15 - Risk Factors Associated with Inguinal Hernia Diagnosis in Infants Admitted to the NICU

Poster Number: 15
Publication Number: 15.337

Dale R. Gerstmann, Timpanogos Regional Hospital, Orem, UT, United States; Stephen W. Bickler MD, University of California San Diego, San Diego, CA, United States; Reese H. Clark, MEDNAX, Myrtle Beach, SC, United States

Background: Inguinal hernia (IH) in the neonate is a consequence of developmentally weak inguinal structures for which sufficient intra-abdominal pressure is present to push viscera into the process vaginalis. IH occurs in up to 13% of preterm infants < 33wks EGA and in 3-5% of term infants. Repair of IH is the most common surgical procedure performed in infancy. 45% of NICU infants with IH undergo surgical repair before hospital discharge. 56% of these will be surgical emergencies with a subsequent complication rate of 27% and a recurrence rate of 14%. Identifying NICU infants at the highest risk for IH can aid in providing proactive care.

Objective: To characterize IH risk in infants admitted for NICU care.

Design/Methods: This study is a retrospective review of de-identified patient data from 351 NICUs, comprising 1.4 million records in the Pediatrix Clinical Data Warehouse covering infants who survived for at least 7d and were discharged from NICU care between 1/1/1997 and 12/31/2018. Multivariate analysis of 10 common demographic factors was performed to identify those most associated with IH. These were compared to the base IH frequency and then used to directly calculate observed to expected (O/E) case ratios for the diagnosis of IH with neonatal abdominal conditions [gastroschisis, omphalocele, congenital diaphragmatic hernia (CDH), necrotizing enterocolitis (NEC)], and for a subset of 103 sites each having at least 5000 patients in the dataset.

Results: The base frequency of IH diagnosis in the dataset was 149 per 10,000 patients (1.49%). The demographic factors most associated with a NICU diagnosis of IH were EGA at birth (23-42 wk), gender (M, F), birth size (SGA, AGA, LGA), and race/ethnicity (Asian, Black, Hispanic, White, Other) p < 0.0001 each. The frequency of IH for each factor compared to base frequency is shown in Fig 1. Frequency ratios were elevated for infants with low EGA, male gender, SGA size, and black race, but decreased for EGA >32wks, female gender, LGA size, and Hispanic ethnicity. O/E ratios (Fig 2) were significantly elevated for diagnoses of gastroschisis (2.38), omphalocele (6.12), CHD (6.59), and for suspected and non-surgical NEC (1.40 and 1.26, respectively). The O/E site subset analysis (see Fig 3) indicated a 7.42 fold range in IH risk (0.33 to 2.45).Conclusion(s): Demographic factors are highly associated with IH risk in NICU infants, as well as neonatal abdominal conditions commonly associated with increased intra-abdominal pressure. Very high site variation suggests local care processes also influence IH risk and may thus be amenable to process improvement efforts.
Fig 1 - Demographic FactorsInguinal hernia (IH) frequency as a ratio to base frequency (1.49%) for the four most significant demographic factors.
FIg 3 - Site Variation in IH RiskInguinal hernia (IH) Risk as Observed/Expected (O/E) ratio for 103 Pediatrix NICUs with 5000 or more patients in the dataset, ordered from lowest IH risk to highest IH risk. There is a 7.42 fold difference in risk between the sites with the lowest and highest IH O/E ratio.