The Accuracy of Silk Glove Sign Compared with Inguinal Bulge in the Diagnosis of Indirect Inguinal Hernia in Children

Introduction

Inguinal hernia repair is one of the most common operations performed in pediatric and adult population.^1–4 Its incidence varies from 0.8% to 5% in term patients and rises to 30% in preterms. ¹ A clinical history and physical exploration of inguinal bulge remains the main diagnostic tool. When inguinal bulge is not appreciated, the diagnosis is based on indirect signs, being then, less precise. ⁵

The silk glove sign (SGS) is a physical examination for detecting indirect inguinal hernias. ⁶ The surgeon places one finger to the lateral side of pubic tubercle and the hernial sac can be detected when it gives a sensation of rubbing two pieces of silk together.^6,7 There are only a few reports in the literature comparing SGS with intraoperative findings. The aim of our study was to compare physical examination findings with intraoperative results and to evaluate the accuracy of inguinal bulge and SGS in the diagnosis of indirect inguinal hernias.

Materials and Methods

A retrospective study of 512 pediatric patients who underwent laparoscopic inguinal hernia repair from January 2002 to November 2015 in a tertiary center was performed. Indications for laparoscopic repair were bilateral inguinal hernia, unilateral inguinal hernia associated with umbilical hernia, doubtful diagnosis (direct or femoral hernia), and recurrence after either laparoscopic or open repair. Hospital records were reviewed for preoperative and intraoperative parameters. A total of 1024 inguinal canals were analyzed. Inguinal canals were divided into two groups according on preoperative physical exploration: in group 1 where those with inguinal bulge and in group 2 where those with SGS positive. Exclusion criteria were unknown and doubtful physical exploration. The ethics committee of our center approved the study.

Each patient was examined by an attending or a resident supervised by an attending. SGS was defined as the sensation of rubbing two pieces of silk together when the physician palpated the processus vaginalis over the pubic tubercle. Inguinal bulge was defined as a visible inguinal lump during the Valsalva maneuver. We have considered both signs mutually exclusive. During laparoscopic procedure, the internal inguinal ring was evaluated bilaterally. Intraoperative diagnosis of indirect inguinal hernia was the presence of an open internal inguinal ring, in which a dissector could be introduced deeply. All the hernias were laparoscopically repaired using a purse-string suture.

SAS^® 9.3 software (SAS Institute Inc., Cary, NC) was used for statistical analyses. Nonparametric test was used to compare the groups due to the small samples. Continuous variables were compared between both groups using Wilcoxon rank-sum test and categorical variables were compared using Pearson chi-square test. A P value of <.05 defined statistical significance. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated.

Results

Preoperative physical examination of the inguinal canals was unknown in 119 (11.6%) cases, inguinal bulge in 379 (37.0%) cases, SGS in 196 (19.1%) cases, normal in 266 (25.9%) cases, and doubtful in 64 (6.4%) cases. Therefore, the main studied population (group 1 and group 2) consisted of 575 cases. The majority of the patient demographics parameters were statistically different in both groups, as it is observed in Table 1. Gender distribution was 257 boys (67.8%) and 122 girls (32.2%) in group 1, and 118 boys (60.2%) and 78 girls (39.8%) in group 2 (P = .08). Episodes of incarceration were significantly more common in group 1 (16.4%) than in group 2 (0.5%) (P < .01).

A greater proportion of patients in group 1 were intraoperatively reported to have an inguinal hernia (98.7%) as compared with group 2 (86.7%) (P < .01). In group 1, 5 cases with an inguinal bulge had no inguinal hernia and 108 cases without inguinal bulge had an inguinal hernia, resulting in a sensitivity of 78%, a specificity of 97%, a positive predictive value of 98%, and a negative predictive value of 60%. Contingency table of group 1 is showed in Table 2. In group 2, 26 cases with SGS positive had no inguinal hernia and 108 without SGS positive had inguinal hernia, resulting in a sensitivity of 61%, a specificity of 86%, a positive predictive value of 86%, and a negative predictive value of 60% (Table 3).

Discussion

Despite indirect inguinal hernia being one of the most common surgical conditions in children, there is an endless controversy regarding diagnosis and surgical treatment. Given the risk of incarceration, it is customarily recommended that all patients with an inguinal hernia undergo surgical repair shortly after detection. ¹ Episodes of incarceration in untreated hernias in pediatric patients occur between 6% and 18%, but this percentage increases up to 30% in infancy. ¹ In addition, the rate of complications in incarcerated hernias is higher, reported between 4.5% and 33%. ²

Although there are numerous articles regarding data about the incidence of patent processus vaginalis (PPV), there is no a unanimous opinion about their optimal treatment. ³ The incidence of PPV has been reported to be up to 66% or even higher in the smaller infants. ¹ In children undergoing unilateral inguinal hernia repair, there is a possibility that a contralateral PPV will develop into clinical hernia (metachronous hernia), requiring a new operation and a second anesthesia.^1–3 The actual incidence of developing a metachronous hernia is ∼5%–20%.^1,2 However, this can only be suggested due to the lack of studies in the adult population and lifetime follow-up. ³ Van Veen et al. reported that the chance of developing an inguinal hernia in adult patients diagnosed with PPV is four times higher as compared with patients without PPV. ⁴ In addition, they did not find a correlation between age and prevalence of PPV as it occurs in children. ⁴

Although routine open contralateral exploration is not recommended because of the risks associated with a new incision and manipulation of the spermatic cord in males, laparoscopic exploration and repair is still controversial.^2,4 Clinical diagnosis of inguinal hernias is not as simple as it seems. They usually present as intermittent bulge in the inguinal region or in the scrotum that it is usually seen during crying, bathing, or diaper change.^1,2 However, there is not always an obvious inguinal bulge during physical examination. The SGS is a physical finding that can help in the diagnosis of indirect inguinal hernia. It consists of detecting thickening on palpating PPV over the pubic tubercle.^5–7 Although SGS as indicator of inguinal hernia is well documented, there are only a few studies that compare preoperative SGS with intraoperative findings.^5–7 Luo and Chao have found a sensitivity of 93.1% and a specificity of 97.3%, and they have concluded that SGS was reliable in minimizing unnecessary surgical explorations. ⁵ Malakounides and Jones have observed poor sensitivity (37%–75%) and specificity (80%–87%) with high interobserver variability. ⁶ They recommend a laparoscopic evaluation of the presence of a contralateral PPV. ⁶ Taisab and Laohapensang have compared diagnostic accuracy of SGS and ultrasound findings with intraoperative diagnosis. ⁷ They have observed that ultrasound findings had a higher specificity and sensitivity. ⁷ Since ultrasound findings depend highly on the operator's experience, its accuracy varies among studies. A recent meta-analysis showed a greater variability in the sensitivity and specificity of ultrasound. ⁸

In our study, we have observed a low sensitivity, an acceptable specificity, and a high positive predictive value in both groups, regardless of clinical findings. Consequently, we still maintain our indications for laparoscopic inguinal hernia repair. If a patient has a bilateral inguinal bulge or SGS or these findings are associated with umbilical hernia, the patient will undergo laparoscopic exploration and inguinal hernia repair where appropriate. We agree with other authors that foremost among the advantages of laparoscopic technique is the identification and treatment of a contralateral PPV. ¹ Given the possibility of a contralateral PPV, it has been demonstrated that the majority of the children's parents prefer laparoscopic exploration and unilateral or bilateral repair according to the intraoperative findings.^9,10 In patients with preoperative unilateral inguinal hernia who underwent laparoscopic procedure, Esposito et al. have identified and treated a contralateral PPV in the 44.9% of patients. ¹⁰ However, despite a growing trend toward laparoscopic unilateral inguinal hernia repair, open surgery is still the preferred way to treat unilateral hernias.