Abstract
Purpose:
Inguinal hernias are common in premature infants, but there is substantial variation with regards to timing of repair. We sought to quantify and explain this variation.
Methods:
Cohort study of infants <34 weeks gestation diagnosed with an inguinal hernia and discharged from one of 329 neonatal intensive units between 1998 and 2012. Multivariable logistic regression clustered by site was used to evaluate demographic, clinical, maternal, and socioeconomic variables associated with pre-discharge repair.
Results:
A total of 8037 infants met study criteria, and 3230 (40%) received a pre-discharge repair. The frequency of pre-discharge repair varied by site from 9% to 84%, and increased over the study period from 20% in 1998 to 45% in 2012. Concurrent gastrostomy or fundoplication and lower socioeconomic status were associated with an increased odds of receiving a pre-discharge repair.
Conclusion:
There is substantial variation with regards to the timing of repair of inguinal hernias in premature infants, with an increasing number of infants receiving repair prior to hospital discharge over time. Concurrent gastrostomy or fundoplication and socioeconomic status are associated with timing of repair.
Keywords: Inguinal Hernia Repair, Premature Infant
1.0. Introduction
Inguinal hernias are common in children, affecting roughly 1–4% of infants born at term, and 30% of infants born prematurely. [1, 2] Due to the risk of incarceration and strangulation, infants hospitalized in the neonatal intensive care unit (NICU) with inguinal hernias often undergo repair prior to discharge. Proponents of pre-discharge repair cite a risk of hernia incarceration among infants as high as 35%, often within the first week of diagnosis and before an elective hernia repair can be performed. [3, 4] One study found that a delay of only 14 days between diagnosis and operative repair results in an almost two-fold increased risk of incarceration. [5]
Alternatively, some surgeons opt to discharge the infant with a plan for elective repair at a later date. This allows time for the infant to grow, possibly leading to a technically easier repair, which may reduce intraoperative complications including inadvertent entering of the hernia sac, increasing the risk of recurrence. [6, 7] Furthermore, a longer waiting period may reduce the risk of post-operative apnea and other anesthetic complications among premature infants, and at least one study has demonstrated that delayed repair may lead to reduced rates of recurrence. [8–10] Despite these benefits, proponents of delayed repair often require that the infant be discharged to caregivers likely to return for emergent assistance should the hernia become incarcerated. It is unclear, however, what the general practice is on a national level or what factors influence the decision to perform an early vs delayed hernia repair. Recent surveys have demonstrated that there is still substantial practice variability regarding this matter. [11, 12] This study was performed to evaluate the current national trends regarding timing of inguinal hernia repair in premature infants, as well as to determine factors associated with the decision to perform early vs late repair.
2.0. Materials and Methods
2.1. Data Source
We used an electronic medical record database that prospectively captures information generated by clinicians on all infants cared for by the Pediatrix Medical Group in one of 348 neonatal intensive care units (NICUs) in North America. This information includes data on multiple aspects of care garnered from admission notes, daily progress notes, and discharge summaries and includes maternal history, demographics, medications, laboratory results, diagnoses, and procedures. These data are then transferred to the Pediatrix Clinical Data Warehouse for quality improvement and research purposes. [13]
2.2. Patient Population
Institutional review board approval was obtained prior to data analysis. Infants were included if they were born at <34 weeks gestation, diagnosed with an inguinal hernia, and discharged from a Pediatrix Medical Group NICU between 1998 and 2012. Infants transferred to another hospital or who died during their hospitalization were excluded. Infants were grouped based on whether they received a pre-discharge inguinal hernia repair or were discharged without repair.
2.3. Statistical Analysis
We calculated the proportion of infants who received an inguinal hernia repair prior to discharge by center for centers that reported five or more inguinal hernia repairs during the study period. In order to determine trends in the pre-discharge repair of inguinal hernias over the study period, we calculated a chi-square statistic for the regression of the proportion of infants who received pre-discharge repair by discharge year.
Using all infants included in the study population, infants were grouped depending on whether they received a pre-discharge inguinal hernia repair or were discharged without repair. Groups were then compared on baseline characteristics including gestational age, sex, race/ethnicity, birth weight, small for gestational age status, concurrent umbilical hernia repair, concurrent gastrostomy or fundoplication during initial hospitalization, bronchopulmonary dysplasia (defined as continuous oxygen or any respiratory support requirement between postmenstrual age 36 0/7 weeks and 36 6/7 weeks), and the presence of a major congenital anomaly.[14] Since 2010, the dataset has also included maternal home address This allowed us to link home address to census variables at the block group level via shared geography and to calculate distance from the home address to the reference institution. Thus for infants discharged from 2010–2012, we also included U.S. census block group poverty level and educational attainment data, as well as distance from the primary treatment center. We therefore then identified only infants discharged from 2010–2012, repeated the above comparisons, and compared the groups according to specific socioeconomic variables. All comparisons were performed using Fisher’s exact test. Some continuous variables were separated into groups in order to ease interpretation of the results. The cut-offs for this selection were determined a priori based on clinical significance.
In order to determine the adjusted association of infant-related factors and the odds of receiving a pre-discharge inguinal hernia repair, a mixed effects logistic regression was performed among the cohort of infants hospitalized between 2010 and 2012. Variables included as fixed effects in this model were determined a priori and included gestational age, sex, race, small for gestational age status, concurrent umbilical hernia diagnosis, creation of a gastrostomy or fundoplication during the index hospitalization, bronchopulmonary dysplasia, percentage of households in infant’s U.S. census block group below the poverty level, percentage of infant’s U.S. census block group with high school diploma or GED equivalent, and distance from hospital (in miles). Hospital site was also included in the model as a random effect.
Two-tailed p-values of <0.05 were considered statistically significant. All statistical analyses were performed using Stata14.1 (College Station, TX).
3.0. Results
A total of 8037 infants were diagnosed with an inguinal hernia during the study period and 3230 (40%) received an inguinal hernia repair prior to discharge. There was substantial variation by center regarding the performance of a pre-discharge repair (Figure 1). Over the study period, the proportion of infants who received a pre-discharge repair increased from 20% in 1998 to 45% in 2012 (Figure 2, p<0.01).
Figure 1:
Variation in the performance of an inguinal hernia repair prior to discharge among infants diagnosed with an inguinal hernia at centers reporting at least five hernias over the study period (Median: 52%, Interquartile Range: 35%, 64%).
Figure 2:
Incidence of inguinal hernia repair prior to discharge over time among infants diagnosed with an inguinal hernia.
In unadjusted analysis of the overall cohort, infants who received an in-hospital inguinal hernia repair were more likely to be white (53% vs 50%) and were more likely to be <1000 g at birth (68% vs 63%, Table 1). Within the 2010–2012 cohort, race, birth weight, small for gestational age status, presence of bronchopulmonary dysplasia, and the presence of a concurrent umbilical hernia were all found to be significantly associated with pre-discharge inguinal hernia repair in unadjusted analysis. Although not statistically significant, there was also an association between the percentage of families living below the poverty level among the infant’s U.S. census block group and undergoing a pre-discharge inguinal hernia repair. The same was true for the percentage of individuals with a high school diploma or GED equivalent in the infant’s U.S. census block group. There was no significant association between the distance the family lived from the hospital and the timing of repair.
Table 1:
Baseline characteristics by group both among the entire cohort (1998–2012) and among the cohort with socioeconomic data available (2010–2012).
| Entire Cohort (1998–2012) | Select Cohort (2010–2012) | |||||
|---|---|---|---|---|---|---|
| In-Hospital Inguinal Hernia Repair | No In-Hospital Inguinal Hernia Repair | p | In-Hospital Inguinal Hernia Repair | No In-Hospital Inguinal Hernia Repair | p | |
| N | 3230 | 4807 | 1090 | 1362 | ||
| Gestational age, weeks | <0.01 | 0.09 | ||||
| <27 | 1462 (45%) | 1954 (41%) | 487 (45%) | 551 (41%) | ||
| 27–30 | 1400 (43%) | 2143 (45%) | 459 (42%) | 605 (44%) | ||
| >30 | 368 (11%) | 710 (15%) | 144 (13%) | 206 (15%) | ||
| Female | 577 (18%) | 873 (18%) | 0.75 | 220 (20%) | 265 (20%) | 0.68 |
| Race/Ethnicity | <0.01 | <0.01 | ||||
| White | 1662 (53%) | 2331 (50%) | 519 (50%) | 640 (49%) | ||
| Black | 703 (23%) | 1236 (27%) | 270 (26%) | 394 (30%) | ||
| Hispanic | 583 (19%) | 811 (17%) | 194 (19%) | 188 (14%) | ||
| Other | 165 (5%) | 282 (6%) | 58 (6%) | 91 (7%) | ||
| Birth weight, g | <0.01 | 0.01 | ||||
| <1000 | 2202 (68%) | 3046 (63%) | 719 (66%) | 826 (61%) | ||
| 1000–1499 | 816 (25%) | 1399 (29%) | 293 (27%) | 425 (31%) | ||
| 1500–1999 | 166 (5%) | 302 (6%) | 63 (5.8%) | 100 (7%) | ||
| ≥2000 | 43 (1%) | 55 (1%) | 15 (1%) | 11 (1%) | ||
| Small for gestational age | 962 (30%) | 1349 (28%) | 0.10 | 326 (30%) | 352 (26%) | 0.03 |
| Concurrent umbilical hernia | 188 (6%) | 278 (6%) | 0.96 | 86 (8%) | 141 (10%) | 0.04 |
| Gastrostomy or fundoplication | 342 (11%) | 154 (3%) | <0.01 | 151 (14%) | 55 (4.0%) | <0.01 |
| Bronchopulmonary dysplasia | 1690 (55%) | 2056 (45%) | <0.01 | 550 (53%) | 575 (44%) | <0.01 |
| Major congenital anomaly | 310 (10%) | 401 (8%) | 0.05 | 98 (9%) | 104 (8%) | 0.23 |
| Percentage Below Poverty Level* | 0.06 | |||||
| <5% | 166 (22%) | 250 (27%) | ||||
| 5–20% | 356 (47%) | 407 (44%) | ||||
| >20% | 240 (32%) | 275 (30%) | ||||
| Percentage with High School or GED Equivalent* | 0.07 | |||||
| <75% | 206 (27%) | 210 (23%) | ||||
| 75–90% | 295 (39%) | 364 (39%) | ||||
| ≥90% | 261 (34%) | 358 (38%) | ||||
| Distance from Hospital (miles)* | 0.81 | |||||
| <10% | 282 (37%) | 340 (36%) | ||||
| 10–20% | 192 (25%) | 227 (24%) | ||||
| ≥20% | 287 (38%) | 366 (39%) | ||||
Socioeconomic data is only available for patients discharged from 2010 to 2012.
On multivariable analysis, creation of a gastrostomy or fundoplication (adjusted odds ratio, AOR [95% confidence interval, CI]: 3.07 [1.87, 5.05]), living in a U.S. census block group with 5–20% of households living below the poverty level (1.62 [1.13, 2.34]), and living in a U.S. census block group with >20% of households living below the poverty level (1.62 [1.03, 2.56]), were found to be associated with a significantly increased odds of receiving an inguinal hernia repair prior to discharge (Figure 3).
Figure 3:
Variables associated with receiving a pre-discharge inguinal hernia repair.
4.0. Discussion
Inguinal hernia repair is one of the most common surgical procedures performed in children. [15] Nonetheless, there is substantial debate regarding the optimal timing of repair for premature infants with inguinal hernias diagnosed in the NICU. In this study, we demonstrated that there is considerable center variation with regards to performing inguinal hernia repairs prior to discharge from the NICU. We also found that the percentage of pre-discharge repairs actually increased over the study period. Lastly we found that specific factors, such as undergoing a gastrostomy or fundoplication and lower socioeconomic status, were also significantly associated with increased odds of receiving a pre-discharge inguinal hernia repair.
The variability in pre-discharge repair is likely secondary to the substantial variation in surgeon and center opinion with regards to this issue. Some studies have suggested benefit for earlier repair due to a relatively high incidence of incarceration among infants waiting for a repair. [5, 8] Conversely, other studies have not demonstrated a high incidence of incarceration among infants discharged from the hospital with planned elective repair, and furthermore, delayed repair may reduce the risk of apnea associated with surgical procedures in preterm infants. [16–18] In a study of 2030 infants with an inguinal hernia, Sulkowski and colleagues also found substantial variation by institution in the percentage hernia repairs being performed prior to discharge, from 26% to 97%. [9] Contrary to our study, they found no significant change in the rate of pre-discharge repair between 1999 and 2012. In our study, we found a significant increase in the rate of pre-discharge repair over the study period. It is unclear why exactly this occurred; however, as there were no major changes in national guidelines at this time it is likely that there were changes in overall surgeon opinion favoring pre-discharge repair during the late 1990s.
The association of socioeconomic status and odds of receiving a pre-discharge repair is a novel finding. We found that infants who lived in U.S. census block groups in which >5% of the population lived below the poverty level were significantly more likely to undergo a pre-discharge hernia repair than infants from U.S. census block groups with <5% of the population living under the poverty level. It is hypothesized that this may be due to physician concerns that families from lower socioeconomic backgrounds may be less likely to follow-up for elective hernia repair following discharge. It is unclear, however, if there is any evidence to support this notion. Wang and colleagues found that socioeconomic disparities are associated with reduced compliance after ED visits among children. [19] However, other studies have found that socioeconomic factors are not necessarily associated with disparities in medical follow-up. [20] Further investigation is needed to explore what impact socioeconomic factors may have on clinical decision-making.
Research, especially in animal studies, have indicated that early exposure to anesthetic drugs among infants can have long-term neurobehavioral consequences, although this association was not supported in two recently published large randomized trials. [21–24] Despite this debate, this concern may also lead to the association between pre-discharge hernia repair and concurrent surgical procedures we found in this study. In order to reduce the need for a second anesthetic exposure later in life, surgeons were more likely to repair an infant’s hernia at the time of the gastrostomy or fundoplication, instead of delaying until after discharge.
This study includes patients from across the United States leading to the inclusion of a diverse group of centers, thus improving the generalizability of our findings over smaller studies. By linking the maternal home address to census variables at the block group level, we were able to investigate the association of important socioeconomic variables with the timing of inguinal hernia repair. The integration of this data with the Pediatrix Clinical Data Warehouse has the potential for many other important studies which can incorporate important socioeconomic surrogates in the statistical modeling.
Our study has several limitations. First, due to the retrospective nature of this study and the use of a large multi-center database, there are unmeasured confounders which may have had an impact on the decision to perform a pre vs post-discharge inguinal hernia repair that we could not account for in our model. For example, we were unable to identify certain specific signs and symptoms such as incarceration which may have impacted the timing of repair. Second, we do not have the ability to determine how many infants discharged without repair later received a repair. Lastly, due to the fact that socioeconomic data only became available in 2010, and the importance of keeping these variables in the model, we were only able to build our full model on a limited number of infants, thus reducing the power to detect significant associations.
5.0. Conclusions
In this study, we have demonstrated that there is not only substantial variation by center with regards to the timing of repair of inguinal hernias among premature infants, but also that there has been a slow trend towards increasing repair prior to initial hospital discharge. Furthermore, we have demonstrated that socioeconomic status is significantly associated with the timing of hernia repair. Based on the high level of variability in the timing of inguinal hernia repair among infants, as well as the scarcity of evidence supporting either method, further prospective randomized trials are necessary in order to better understand the impact of early vs delayed inguinal hernia repair in this population. A prospective multi-center study which is currently enrolling patients is likely to contribute important evidence to this topic (ClinicalTrials.gov Identifier: NCT01678638). [25]
Acknowledgments
Source of Funding: Dr. Smith receives salary support for research from the NIH and the National Center for Advancing Translational Sciences of the NIH (HHSN267200700051C, HHSN275201000003I, and UL1TR001117); he also receives research support from industry for neonatal and pediatric drug development (www.dcri.duke.edu/research/coi.jsp). Dr. Blakely receives support from the NIH (U01HD076733 and R01HD086792). Dr. Greenberg receives support from the NIH (5T32HD043029–1, HHSN 275201000003I, and HHSN272201300017I).
The funding bodies played no role in the study design; collection, analysis, and interpretation of data; the writing of the manuscript; or the decision to submit the manuscript for publication. Dr. Gulack wrote the first draft of the manuscript and received no honorarium for his effort.
6.0 References:
- 1.Harper RG, Garcia A, Sia C. Inguinal hernia: a common problem of premature infants weighing 1,000 grams or less at birth. Pediatrics 1975;56: 112–115. [PubMed] [Google Scholar]
- 2.Inguinal hernias and hydroceles in infancy and childhood: A consensus statement of the Canadian Association of Paediatric Surgeons. Paediatrics & Child Health 2000;5: 461–462. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Stylianos S, Jacir NN, Harris BH. Incarceration of inguinal hernia in infants prior to elective repair. J Pediatr Surg 1993;28: 582–583. [DOI] [PubMed] [Google Scholar]
- 4.Lautz TB, Raval MV, Reynolds M. Does timing matter? A national perspective on the risk of incarceration in premature neonates with inguinal hernia. The Journal of pediatrics 2011;158: 573–577. [DOI] [PubMed] [Google Scholar]
- 5.Zamakhshary M, To T, Guan J, Langer JC. Risk of incarceration of inguinal hernia among infants and young children awaiting elective surgery. Cmaj 2008;179: 1001–1005. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Vogels HD, Bruijnen CJ, Beasley SW. Predictors of recurrence after inguinal herniotomy in boys. Pediatr Surg Int 2009;25: 235–238. [DOI] [PubMed] [Google Scholar]
- 7.Lau ST, Lee YH, Caty MG. Current management of hernias and hydroceles. Semin Pediatr Surg 2007;16: 50–57. [DOI] [PubMed] [Google Scholar]
- 8.Vaos G, Gardikis S, Kambouri K, Sigalas I, Kourakis G, Petoussis G. Optimal timing for repair of an inguinal hernia in premature infants. Pediatr Surg Int 2010;26: 379–385. [DOI] [PubMed] [Google Scholar]
- 9.Sulkowski JP, Cooper JN, Duggan EM, Balci O, Anandalwar SP, Blakely ML, Heiss K, Rangel S, Minneci PC, Deans KJ. Does timing of neonatal inguinal hernia repair affect outcomes? J Pediatr Surg 2015;50: 171–176. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Duggan EM, Patel VP, Blakely ML. Inguinal hernia repair in premature infants: more questions than answers. Arch Dis Child Fetal Neonatal Ed 2015;100: F286–288. [DOI] [PubMed] [Google Scholar]
- 11.Wiener ES, Touloukian RJ, Rodgers BM, Grosfeld JL, Smith EI, Ziegler MM, Coran AG. Hernia survey of the Section on Surgery of the American Academy of Pediatrics. J Pediatr Surg 1996;31: 1166–1169. [DOI] [PubMed] [Google Scholar]
- 12.Antonoff MB, Kreykes NS, Saltzman DA, Acton RD. American Academy of Pediatrics Section on Surgery hernia survey revisited. J Pediatr Surg 2005;40: 1009–1014. [DOI] [PubMed] [Google Scholar]
- 13.Spitzer AR, Ellsbury DL, Handler D, Clark RH. The Pediatrix BabySteps Data Warehouse and the Pediatrix QualitySteps improvement project system--tools for “meaningful use” in continuous quality improvement. Clin Perinatol 2010;37: 49–70. [DOI] [PubMed] [Google Scholar]
- 14.Olsen IE, Groveman SA, Lawson ML, Clark RH, Zemel BS. New intrauterine growth curves based on United States data. Pediatrics 2010;125: e214–224. [DOI] [PubMed] [Google Scholar]
- 15.Sømme S, Bronsert M, Morrato E, Ziegler M. Frequency and variety of inpatient pediatric surgical procedures in the United States. Pediatrics 2013;132: e1466–e1472. [DOI] [PubMed] [Google Scholar]
- 16.Lee SL, Gleason JM, Sydorak RM. A critical review of premature infants with inguinal hernias: optimal timing of repair, incarceration risk, and postoperative apnea. J Pediatr Surg 2011;46: 217–220. [DOI] [PubMed] [Google Scholar]
- 17.Cote CJ, Zaslavsky A, Downes JJ, Kurth CD, Welborn LG, Warner LO, Malviya SV. Postoperative apnea in former preterm infants after inguinal herniorrhaphy. A combined analysis. Anesthesiology 1995;82: 809–822. [DOI] [PubMed] [Google Scholar]
- 18.Gholoum S, Baird R, Laberge J-M, Puligandla PS. Incarceration rates in pediatric inguinal hernia: do not trust the coding. Journal of pediatric surgery 2010;45: 1007–1011. [DOI] [PubMed] [Google Scholar]
- 19.Wang NE, Gisondi MA, Golzari M, van der Vlugt TM, Tuuli M. Socioeconomic disparities are negatively associated with pediatric emergency department aftercare compliance. Acad Emerg Med 2003;10: 1278–1284. [DOI] [PubMed] [Google Scholar]
- 20.McPherson ML, Lairson DR, Smith EO, Brody BA, Jefferson LS. Noncompliance with medical follow-up after pediatric intensive care. Pediatrics 2002;109: e94. [DOI] [PubMed] [Google Scholar]
- 21.Sun L Early childhood general anaesthesia exposure and neurocognitive development. British journal of anaesthesia 2010;105: i61–i68. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Flick RP, Katusic SK, Colligan RC, Wilder RT, Voigt RG, Olson MD, Sprung J, Weaver AL, Schroeder DR, Warner DO. Cognitive and behavioral outcomes after early exposure to anesthesia and surgery. Pediatrics 2011;128: e1053–1061. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Davidson AJ, Disma N, De Graaff JC, Withington DE, Dorris L, Bell G, Stargatt R, Bellinger DC, Schuster T, Arnup SJ. Neurodevelopmental outcome at 2 years of age after general anaesthesia and awake-regional anaesthesia in infancy (GAS): an international multicentre, randomised controlled trial. The Lancet 2016;387: 239–250. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.Sun LS, Li G, Miller TL, Salorio C, Byrne MW, Bellinger DC, Ing C, Park R, Radcliffe J, Hays SR, DiMaggio CJ, Cooper TJ, Rauh V, Maxwell LG, Youn A, McGowan FX. Association Between a Single General Anesthesia Exposure Before Age 36 Months and Neurocognitive Outcomes in Later Childhood. Jama 2016;315: 2312–2320. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.NCT01678638: Timing of Inguinal Hernia Repair in Premature Infants. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT01678638?term=NCT01678638&rank=1 [accessed 05.12.16].