Improved Perioperative Analgesia with Ultrasound- Guided Ilioinguinal/iliohypogastric Nerve or Transversus Abdominis Plane Block for Open Inguinal Surgery: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Research Article

Phys Med Rehabil Int. 2015;2(6): 1055.

Improved Perioperative Analgesia with Ultrasound- Guided Ilioinguinal/iliohypogastric Nerve or Transversus Abdominis Plane Block for Open Inguinal Surgery: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Yuexiang Wang1,2, Tao Wu³, Marisa J Terry³, Jason S Eldrige¹, Qiang Tong1,3, Patricia J Erwin4, Zhen Wang5 and Wenchun Qu1,3*

1Department of Anesthesiology Pain Division, Mayo Clinic, Rochester, USA

2Department of Ultrasound Medicine, Chinese PLA General Hospital, Beijing, China

3Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, USA

4Department of Library-Public Services, Mayo Clinic, Rochester, USA

5Center for the Science of Healthcare Delivery, Mayo Clinic, Rochester, USA

*Corresponding author: Wenchun Qu, Department of Physical Medicine and Rehabilitation, Department of Anesthesiology Pain Division, Mayo Clinic, Rochester, 55905, USA

Received: May 22, 2015; Accepted: July 23, 2015; Published: July 27, 2015


Ilioinguinal/iliohypogastric (II/IH) nerve and transversus abdominis plane (TAP) blocks are both effective perioperative analgesic techniques for open inguinal surgery. Ultrasound-guided II/IH nerve and TAP blocks have been increasingly utilized in patients for perioperative analgesia. Yet the use of ultrasound has not been fully evaluated. We conducted this meta-analysis to evaluate the clinical efficacy of ultrasound-guided II/IH nerve or TAP blocks for perioperative analgesia in patients undergoing open inguinal surgery. A systematic search of seven databases was conducted from database inception to March 5, 2015. Randomized controlled trials (RCTs) comparing the clinical efficacy of either ultrasound-guided or landmark-based techniques to perform II/IH nerve and TAP blocks for perioperative analgesia in patients with open inguinal surgery were included. Two reviewers independently (and in duplicate) screened abstracts and full texts. We constructed random effects models to pool standardized mean difference (SMD) for continuous outcomes and odds ratio (OR) for dichotomized outcomes. Heterogeneity between studies was estimated by I2statistic. One hundred thirty-nine articles were identified and among them 4 articles were eligible for the final analysis. Ultrasound-guided II/IH nerve or TAP blocks were associated with reduced use of intraoperative additional analgesia with OR=0.21 (95% CI: 0.09 to 0.49; p<0.001; I2= 0.00%) and significant reduction of pain scores during day-stay with SMD=-0.96 (95% CI: -1.68 to -0.24; p<0.001; I2=88.3%). The use of rescue drug was also significantly lower in the ultrasound-guided group (OR=0.16; 95% CI: 0.06, 0.40; p<0.001, I2=10.2%). In conclusion, the use of ultrasound-guidance to perform an II/IH nerve or a TAP block was associated with improved perioperative analgesia in patients following open inguinal surgery compared to landmark-based methods.

Keywords: Ultrasound; Ilioinguinal/iliohypogastric nerve; Inguinal surgery


II/IH: Ilioinguinal/Iliohypogastric; TAP: Transversus Abdominis Plane; RCT: Randomized Controlled Trials; SMD: Standard Mean Difference; OR: Odds Ratio.


Open inguinal surgery can lead to high levels of intra- and post-operative pain. Currently available perioperative pain management options include oral or intravenous analgesics, surgical wound infiltration, and single-shot caudal blocks. However, these treatments may yield suboptimal pain control or may be limited by the significant risk of side effects. Of the commonly used oral analgesics, acetaminophen has only mild analgesic properties and has a prolonged time to onset [1, 2]. Opioid medications are associated with somnolence, nausea, vomiting, and respiratory depression [1]. The potential risks of caudal blocks include subcutaneous infiltration, blood vessel puncture, and dural penetration [3, 4]. Recently, ilioinguinal/iliohypogastric (II/IH) nerve or transversus abdominis plane (TAP) blocks have attracted interest as viable alternatives [5- 11] to provide effective perioperative analgesia for open inguinal surgery. Importantly, it may provide similar duration of analgesia as a caudal block, with a smaller dosage of local anesthetic agent, at 0.3 ml/kg of 0.25% bupivacaine in II/IH block compared to 1 ml/kg used in caudal block [7,12].

There are two main techniques for II/IH or TAP blocks: the landmark-based method or the use of ultrasound guidance. Traditional landmark-based II/IH block using a fascial "click" technique has a low accuracy rate and is associated with increased procedural risks. It is difficult to identify the correct fascial plane, which may lead to the need for multiple attempts [9, 10, 11]. A failure rate of 28-45% has been reported, even in experienced hands [13,14]. Weintraud et al [14] reported a mere 14% accuracy rate when local anesthetic was deposited using a landmark-based approach and subsequently imaged under ultrasound to document the location of the fluid collection. No optimal injection site along the course of II/IH nerve have been identified to improve the accuracy rate largely due to the fact that none of the sites studied has an anatomical feature that would make the ‘clicking’ prominent enough to be reproducible [13, 15-18]. In addition, landmark-based techniques are associated with substantial risk of colonic or small bowel punctures, pelvic hematoma [19-21], and femoral nerve palsy [22-24].

Ultrasound guidance in regional anesthesia has gained popularity in recent years [25, 26-28]. It has emerged as an excellent modality to visualize the TAP, II/IH nerves, vessels, and needle, which may be beneficial in reducing the risk of intraneural, intravascular, or intraperitoneal injections. In addition, a smaller dosage of local anesthetic may be possible because the needle placement can be confirmed, which negates any additional volume used to offset for inaccurate needle placement [16, 29-33]. The disadvantages of an ultrasound guided procedure are the required special equipment, training, and increased cost. The cost-benefit justification requires assessment of efficacy with ultrasound guidance in comparison with landmark-based approach. Multiple randomized controlled trials have been conducted, but often with small sample size, heterogeneous designs, and conflicting outcomes. Therefore, we conducted this systematic review and meta-analysis to summarize the current evidence and evaluate the clinical efficacy of ultrasound-guided II/ IH or TAP block for perioperative analgesia in pediatric and adult patients undergoing inguinal surgery.


The study protocol was finalized in advance of any data collection, which defined objectives, search strategy, inclusion/exclusion criteria, data extraction, outcomes of interest, and analytical approaches. The reporting of this systematic review complies with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement [34,35].

Search strategy and study selection

Comprehensive searches were performed on PubMed, Ovid MEDLINE, Ovid EMBASE, Ovid Cochrane CENTRAL, Web of Science, and Scopus from database inception through on March 8, 2015. Each concept used a combination of controlled vocabulary (MeSH and EMTREE) combined with text words for each database which uses subject heading (PubMed, MEDLINE, EMBASE, CENTRAL). Web of Science and Scopus depend primarily on text words alone. The subject headings included inguinal canal, hernia, and inguinal, inguinal hernia and text words: inguinal, ilioinguinal or iliohypogastric. In the same fashion, the concept of pain and ultrasound guidance included nerve block, pain, postoperative, as well as text words for ultrasound: echogram*, ultrasound, ultrasono*. Each search was imported into an EndNote (Thomson Reuters Research Soft), a bibliographic database manager, and duplicates removed.

Inclusion and exclusion criteria

We included randomized controlled trials (RCTs) comparing the clinical efficacy of II/IH nerve or TAP block using ultrasound guidance vs. landmark-based technique for perioperative analgesia in patients following open inguinal surgery. Case series and case reports were excluded. Articles focusing on the therapeutic effect of ultrasound-guided II/IH nerve block for chronic inguinal pain were excluded. Articles focusing on the comparison of ultrasound-guided II/IH nerve or TAP block and wound infiltration were also excluded.

Data extraction and quality assessment

Two reviewers, working independently and in duplicate, (Y.W. and M.T.) reviewed titles and abstracts and then full texts in order to exclude irrelevant studies. All conflicts were discussed and resolved with a third author (W.Q.). The same two reviewers extracted study details from the full text studies using a standardized pilot-tested form. The following data were extracted: the author, year of publication, study location, sample size, patient characteristics (gender, age), general anesthesia, regional anesthesia, timing of regional anesthesia, the surgery performed, and outcome measures including the number of patients receiving additional analgesia during surgery and pain scores of patients during day-stay. The reference sections of all articles were used to identify additional relevant articles.

Quality assessment

We used the Cochrane Risk of bias tool to assess the methodological quality of the included RCTs in terms of sequence generation, allocation concealment, blinding, incomplete outcome data, selective outcome reporting, and other sources of bias [36].

Statistical analysis

For the continuous outcomes (pain scores), we combined standardized mean difference (SMD) from the included studies using the Der Simonian and Laird random-effect models [37]. We also calculated odds ratio (OR) for dichotomized outcomes and pooled OR using the Der Simonian and Laird random-effect models.

We used the I2 statistic to measure the heterogeneity across the included studies, in which I2>50% suggests high heterogeneity [38]. Although we planned to assess publication bias by visual inspection of funnel plots and conducting the Egger regression asymmetry test, we were unable to conduct these tests due to the limited number of the included studies [39,40]. All statistical analyses were conducted using STATA version 12.1 (Stata Corp LP, College Station, Texas).


Study characteristics

We identified 139 articles, of which four RCTs [16, 41-43] conducted between 2005 and 2014 were eligible for this review (Figure 1). Characteristics of the enrolled studies are described in Table 1. Patients of all ages were included. All patients underwent open surgeries including inguinal hernia repair, orchidopexy, hydrocelectomy or hydrocele repair. All patients received general anesthesia that was maintained by Halothane or Sevoflurane in nitrous oxide and oxygen. All patients were randomized into one of the two technique groups: ultrasound guided group and landmarkbased group. All ultrasound guided procedures were performed with a high frequency linear probe.The procedures of the control group were performed with landmark-based technique. All II/IH nerve or TAP blocks in both groups were performed before surgery.