Dear Editor,
Ilioinguinal nerve (IIN), iliohypogastric nerve (IHN), and genital branch of the genitofemoral nerve (GBN) are the three nerves encountered in the surgical field during open inguinal hernioplasty. Cadaveric studies suggest that it is possible to identify the IIN and IHN in almost all cases.1 However, the surgical literature does not support this finding, as identification rates are low for unexplained reasons. We need to analyze these reasons, as unspecified nerve injuries can cause post-operative in guinodynia. Additionally, the failure to recognize nerves indicates a possible inadequate surgical dissection.2 Based on current evidence, there appears a need to investigate the factors that affect nerve recognition.
Our study aimed to assess the rate of nerve identification and explore potential influencing factors. A cross-sectional study was conducted from June 2020 to May 2022 at a tertiary care teaching hospital at Odisha, India after obtaining due ethical clearance certificate from the institution and informed consent from all the study participants. Based on previous studies, the sample size was fixed at thirty-six.3,4 We included in this study all male patients with primary inguinal hernias above 18 years of age, having an American Society of Anaesthesiologists classification (ASA) grade of less than three. Patients who refused open surgery, those with recurrent or complicated inguinal hernias, and those operated on in the emergency operating theatre were excluded. In the initial cases, a consultant with over 12 years of experience performed the surgery. Subsequently, the cases were performed by residents under supervision. Our plan was to assess the impact of body mass index (BMI), height, type of anaesthesia, surgical experience, ASA grade, type of hernia, and hernia sac contents on nerve identification.
The participants had a mean ± standard deviation age of 48.14 ± 13.9 years, a height of 1.6 ± 0.1 m, a weight of 60.8 ± 9.9 kg, and a BMI of 23.44 ± 3.75 kg/m2. Among the cases, 66 % of the hernias were located on the right side (Table 1). The identification rates for the three nerves-IIN, IHN and GBN-were 86.1 %, 75 %, and 50 %, respectively. The identification of the IIN was not influenced by any factors except the content of the hernia sac (Table 2). Notably, the nerve was easily identified when the sac contained omentum. On the other hand, the identification of the IHN was affected by the patient's BMI, with easier identification observed in patients with a BMI ≤25 kg/m2 (Table 2).
Table 1.
Patient characteristics and important anatomical findings.
| Patient characteristics/anatomical findings | Mean (range)/proportiona | Box plot of distribution/bar diagramb |
|---|---|---|
| Age | 48 years (18–72 years) |  |
| Height | 1.61 m (1.45–1.76 m) |  |
| BMI | 23.4 kg/m2 (16.3–31.2 kg/m2) |  |
| Site of hernia | Right: 66.7 % Left: 33.3 % |
 |
| Relation of IIN with spermatic cord (n = 31) | Anterior: 90.3 % Posterior: 9.7 % |
 |
| Distance of IHN from deep ring (n = 27) | 2.6 cm (0.9–5.0 cm) |  |
Mean (range) for continuous variables and proportion for categorical variables.
Box plot of distribution for continuous variables and bar diagram for categorical variables.
Table 2.
Factors influencing the identification of inguinal nerves.
| Sl. No | Factors | Ilioinguinal nerve (p -value) | Iliohypogastric nerve (p -value) | Genital branch of Genito-femoral nerve (p -value) | |
|---|---|---|---|---|---|
| 1 | BMI | <25 kg/m2 (n = 26) | 0.511 | 0.03 | 0.137 |
| ≥25 kg/m2 (n = 10) | |||||
| 2 | Height | ≤160 cm (n = 17) | 0.537 | 0.18 | 0.32 |
| >160 cm (n = 19) | |||||
| 3 | Type of anesthesia | Local (n = 10) | 0.511 | 0.13 | 1.00 |
| Spinal anesthesia (n = 26) | |||||
| 4 | Operating surgeon | Faculty (n = 11) | 0.123 | 0.14 | 0.07 |
| Resident (n = 25) | |||||
| 5 | ASA grade | 1 (n = 30) | 0.131 | 0.60 | 0.37 |
| 2 (n = 6) | |||||
| 6 | Type of hernia | Direct/Pantaloon (n = 11) | 0.581 | 0.53 | 0.28 |
| Indirect (n = 25) | |||||
| 7 | Contents of the sac | Bowel (n = 21) | 0.042 | 0.33 | 0.31 |
| Omentum (n = 15) | |||||
We examined thirty-six patients and successfully identified the IIN in 86.1 %, the IHN in 75 %, and the GBN in 50 % of the cases. The ease of identification followed this order: IIN > IHN > GBN. This finding aligns closely with the results reported by Grossi et al, who observed similar identification rates of 86.6 % for both the IIN and the IHN.4 However, identifying the GBN, a thin nerve located posteriorly in the inguinal canal, proved to be particularly challenging. Reinpold et al managed to identify the GBN in only 40 % of the cases.5
The major course of the IHN within the inguinal canal lies between the external oblique and internal oblique muscles, positioned above and parallel to the spermatic cord. Visualizing this nerve necessitates tissue retraction, which can be obstructed in obese individuals. In contrast, the IIN is situated within the spermatic cord and centrally within the surgical field.3 The visualization of IIN does not require extensive retraction, making its identification less problematic in overweight individuals. Similar findings were reported by Cirocchi et al in a study involving 115 patients.6
The contents of the hernia sac can cause stretching and distortion of the spermatic cord. The presence of bowel, which contains gas, can result in more significant anatomical distortion compared to omentum. This particularly affects the recognition of nerves, especially the IIN, which is located within the spermatic cord. In our study, we failed to recognize the IIN in 23.8 % (5 out of 21) of cases when the bowel was present in the sac. On the other hand, we were able to identify the IIN in all cases where omentum was present. The presence of bowel influenced the course of the IIN, making its identification challenging.
We also investigated the potential impact of an individual's height on nerve recognition, as it can alter the length of the inguinal canal. To explore this, we divided participants into two groups: those with a height of ≤160 cm, considered below average.7 Furthermore, we examined the effect of anaesthesia on nerve recognition. It is possible that patients who underwent surgery under local anaesthesia might not allow proper retraction due to anxiety or discomfort. However, in our study, we observed no effect of height or type of anaesthesia on nerve recognition. We investigated the potential relationship between surgical experience and nerve recognition. In our study, 11 patients underwent surgery by faculty members, but nerve recognition in these cases was not significantly different from those operated on by residents.
Different types of hernias, such as direct hernias and indirect hernias, can impact the anatomy of the inguinal canal in distinct ways. Indirect hernias tend to stretch the spermatic cord, while direct hernias displace it. However, in our study, we did not observe a significant effect on nerve recognition based on the type of hernia. Additionally, we failed to find any evidence suggesting that the preoperative performance status of the patients influenced nerve recognition. Patient consent was obtained.
There are few limitations to this study. Firstly, the sample size was determined based on the analysis of nerve prevalence during surgery, which means the study may be underpowered to assess the effect of various factors on nerve identification. Additionally, the surgeries were performed by surgeons with varying levels of experience.
Our study demonstrates that the identification of IIN and IHN is feasible in the majority of cases, while the GBN poses challenges due to its thin nature. Significant factors influencing the identification of IIN and IHN include the BMI and the content of the hernia sac.
Patients/ Guardians/ Participants consent
Patients informed consent was obtained.
Ethical clearance
Not Applicable.
Source of support
Nil.
Disclosure of competing interest
The authors have none to declare.
Acknowledgements
We express our sincere thanks to Dr Satya Prakash, Department of Transfusion Medicine, AIIMS Bhubaneswar for reviewing the statistics of this article.
References
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