Management of inguinal hernia in premature infants: 10-year experience.

AIM: Debatable issues in the management of inguinal hernia in premature infants remain unresolved. This study reviews our experience in the management of inguinal hernia in premature infants.
MATERIALS AND METHODS: Retrospective chart review of premature infants with inguinal hernia from 1999 to 2009. Infants were grouped into 2: Group 1 had repair (HR) just before discharge from the neonatal intensive care unit (NICU) and Group 2 after discharge.
RESULTS: Eighty four premature infants were identified. None of 23 infants in Group 1 developed incarcerated hernia while waiting for repair. Of the 61 infants in Group 2, 47 (77%) underwent day surgery repair and 14 were admitted for repair. At repair mean postconceptional age (PCA) in Group1 was 39.5 ± 3.05 weeks. Mean PCA in Group 2 was 66.5 ± 42.73 weeks for day surgery infants and 47.03 ± 8.87 weeks for admitted infants. None of the 84 infants had an episode of postoperative apnea. Five (5.9%) infants presented subsequently with metachronous contralateral hernia and the same number of infants had hernia recurrence.
CONCLUSIONS: Delaying HR in premature infants until ready for discharge from the NICU allows for repair closer to term without increasing the risk of incarceration. Because of low occurrence of metachronous hernia contralateral inguinal exploration is not justified. Day surgery HR can be performed in former premature infant if PCA is >47 weeks without increasing postoperative complications.

INTRODUCTION

Inguinal hernia occurs more commonly in premature infants than in the general population with a reported incidence being up to 30%.[1] Controversial issues in the management of inguinal hernia in premature infants, include timing of repair, the need for contralateral inguinal exploration and the minimum postconceptional age (PCA) for day surgery repair. Optimal timing for inguinal hernia repair (HR) in a premature infant in the neonatal Intensive Care Unit (NICU) is still debated. Although some authors recommend early HR to prevent the risk of incarceration, others prefer delaying surgery until infants are ready to be discharged home.[2] Optimal timing must represent a balance of complications, including hernia incarceration against the risk of intraoperative and postoperative respiratory and surgical complications.[3] There is still no clear consensus as to routine contralateral inguinal exploration in the premature infant without clinical evidence of a hernia. Routine admission of former premature infants after general anesthesia for HR has been recommended because of postoperative respiratory complications, however, the minimum PCA for day surgery remains uncertain.

The aim of this study is to review our experience in the management of premature infants with inguinal hernia at King Abdulaziz Medical City-Riyadh (KAMC-R).

MATERIALS AND METHODS

After obtaining approval from the Scientific Research Committee at KAMC-R, a retrospective chart review was undertaken of premature infants (gestational age (GA) <37 weeks) diagnosed with inguinal hernia from January 1999 to December 2009. The practice at our institution is HR in premature infants just before discharge from NICU. The discharge criteria include:

Ability to feed orally and gaining weight,

Out of incubator and able to maintain vital parameters, including body temperature independently,

Weight >1750 g at discharge and

No apnea for 7 consecutive days while off theophylline and oxygen >72 h.

There were two groups of premature infants: Group 1 had HR in the NICU just before discharge, and Group 2 were former premature infants who had HR after discharge. The hospital practice is to admit a former premature infant whose PCA is <50 weeks for HR and 24 h apnea monitoring. Day surgery repair is for an infant whose PCA is >50 weeks. The data extracted from the charts included gender, GA, birth weight (BW), comorbidities, site(s) of inguinal hernia, age, and PCA at diagnosis of inguinal hernia. The age, PCA and body weight at HR, and postoperative complications were also obtained.

Hernia repair was performed by open method and under general and caudal anesthesia. The infants were reviewed in the pediatric surgery clinic 4–6 weeks after discharge.

Graph Pad QuickCalc Software was used for data analysis. Unpaired t-test and Fisher's exact χ2 analysis were performed and P < 0.05 was considered as significant.

RESULTS

A total of 84 premature infants’ charts were reviewed: 74 (88%) males and 10 females (male to female ratio, 7.4:1), 23 (Group 1) and 61 (Group 2) [Table 1]. Hernias were 33 (39%) right-sided, 26 (31%) left-sided, and 25 (30%) bilateral. Comorbidities were small for GA, bronchopulmonary dysplasia, necrotizing enterocolitis, intraventricular hemorrhage, and patent ductus arteriosus as shown in Tables 1 and 2. There was no report of testicular atrophy. Five (5.9%) infants presented with metachronous contralateral inguinal hernia within 10-1022 days (mean 266.6 days). Recurrent hernias were seen in 5 (5.9%) infants within a range of 47–715 days (mean 302 days). Two Infants had contralateral inguinal exploration for no visible hernia. Other procedures performed included circumcision (n = 35), orchiopexy (n = 1), and repair of esophageal atresia and tracheoesophageal fistula (n = 1). None of the 84 infants developed postoperative apnea.

Table 1

Demographic data and comorbidities of both groups

Table 2

Comparison of demographic data and comorbidities of premature infants operated after initial discharge

Group 1

Of 29 infants diagnosed with inguinal hernia in the NICU, 23 (79%) including one female had repair just before discharge. The hernia sites were nine right-sided, seven left-sided, and seven bilateral. None of the infants had an episode of incarceration before repair. Surgical complications included 3 (13%) infants with hernia recurrence and one with scrotal hematoma. Two infants were electively ventilated postoperatively for chronic lung disease. Metachronous contralateral inguinal hernia appeared in four infants.

Group 2

Sixty-one former premature infants included six infants with inguinal hernia diagnosed in the NICU; 47 (77%) had day surgery HR and 14 admitted for repair [Table 2]. Two male infants presented with incarcerated inguinal hernia and had repair after reduction. Metachronous contralateral inguinal hernia was found in one infant. Surgical complications included two infants with hernia recurrence, one infant with urinary bladder injury and another infant with surgical site infection. Comparing the body weight of former premature infants admitted for repair to day surgery infants showed statistical significance (P = 0.0039).

DISCUSSION

The risk for postoperative complications in premature infants undergoing HR is higher because of the technical difficulties from extreme friability of hernial sac and an increased frequency of concurrent medical problems.[14] Optimal timing for HR in premature infants must represent a balance of complications including hernia incarceration against the risk of intraoperative and postoperative respiratory and surgical complications.[3] Delaying HR until the infant is clinically stable for discharge allows for these medical conditions to be stabilized or resolved.[45] In this study, 79% of premature infants with inguinal hernia in the NICU had repair just before discharge. At repair, the mean PCA and mean body weight were 39.5 weeks and 2214 g, respectively. No infant had postoperative apneic episodes. Authors who recommend early HR are concerned about the risk of hernia incarceration before repair.[67] The incidence of incarcerated hernia in the premature infant waiting for HR is reported between 29.8% and 39%.[7] However, in this series no infant in the NICU had episodes of incarceration before HR, which supports the conclusions of a study by González Santacruz et al.[8] Therefore, delaying HR until discharge allows the premature infant to be operated on closer to term, which decreases the risk of postoperative apnea without increasing the risk of incarceration.

Postoperative apnea in premature infants is inversely related to GA and PCA and the incidence is less than 5% when the PCA is >60 weeks.[9] If there is no history of apnea or chronic lung disease, Lee et al.,[10] propose that former premature infants with PCA between 41 and 46 weeks can safely undergo outpatient herniorrhaphy. Our hospital policy requires all former premature infants with PCA <50 weeks to be admitted for HR and 24-h postoperative apnea monitoring. A recent meta-analysis recommended that former premature infants undergoing general anesthesia with PCA <46 weeks should be observed for at least 12 h postoperatively, but individualized patient care should be based on associated comorbidities for those between 46 and 60 weeks PCA.[11] Laituri et al.,[12] had reported overnight observation after HR for premature infants <50 weeks PCA. A high percentage of these premature infants had a postoperative event related to apnea in the recovery room, but not overnight. Due to the evolution of anesthetic practice, and the use of newer less soluble volatile anesthetic agents, infants have faster awakening in the recovery room.[12] Therefore, the incidence of apnea may have changed over the past decade as new agents are being used for general anesthesia. Murphy et al.,[13] believe that the risk of apnea is much lower in the current anesthetic practice. Lee et al.,[10] have questioned routine hospital admission because of the minimal risk of postoperative apnea in former premature infants undergoing elective HR. In this study, the mean PCA for former premature infants admitted for HR and day surgery infants is 47 weeks and 66.5 weeks respectively; and no infant had a postoperative apneic episode. A study by Ozdemir and Arikan showed the rate of postoperative apnea in a former premature infant older than 45 weeks as 0.8%.[14] They concluded that infants with PCA >45 weeks and without comorbidities may undergo day surgery HR. Despite the flaws in retrospective studies and a small number of patients in this study, with the current general anesthetic agents, former premature infants with PCA >47 weeks may undergo day surgery HR without increasing the risk of postoperative apnea.

In our study, metachronous contralateral inguinal hernia was found in 5.9% of premature infants. The incidence of metachronous inguinal hernia in premature infants has been reported between 7% and 14.8%.[1516] Exploration of an asymptomatic inguinal side is to detect a patent processus vaginalis or a hernia, so as to avoid the chance of a contralateral inguinal hernia incarceration and second anesthesia. However, the presence of patent processus vaginalis does not mean that the infant will develop an inguinal hernia.[1] In a prospective study of 264 premature and term infants who developed metachronous inguinal hernias, Marulaiah et al.,[15] concluded that routine contralateral exploration is not indicated because of the risk of spermatic cord injury and low occurrence.

The hernia recurrence rate of 5.9% in our series is within the reported range of 2.6-8.6%.[17] Vaos et al.,[7] had reported a hernia recurrence rate of 12.1% and 14.1% if HR is early or delayed, respectively. They suggested that repair of incarcerated inguinal hernia is associated with a high likelihood of recurrence because of technical difficulties from edematous and friable sac. Vogels et al.,[17] found a recurrence of 62.5% in premature boys who underwent HR and concluded that large hernial sacs, inadvertent opening of sacs, low gestation, and specific comorbidities such as the presence of ventriculoperitoneal shunt or connective tissue disease are associated with a higher likelihood of recurrence.

Laparoscopic HR in premature infants has been reported recently with postoperative complications similar to those reported by open technique.[181920] In a retrospective analysis of 67 infants weighing 3 kg or less (64 premature), who underwent laparoscopic HR, hernia recurrence was 4.4%.[19] One disadvantage of laparoscopy in the premature is the need for endotracheal intubation and assisted respiratory ventilation. However, in laparoscopic repair there is no difference in the access for either unilateral or bilateral hernia. Although laparoscopic HR is considered as a safe, procedure a structured training program is required for trainees to ensure satisfactory outcome.[21]

The limitations with this retrospective study include inadequate data collection from medical charts because of poor documentation, undetected or unreported episodes of apnea, and small number of infants.

CONCLUSION

Delaying HR in a premature infant in the NICU to just before discharge allows for repair closer to term without increasing the risk of incarceration. Because of low occurrence of metachronous inguinal hernia contralateral inguinal exploration is not justified. A former premature infant may undergo day surgery HR as day surgery if the PCA is > 47 weeks without increased risk of postoperative apnea. However, a multicentered prospective study is required to establish the minimum PCA for former premature infants to undergo day surgery HR.