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Table of Contents
ORIGINAL ARTICLE
Year : 2019  |  Volume : 30  |  Issue : 1  |  Page : 24-29

Second repair of pediatric inguinal hernia: A longitudinal cohort study


1 Division of Urology, Department of Surgery, Taipei Tzu Chi Hospital, The Buddhist Tzu Chi MedicalFoundation, New Taipei; School of Medicine, Buddhist Tzu Chi University, Hualien, Taiwan
2 Institute of Epidemiology and Preventive Medicine, National Taiwan University, Taipei, Taiwan
3 School of Medicine, Buddhist Tzu Chi University, Hualien; Division of Pediatric Surgery, Department of Surgery, Taipei Tzu Chi Hospital, The Buddhist Tzu Chi Medical Foundation, New Taipei, Taiwan

Date of Web Publication2-Jan-2019

Correspondence Address:
Ke-Chi Chen
Division of Pediatric Surgery, Department of Surgery, Taipei Tzu Chi Hospital, The Buddhist Tzu Chi Medical Foundation, New Taipei
Taiwan
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/UROS.UROS_26_18

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  Abstract 


Background: The objective of this nationwide observational study was to report the rate and risk factors for the second repair after pediatric inguinal herniorrhaphy. Materials and Methods: Children born from 1998 to 2005 were chosen from a cohort of 1,000,000 cases, which were randomly selected from an insured population of 23 million people in Taiwan (Longitudinal Health Insurance Database 2005). We identified all hernia repairs in the period of 1998–2012 for the sample population and then used a Cox proportional hazards regression model to analyze the risk factors for the second repair after pediatric inguinal herniorrhaphy. Results: The total sample population comprised 79,820 children, with a male-to-female ratio of 4.27:1. During a mean observation period of 11.4 ± 2.2 years, 3339 (4.18%) of the children in the sample population received primary inguinal hernia repair. Of the 251 children (7.52%) who underwent a second repair, 220 were boys (8.13%) and 31 were girls (4.9%); 244 (8.62%) underwent primary unilateral hernia repair, and 7 (1.38%) underwent primary bilateral hernia repair. Considering that bilateral hernia involves unilateral hernia on two sides, the expected recurrence rate after primary unilateral hernia repair was calculated as 0.69%. The calculated rates for late occurrence of contralateral hernia after primary unilateral hernia repair were 11.04%, 7.73%, and 3.28% for children aged 0–1, 1–4, and >4 years, respectively. Significant risk factors for second hernia repair were age at first primary hernia repair and unilateral hernia (P < 0.001). Gender and prematurity were not risk factors for second hernia repair. Conclusions: The second repair rate after primary unilateral or bilateral hernia repair was 7.52%. The only risk factor that predicted the second repair was age of <4 years at the time of operation. The expected recurrence rate after any hernia was estimated as 0.69%.

Keywords: Children, contralateral occurrence, inguinal hernia, recurrence, second repair


How to cite this article:
Chen YS, Yang SS, Chen JY, Chang SJ, Chen KC. Second repair of pediatric inguinal hernia: A longitudinal cohort study. Urol Sci 2019;30:24-9

How to cite this URL:
Chen YS, Yang SS, Chen JY, Chang SJ, Chen KC. Second repair of pediatric inguinal hernia: A longitudinal cohort study. Urol Sci [serial online] 2019 [cited 2019 May 19];30:24-9. Available from: http://www.e-urol-sci.com/text.asp?2019/30/1/24/249263


  Introduction Top


The reported incidence of hernia is 0.8%–4.4% in full-term infants and up to 30% in preterm infants.[1],[2],[3] Although inguinal hernia is the most common surgical disease in children,[4] few cohort studies have focused on the prevalence or incidence of its contralateral occurrence or of hernia recurrence at the original site of operation. In most relevant studies, hernia recurrence or contralateral occurrence rates have been investigated using estimations based on reports from surgeons,[3] medical records,[5] or student health surveys.[6] A longitudinal cohort study is more suitable than the aforementioned methods for evaluating the second repair rate of pediatric inguinal hernia. In addition, the use of a nationwide study cohort may avoid the biases that affect single-institution studies and provide more accurate epidemiologic data on the second repair for recurrence after inguinal hernia repair.

The National Health Insurance (NHI) program covers more than 98% of Taiwan's total population of 23 million people. All patients' medical records are stored in the NHI Research Database (NHIRD), maintained by the Taiwanese Department of Health's National Health Research Institutes. The NHIRD is one of the largest insurance databases in the world and provides valuable information for epidemiological and medical research. Data from this database were used to conduct the present longitudinal cohort study of the second repair for recurrence and contralateral occurrence of hernia after primary inguinal hernia repair in children.


  Materials and Methods Top


Data source

We selected a subset of the Taiwan NHIRD known as the Longitudinal Health Insurance Database 2005 (LHID2005), which is a sample of 1 million people randomly drawn from the 23 million individuals in the Taiwan NHI registry of beneficiaries as of 2005 (i.e., individuals enrolled for all or any part of 2005). The LHID2005 contains all outpatient and inpatient medical claims from 1998 through 2012 for the sample individuals. The gender distribution between the patients in the LHID2005 and those comprising the total NHIRD registry does not differ significantly (χ2 = 0.007, df = 1, P = 0.941).

Study sample

Children with the International Classification of Diseases, Ninth Revision, (ICD-9) code 550 and surgery code 75606B, 75607C, 75610B, 75613C, or 88029C were regarded as having received inguinal hernia repair. We selected all patients born from 1998 to 2005 from the LHID2005, and from this group, we identified those who had undergone surgical procedures for hernia in the 1998–2012 claim records [Figure 1]. This study was approved by our institutional review board (project number: 04-W07-082). Variables such as gender, age at first hernia surgery, history of prematurity (gestational age <38 weeks), unilateral or bilateral repairs, outpatient or inpatient surgery, and specialty of the surgeons were analyzed. We defined primary repair as repair for the first hernia, including unilateral and bilateral hernia, and second repair as surgery for recurrence after primary repair or subsequent repair for late occurrence of contralateral hernia.
Figure 1: Flow diagram of the study cohort selection

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In the NHIRD, not all cases of recurrent hernia were comprehensively coded. The data did not indicate whether patients with unilateral hernia receiving second repair had presented with recurrence or contralateral occurrence of hernia. However, a case was inferred as recurrent hernia if the patient received second repair after a claim for bilateral hernia repair. Thus, the second repair rate was considered equal to recurrence rate in the group of patients who received bilateral primary repair. In addition, bilateral hernia repair was considered as comprising two sites of hernia repairs. Accordingly, the recurrence rate after primary bilateral hernia repair was halved to represent the expected recurrence rate for each site of primary repair.

We also evaluated prematurity, cryptorchidism, and congenital defects in histories of the studied children. Premature children were defined as those with a gestation age of <38 weeks with ICD-9 codes of 765.11, 765.12, 765.13, 765.14, 765.15, 765.16, 765.17, 765.18, or 765.19. Undescended testis was defined according to the ICD-9 Clinical Modification (ICD-9-CM) code 752.51. Concomitant birth defects were identified according to the ICD-9-CM codes 740–759. These factors were considered in the analysis of all patients.

Statistical analysis

In general, the continuous data were expressed as mean values with standard deviations, and the categorical data were expressed as numbers and percentages by group. A Cox proportional hazards regression model was used to calculate the risk of second inguinal hernia repair. Records with missing or unknown values for any of the variables of interest were excluded from the analyses. All statistical tests were two sided, and the level of significance was set at 0.05. The results were reported using P values or 95% confidence intervals. All statistical analyses were performed using the SAS statistical package version 9.3 for Window (SAS Institute, Cary, NC).


  Results Top


The study cohort comprised 79,820 children aged 0–15 years. [Table 1] lists the incidences of primary inguinal hernia repair according to the various ages and concomitant prematurity, cryptorchidism, and congenital birth defects of the included children. In total, 3339 children (4.18%) received primary inguinal hernia repair during the observation period of 11.2 ± 2.4 years. The male-to-female ratio of the study sample was 4.27:1, and 2830 unilateral repairs and 509 bilateral repairs were reported. Pediatric surgeons performed 1881 of the hernia repairs; urologists performed 575; other surgeons performed 875; and other specialists performed 8. Of the patients who underwent hernia repairs, 1727 received inpatient care and 1612 received outpatient care. Regarding the term of pregnancy, 191 children were born preterm and 3148 were born at full term.
Table 1: Demographic characteristics of patients who received primary and second inguinal hernia repair

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The study sample included 251 children (7.52%) who underwent the second repair, comprising 220 boys (8.13%) and 31 girls (4.9%). Of these children, 244 (8.62%) received primary repair for unilateral hernia and 7 (1.38%) received primary repair for bilateral hernia. Most second repairs were performed within 2 years of the first repair [Figure 2]. Because one bilateral hernia repair involves two unilateral hernia repairs, the expected recurrence rate of hernia based on sites of hernia was calculated as 0.69%. Regarding the primary repair for unilateral hernia, the rate of contralateral occurrence of hernia was estimated as the second repair rate minus the expected recurrence rate. Thus, the calculated rates of late occurrence of contralateral hernia after primary unilateral hernia repair were 11.04%, 7.73%, and 3.28% for children aged 0–1, 1–4, and >4 years, respectively.
Figure 2: Recurrence-free survival curves for primary unilateral and bilateral hernia repair (red line: bilateral, blue line: unilateral)

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[Table 2] summarizes the risk factors of the second repair after primary hernia repair. The risk for second hernia repair was high in the group of 1–4-year-old patients and highest in the 0–1-year-old patient group (P < 0.0001). The rate of the second repair was higher in the unilateral hernia than bilateral hernia group (8.62% vs. 1.38%, P < 0.001). The factors of inpatient versus outpatient, preterm versus full term, with versus without cryptorchidism, and with versus without congenital birth defect were not predictive of a second operation. Univariate analysis indicated that higher rates of the second repair were associated with surgeon specialists compared with other clinical professionals and with girls rather than boys. However, in the multivariate analysis, no significant differences for either the specialist or gender variables were identified [Figure 3].
Table 2: Risk factors for second hernia repair

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Figure 3: Forest plot illustrating the results from the multivariate Cox proportional hazards model for second hernia repair in a cohort of 3339 children whose data were accessed from the National Health Insurance Research Database

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  Discussion Top


With a mean follow-up of 11.4 years among the studied patients seen in hospitals nationwide in Taiwan, the rate of all second hernia repairs was 7.52%. In the bilateral group, second hernia repair rate was calculated as equal to the recurrence rate, at 1.38%. Each bilateral hernia repair was considered as comprising two sites of hernia repair. The expected recurrence rate of primary unilateral hernia repair was 0.69%. This low expected recurrence rate of inguinal hernia may reflect the advanced level of surgical care in Taiwan. Studies of other populations have indicated that the recurrence rate of pediatric inguinal hernia repair varies from 0% to 3.8%.[3],[7],[8],[9] Data in these studies were limited to single institutions or short observation periods. These data may have lacked accurate follow-up if patients underwent second surgical procedures at different hospitals than those where they received initial procedures. Ein et al. reported a 1.2% recurrence in 6361 cases of primary hernia repair,[3] and Erdoğan et al. calculated a 0.4% recurrence rate for 3773 cases of primary hernia repair.[9] These two studies involved large case numbers; however, the data were sourced from single institutions, which represents a study limitation, even if the institutions were tertiary centers. Bisgaard et al. conducted a nationwide observation of 2476 children who underwent primary hernia repair and reported a reoperation rate of 0.7% within a mean follow-up of 2 years.[10] The present study determined that most hernia recurrence was reported within 2 years of the initial operation [Figure 2]; thus, this finding agreed with the results of Bisgaard et al.'s study. In addition, the rate of primary hernia repair determined in the present study (4.18%) agreed with Pan et al.' s (2013) finding of 4.20%, which was determined using a different dataset from the same data bank.[11]

According to the results of the present study, the risk factors for the second repair were age of <4 years at the time of operation and unilateral hernia repair. The low recurrence rate for bilateral hernia suggested that the recurrence rate for unilateral hernia was also low. Therefore, the significantly higher risk for second repair in the unilateral group was probably mainly due to late occurrence of contralateral hernia rather than recurrence. In addition, children younger than 4 years were at a high risk of late occurrence of contralateral hernia after primary hernia repair [Table 2]. The calculated rates of late occurrence of contralateral hernia after primary unilateral hernia repair were 11.04%, 7.73%, and 3.28% for children aged 0–1, 1–4, and >4 years, respectively. In a related study, the rates of contralateral hernia among patients with primary unilateral hernia were 15%–29%, with 60% occurring within 2 years of the initial operation, and the remaining 40% occurring beyond 2 years of follow-up.[12] Tackett et al. reported an 8.8% overall incidence of late occurrence of contralateral hernia after primary hernia repair, including 12.4% among children <6 months of age and 10.6% among children <2 years of age.[13] In addition, Tsai et al. noted a 9.7% late occurrence rate of contralateral inguinal hernia after primary unilateral repair (mean, 4.9 years).[14] Lin et al. reported a 25% incidence of contralateral inguinal hernia after open primary repair (mean, 7.17 months)[15] and used mini-laparoscopy to examine the contralateral patent processus vaginalis in infants. Patent processus vaginalis on the contralateral side cannot be identified in primary unilateral hernia repair. In Lin et al.'s study, proactive closure of patent processus vaginalis reduced the late occurrence rate of contralateral hernia to 0. Efforts to prevent incidents that would necessitate second repair should be cautiously executed in this younger age group.

Steinau et al. collected 2754 pediatric cases and identified a higher recurrence rate among boys than girls. However, in our analysis of long-term follow-up data, we demonstrated that gender was not a risk factor for second hernia repair [Table 2]. Although Grosfeld et al.[8] and Steinau et al.[16] reported that recurrent hernia may be associated with prematurity, our study did not confirm prematurity as a risk factor for second repair [Table 2]. In addition, the literature suggests that other comorbid conditions may affect recurrence, including increased intra-abdominal pressure (ventriculoperitoneal shunts), growth failure, chronic pulmonary disease, bladder exstrophy, connective tissue disorders, cryptorchism, seizure disorder, and malnutrition.[8] In this study, cryptorchidism and congenital birth did not exhibit a significant influence on the incidence of second hernia repair. This disagreement may have been influenced by the fact that the NHIRD is a database and not a medical record; it may not have provided sufficiently detailed information on patient conditions and associated diseases due to coding errors. However, the referenced studies enrolled small numbers of patients and were mostly single-institution studies. Thus, their data may not exhibit sufficient power to prove correlations between the cited risk factors and incidence levels of second repair.

In the present study, specialty of surgeons was not a risk factor for hernia recurrence. Borenstein et al. collected 20,545 cases, among which pediatric surgeons performed 50.3% of procedures, with general surgeons performing 49.7%.[17] The recurrence rate was higher in the general surgeon group than in the pediatric surgeon group. However, in our findings, procedures performed by pediatric surgeons, general surgeons, and urologists corresponded with similar low rates of hernia recurrence [Table 2] and [Figure 3].

The present study exhibited strength based on the two main points. First, the NHIRD is a nationwide database and comprises a relatively large population. In theory, almost all inguinal hernia repairs performed in Taiwan can be identified in the NHIRD, even the surgeries were performed in different institutions. Second, this was a longitudinal cohort study; for the individuals in the study sample, all inguinal hernia repairs reported from birth to the end of life were considered. The observation period (11.4 ± 2.2 years) was long in comparison with those of related studies. Thus, our results regarding recurrence rate after pediatric inguinal hernia repair may be considered to be relatively reliable.

This study also had several limitations. Although we believe that our results are reliable because the NHI program covers more than 98% of the population in Taiwan, the actual recurrence rate is unknown. The second operations beyond the study period (1998–2012) of the dataset were not included in this study. The claim records of the NHIRD do not include detailed medical records; therefore, errors may have occurred in the present study's estimation of recurrent hernia after primary repair and contralateral occurrence based on the subsequent hernia repair. Furthermore, our recurrence rate was estimated based on the second repair rate, rather than the true recurrence rate of unilateral inguinal hernia repair. The study is lacking of second repair-associated complications. We did not analyze the impacts of surgical approach (open or laparoscopy) of the first repair on the recurrence. In addition, some individuals with recurrence may not have received operations or may have experienced recurrence after the endpoint time of data collection in this study.


  Conclusions Top


This nationwide longitudinal observation study indicated that the incidence of second repair after primary unilateral or bilateral inguinal hernia repair in children was 7.52%. The only risk factor predicting recurrence was age of <4 years at the time of initial operation; gender and prematurity were not identified as risk factors. The expected recurrence rate after any site of inguinal hernia repair in children was 0.69%.

Acknowledgment

This study was supported by the Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation (grant number: TCRD-TPE-103-RT-7).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

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    Tables

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