Prediction of contralateral inguinal hernias in children: a prospective study of 357 unilateral inguinal hernias

The incidence of contralateral inguinal hernias in children after unilateral hernia repair is 5.8–11.6 % [1, 2]. It is debatable whether contralateral exploration is necessary in children with unilateral inguinal hernia in conventional open herniorrhaphy. Although, inguinal hernia repair is among the most common procedures performed by pediatric surgeons, surgical management of the contralateral groin remains controversial. Exploration of the asymptomatic side is designed to detect a patent processus vaginalis or non-evident clinical hernia. The goals of identifying these two entities are to avoid a second anesthesia, minimize parental and patient inconvenience, avoid the chance of incarceration, and reduce costs [3]. Potential disadvantages to exploration of the asymptomatic side include injury to the contents of the spermatic cord, wound infection, increased pain, increased cost, and prolongation of the operation [3]. Studies of methods to predict contralateral inguinal hernia could be helpful to avoid negative contralateral exploration. For this reason, pre-operative evaluation of the contralateral inguinal hernia is important in patients with unilateral hernia.

In our previous study [4], we retrospectively established a pre-operative risk scoring system for 662 patients with unilateral inguinal hernia to predict the incidence of contralateral hernia during 5 years (Fig. 1). The aim of the current study was to prospectively determine the incidence of contralateral inguinal hernia, risk factors, and the usefulness of our pre-operative risk scoring system.

A total of 372 consecutive patients were eligible for participation in the trial, of which 357 (96.0 %) patients were enrolled. Fifteen excluded patients were lost to follow-up. Surgery was performed in all cases at the Pediatric Surgery Department, Nihon University Hospital. No patients from the study had complications during surgery or follow-up or recurrence of the inguinal hernia. There was no history of trauma or urinary tract infection, and none of the patients had systemic disorders or chronic disease.

We performed 357 unilateral inguinal hernias and all were repairs of indirect hernias. The distribution per group is shown in Table 1. The gender distribution was 213 (59.7 %) males and 144 (40.3 %) females. The median age at the time of the initial operation was 41 months (range 28 days–13 years). Seventy-two (20.2 %) were low birth weight infants; 192 (53.8 %) had a hernia on the right side and 165 (46.2 %) on the left; and 23 (6.4 %) developed a contralateral inguinal hernia. Although the contralateral hernia developed significantly and more frequently in patients with left-sided hernia (p = 0.035), there was no significant difference between the groups regarding other factors such as gender, age, and birth weight using univariate analysis (Table 1).

The incidence of contralateral hernia by gender and initial operation side is shown in Table 2. The most frequent rate of occurrence of the contralateral hernia was 10.0 % in the girls whose initial operation side was the left. These results approximated our previous retrospective study (data not shown).

We verified the accuracy of our pre-operative risk score and initial operation side for the prediction of contralateral inguinal hernia in children.

Inguinal hernia repair is the most common operation in pediatric surgical practice with most pediatric surgeons performing hundreds of hernia repairs each year. The incidence of contralateral occurrence of pediatric inguinal hernia after repair of unilateral inguinal hernia is 5.8–11.6 % [1, 2]. Although the risk of pediatric general anesthesia and the complication rate of inguinal hernia repairs are low, second operations should be avoided by identifying the patients who are at high risk for contralateral hernia before the initial surgery.

There is some controversy about the management of the contralateral groin in patients with unilateral hernia. Physical examination findings (such as “silk sign”), herniography [5], the Goldstein test using pneumoperitoneum [6, 7], contralateral exploration [8, 9], laparoscopy [10‐13], and ultrasonography [14] are reported methods for predicting contralateral occurrence. Physical examination signs such as the “silk sign” do not reliably identify a contralateral hernia because detection varies according to the subjective palpation of the surgeons. Herniography was designed to detect the presence of a contralateral patent processus vaginalis (CPPV), and although this technique is accurate, the main disadvantages are pain, gonadal irradiation, and complications from the injection. The Goldstein test is a method to insufflate air into the contralateral groin using a catheter placed in the hernia sac. This technique is difficult in preterm infants and newborns because of a friable hernia sac. Contralateral exploration is a method to diagnose the presence of a CPPV in patients who undergo repair of unilateral inguinal hernia. This technique may lead to spermatic cord injury, testicular atrophy, and wound infection. Even if contralateral inguinal exploration was technically easy and safe, hernia repair on the other side in all patients with unilateral hernia who have positive findings on exploration is an overtreatment. Contralateral laparoscopy can accurately diagnose the presence of a CPPV, but the relationship between the presence of a CPPV and the subsequent development of a contralateral inguinal hernia remains unknown. This is why routine contralateral inguinal exploration using laparoscopy has not been widely accepted [15, 16]. Ultrasonography is a safe and non-invasive method to detect the presence of CPPV. The main advantage of this technique is that it can diagnose the hernia before the initial operation. Hata [14] reported that CPPV was detected correctly using ultrasound in 74 of 348 (21.3 %) patients. However, the incidence of contralateral occurrence of pediatric inguinal hernia after hernia repair [1, 2] is lower than the incidence of CPPV confirmed by ultrasonography [14] and laparoscopy [8‐13]. This finding indicates that patency of the processus vaginalis alone cannot be considered a sufficient condition for inguinal hernia development.

Based on our previous study [4], we retrospectively established a pre-operative risk scoring system to predict the incidence of contralateral hernia in 662 patients with unilateral hernia. In the current study, we prospectively analyzed 357 patients with unilateral hernia for the risk of developing a contralateral hernia using multivariate analysis and the pre-operative risk score. We found that an initial presentation with a left-sided hernia was associated with a 5.5-fold increased risk for developing a contralateral hernia. The odds ratio for left-sided hernia was high and similar to our previous report using multivariate methods [17]. We also confirmed the utility of our pre-operative risk scoring system for the prediction of the development of a contralateral hernia, especially over 4.5 points patients.

In conclusion, in this prospective study using multivariate analysis, we demonstrated the utility of our pre-operative risk score and initial operation side for the prediction of the development of a contralateral inguinal hernia in children. We believe that contralateral exploration based on our pre-operative risk scoring system was reliable in minimizing unnecessary surgical exploration. A wait-and-see policy is recommended in patients at low risk for contralateral hernia development, while those at high risk for contralateral hernia would benefit from laparoscopic exploration of the contralateral side. However, our pre-operative risk score alone is insufficient to predict the development of a contralateral hernia, and other methods with higher sensitivity and specificity are still needed.