previously identified anterior superior iliac spine with the superior margin of the transducer pointed directly in an oblique plane at the ulbilicus.
File:Ilioinguinal nerve block fascial plane.jpg|Oblique ultrasound image demonstrating the acoustic shadow of the anterior superior iliac spine and the muscles layers and facial plane containing the ilioinginal and iliohypogastric nerves.
===Landmark Guided===
* Patient Position: Supine
* Procedure:
** Identify the anterior superior iliac spine as the primary landmark
** Identify the umbilicus as the secondary landmark
** Prepare the skin overlying the identified landmarks with an antiseptic solution
** Insert the needle at a point just inferior to the anterior superior iliac spine, aiming towards the umbilicus
** Aspirate to ensure the needle is not in a blood vessel before injecting the anesthetic
* Needle Type: 1.5 inch (3.8 cm), 22-gauge needle
* Injection Solution: 5 mL of local anesthetic, and if necessary, 40-80 mg of methylprednisolone
==Complications==
The most feared complication of the anatomic landmark guided nerve block is the inadvertent placement of the needle too deeply, leading to the needle tip entering the peritoneal cavity. Ultrasound guidance clearly delineates the margin between the transverse abdominis muscle and the underlying peritoneal cavity. In addition, the use of ultrasound can help to avoid inadvertent damage to the deep circumflex iliac artery, which lies within the same fascial plane and in close proximity to the ilioinguinal nerve.
==Videos==
<youtube>https://www.youtube.com/watch?v=WJPH6Ij3StA</youtube>
==See Also==
Post-Inguinal Hernia Repair Chronic Pain
==External Links==
Ultrasound-Guided Blocks for Pelvic Pain - NYSORA
Simplified ilioinguinal injection - OA Text
==References==
Category:Pelvis, Hip and Thigh Procedures