Ultrasound-guided ilioinguinal block

IntroductionIlioinguinal nerve block is commonly used for inguinal procedures such as inguinal herniorrhaphy, orchidopexy and hydrocoele repair. It is also useful for pfannenstiel incision e.g. hysterectomy, ureteric reimplantation. In the pediatric population, controversy exists regarding the choice of ilioinguinal block versus caudal block for this surgery. Initial studies failed to demonstrate superiority from either technique. 1-4 A more recent study showed a reduction in stress hormone levels with caudal analgesia. 5 The popularity of caudally administered clonidine and ketamine has added further controversy with a recent study using caudally administered bupivacaine and ketamine showing more prolonged postoperative analgesia than fascial click ilioinguinal block. 6 However, the potential neurotoxicity of ketamine for this route needs to be clarified before routine use. Many practitioners place a caudal block for these procedures because the caudal block is relatively simple and has a high success rate. Potential advantages of the ilioinguinal block include a low incidence of postoperative leg weakness provided low volumes are used, and the ability to place the block with the patient in the supine position. Furthermore, ilioinguinal block represents an alternative to caudal block in children in whom anatomical variants render a caudal block contraindicated or impossible. With US guidance, as little as 0.075 mL/kg of local anesthetic can reliably block both the ilioinguinal and iliohypogastric nerves. 7 Reducing the total volume of local anesthetic is likely to reduce the spread of local anesthetic below the inguinal ligament and therefore the incidence of unwanted femoral nerve blockade and therefore leg weakness. 8 In addition to unwanted femoral block, ilioinguinal block has been associated with bowel perforation, 9 colonic puncture 10 and pelvic haematoma. 11 In one report this was complicated by intestinal obstruction. 12 It has been suggested that with ultrasound guided needle placement, the risk of intestinal perforation may be reduced. 13


Anatomy: Both the ilioinguinal and iliohypogastric nerves arise from the L1 root of the lumbar plexus. Both nerves supply the inguinal region including the spermatic cord and round ligament, the upper part of the scrotum, penis and labia. The position of these nerves relative to the muscles is highly variable. Medial to the anterior superior iliac spine the two nerves run between the internal oblique and transversus abdominis muscles, but later pierce internal oblique to lie deep to external oblique aponeurosis. In infants, the two nerves lie less than 0.5 cm medial to the anterior superior iliac spine. 14 The iliohypogastric nerve gives off a lateral cutaneous branch at the level of the anterior superior ilac supine, therefore, the block is more effective if performed at or proximal to this readily palpable landmark. The genital branch of the genito-femoral nerve, which at this level lies deep to the internal oblique muscle, also supplies the inguinal region. Additional blockade of the genito-femoral nerve results in more complete intra-operative anesthesia, but is not essential for effective postoperative analgesia. 15

Skill level: Simple.

Procedure time: 1-3 mins (1 mins for experienced practitioners)

Common indications

Common: postoperative analgesia for:

1. Pfannenstiel incision e.g. caeserian section, abdominal hysterectomy, ureteric reimplantation .

2. Inguinal hernia repair.

3. Orchidopexy.

4. Hydrocelectomy (need local infiltration of scrotum or separate pudendal block to cover scrotal incision).

Less common: primary anesthesia for the above proecedures.

Sedation: e.g. midazolam 2 mg + alfentanil 250-500 mcg or more commonly after GA.

Surface landmarks: mark out the anterior superior iliac spine.

Needle: 22G blunt needle (will facilitate observation of the needle tip in the correct plane by casuing tissue displacement)


1. High resolution (10-15 MHz) but narrow footprint linear array probe e.g. SonoSite hockey stick or alternatively standard linear probe

2. 22G blunt needle

3. 20 mL LA filled syringe.


1. Place a linear probe in the axial plane at the level of the anterior superior iliac spine. Visualisation of the abdominal muscle layers at this level is particularly subject to the US beam being directly perpendicular to the target structures. For this reason, the optimal position for probe placement is often above/cephalad of the anterior superior iliac spine orientated in a slightly caudad direction and often facing the contralateral foot. If a wide linear probe is used, it is often necessary to have the lateral part of the probe overhang the anterior superior iliac spine (Fig. 1).

 ultrasound guided ilioinguinal block

 Fig. 1. Ilioinguinal block (pediatric). Probe typically faces towards the contralateral foot, and often has to overhang the anterior superior iliac spine (ASIS) to achieve the correct orientation in relation to the target muscles.

2. Identification of the relevant muscles (Fig. 2) is from deep to superficial as in 50% of patients, the external oblique muscle will not be visible cephalad of the anterior superior iliac spine (in these patients only the muscle aponeurosis is present). 13 If only two muscles are visible, they most likely represent the internal oblique and transversus abdominis muscles. Occasionally, the (hypoechoic) nerves are visible between the internal oblque and transversus abdiminis muscles. If not visualised, simply inject LA between the respective muscles.

ultrasound guided ilioinguinal block sonography

Fig. 2. Ilioinguinal block sonographic image (pediatric). EO=external oblique muscle. IO=internal oblique muscle. TA=transversus abdominus muscle. ASIS=anterior superior iliac spine.

3. Using out of plane needle-probe orientation, a short bevel needle is advanced with a series of short/sharp pushes while observing for tissue displacement within the external and internal oblique muscles. Ideally the needle tip should be visualised prior to injection. One or more test injections of local anesthetic are administered until spread is observed between the internal oblique and transversus abdominis muscles.

4. The entire dose of local anesthetic may then be injected


Local anesthetic regimen: 15-20 mL ropivacaine 0.5-75% (paediatric dose: 0.1-0.2 mL/kg) 7, 13

Specific Complications

1. Bowel perforation. Exceedingly uncommon when the needle is kept superficial.

2. Femoral nerve block (quadriceps weaknesss). Uncommon in the absence of high LA volume.

Clinical PEARLS



Video 1. Ilioinguinal block.

Video 2. Ilioinguinal block sonography.


1.         Fisher QA, McComiskey CM, Hill JL, et al. Postoperative voiding interval and duration of analgesia following peripheral or caudal nerve blocks in children. Anesth Analg 1993;76:173-7.

2.         Hannallah RS, Broadman LM, Belman AB, et al. Comparison of caudal and ilioinguinal/iliohypogastric nerve blocks for control of post-orchiopexy pain in pediatric ambulatory surgery. Anesthesiology 1987;66:832-4.

3.         Splinter WM, Bass J, Komocar L. Regional anaesthesia for hernia repair in children: local vs caudal anaesthesia. Can J Anaesth 1995;42:197-200.

4.         Markham SJ, Tomlinson J, Hain WR. Ilioinguinal nerve block in children. A comparison with caudal block for intra and postoperative analgesia. Anaesthesia 1986;41:1098-103.

5.         Somri M, Gaitini LA, Vaida SJ, et al. Effect of ilioinguinal nerve block on the catecholamine plasma levels in orchidopexy: comparison with caudal epidural block. Paediatr Anaesth 2002;12:791-7.

6.         Findlow D, Aldridge LM, Doyle E. Comparison of caudal block using bupivacaine and ketamine with ilioinguinal nerve block for orchidopexy in children. Anaesthesia 1997;52:1110-3.

7.         Willschke H, Bosenberg A, Marhofer P, et al. Ultrasonographic-guided ilioinguinal/iliohypogastric nerve block in pediatric anesthesia: what is the optimal volume? Anesth Analg 2006;102:1680-4.

8.         Shivashanmugam T, Kundra P, Sudhakar S. Iliac compartment block following ilioinguinal iliohypogastric nerve block. Paediatr Anaesth 2006;16:1084-6.

9.         Frigon C, Mai R, Valois-Gomez T, et al. Bowel hematoma following an iliohypogastric-ilioinguinal nerve block. Paediatr Anaesth 2006;16:993-6.

10.       Johr M, Sossai R. Colonic puncture during ilioinguinal nerve block in a child. Anesth Analg 1999;88:1051-2.

11.       Vaisman J. Pelvic hematoma after an ilioinguinal nerve block for orchialgia. Anesth Analg 2001;92:1048-9.

12.       Amory C, Mariscal A, Guyot E, et al. Is ilioinguinal/iliohypogastric nerve block always totally safe in children? Paediatr Anaesth 2003;13:164-6.

13.       Willschke H, Marhofer P, Bosenberg A, et al. Ultrasonography for ilioinguinal/iliohypogastric nerve blocks in children. Br J Anaesth 2005;95:226-30.

14.       van Schoor AN, Boon JM, Bosenberg AT, et al. Anatomical considerations of the pediatric ilioinguinal/iliohypogastric nerve block. Paediatr Anaesth 2005;15:371-7.

15.       Sasaoka N, Kawaguchi M, Yoshitani K, et al. Evaluation of genitofemoral nerve block, in addition to ilioinguinal and iliohypogastric nerve block, during inguinal hernia repair in children. Br J Anaesth 2005;94:243-6.