RESEARCH ARTICLE

Pyloric Stenosis: National Trends in the IncidenceRate and Resource Use in the United States From2012 to 2016Keyur Donda, MBBS,a Barbara Asare-Afriyie, MB ChB,b Marian Ayensu, MB ChB,c Mayank Sharma, MBBS,d Jason K. Amponsah, MB ChB,c Parth Bhatt, MD, MPH,e

Matilda Adobea Hesse, MB ChB,f Fredrick Dapaah-Siakwan, MDg

A B S T R A C T OBJECTIVES: Infantile hypertrophic pyloric stenosis (IHPS) is the most common reason forabdominal surgery in infants; however, national-level data on incidence rate and resource use arelacking. We aimed to examine the national trends in hospitalizations for IHPS and resource use inits management in the United States from 2012 to 2016.

METHODS: We performed a retrospective serial cross-sectional study using data from the NationalInpatient Sample, the largest health care database in the United States. We included infantsaged #1 year assigned an International Classification of Diseases, Ninth Revision, or InternationalClassification of Diseases, 10th Revision, code for IHPS who underwent pyloromyotomy orpyloroplasty. We examined the temporal trends in the incidence rate (cases per 1000 live births)according to sex, insurance status, geographic region, and race. We examined resource use usinglength of stay (LOS) and hospital costs. Linear regression was used for trend analysis.

RESULTS: Between 2012 and 2016, there were 32 450 cases of IHPS and 20 808 149 live births(incidence rate of 1.56 per 1000). Characteristics of the study population were 82.7% male, 53%white, and 63.3% on Medicaid, and a majority were born in large (64%), urban teaching hospitals(90%). The incidence of IHPS varied with race, sex, socioeconomic status, and geographic region.In multivariable regression analysis, the incidence rate of IHPS decreased from 1.76 to 1.57 per1000 (adjusted odds ratio 0.93; 95% confidence interval 0.92–0.93). The median cost of care was$6078.30, whereas the median LOS was 2 days, and these remained stable during the period.

CONCLUSIONS: The incidence rate of IHPS decreased significantly between 2012 and 2016,whereas LOS and hospital costs remained stable. The reasons for the decline in the IHPS incidencerate may be multifactorial.

aDivision of Neonatology,Department of Pediatrics,

University of SouthFlorida, Tampa, Florida;bSchool of Public Healthand Tropical Medicine,Tulane University, New

Orleans, Louisiana;cDepartment of Medicine,The Trust Hospital, Accra,

Ghana; dBatchelorChildren’s Research

Institute, Miller School ofMedicine, University ofMiami, Miami, Florida;

eDepartment ofPediatrics, Health

Sciences Center, TexasTech University, Amarillo,Texas; fKorle-Bu TeachingHospital, Accra, Ghana;

and gDepartmentof Pediatrics, School ofMedicine, University of

Connecticut, Farmington,Connecticut

www.hospitalpediatrics.orgDOI:https://doi.org/10.1542/hpeds.2019-0112Copyright © 2019 by the American Academy of Pediatrics

Address correspondence to Fredrick Dapaah-Siakwan, MD, Valley Children’s Healthcare, 9300 Valley Children’s Place, SE 20, Madera, CA93636. E-mail: fdapaahsiakwan@valleychildrens.com

HOSPITAL PEDIATRICS (ISSN Numbers: Print, 2154-1663; Online, 2154-1671).

FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.

FUNDING: No external funding.

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

COMPANION PAPER: A companion to this article can be found online at www.pediatrics.org/cgi/doi/10.1542/peds.2019-0254.

Drs Donda and Dapaah-Siakwan conceptualized and designed the study, drafted the initial manuscript, designed the data collectioninstruments, coordinated the supervised data collection, and critically reviewed the manuscript; Drs Bhatt and Asare-Afriyieconceptualized and designed the study and drafted the initial manuscript; Drs Ayensu, Sharma, Amponsah, and Hesse carried out theinitial analyses and reviewed and revised the manuscript; and all authors approved the final manuscript as submitted.

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Infantile hypertrophic pyloric stenosis(IHPS) is the most common reasonfor abdominal surgery in the first6 months of life.1,2 Most infants withIHPS present with signs and symptomswithin the first 2 to 12 weeks of life.The exact etiology of IHPS is unknown,but environmental factors such asmaternal smoking and alcohol useduring pregnancy, exposure of infantsto macrolides, prematurity, bottle-feeding,and genetic factors have been implicatedin the occurrence of the condition.3,4 Theincidence rate varies over time andgeographic region. In the United States,the rate varies from 1.33 to 3 per1000 live births depending on the statewhere the study was conducted and thetype of data used.5–10 The nationwideincidence rate of IHPS in the United Statesis unknown. Recent studies fromother countries have revealed that theincidence rate of IHPS is declining11–13 orincreasing.14,15 Authors of a few studiesconducted in the United States haveexamined the trends in the incidencerate of IHPS. Most of them werecompleted before 2003 in specificgeographic regions in the UnitedStates.6,7,16–18 One recent study in whichauthors used data from a birth defectsurveillance registry from 11 states inthe United States revealed a downwardtrend in the incidence rate of IHPS from2007 to 2010 despite an overall stable trendbetween 1999 and 2010.8 Authors fromanother study examined data from theUS Military Health System and found nosignificant change in the incidence rate ofIHPS between 2001 and 2012.9 Althoughthese studies provide useful information onthe incidence rate of IHPS, they are limitedto a few states, are not nationallyrepresentative, and thus may lack externalvalidity. Furthermore, national-levelestimates of resource use (length of stay[LOS] and hospital cost) in the managementof IHPS are lacking. In the current study, wesought to determine the temporal trends inthe incidence rate of IHPS hospitalizationsand the associated resource use in itsmanagement from 2012 through 2016 usingdata from the National Inpatient Sample(NIS).

METHODSStudy Design and Data Source

We performed a retrospective serial cross-sectional analysis of data from the NIS from2012 through 2016. The raw data wereobtained from the Agency for HealthcareResearch and Quality (https://www.hcup-us.ahrq.gov). The NIS, a part of theHealthcare Cost and Utilization Project(HCUP), sponsored by the Agency forHealthcare Research and Quality,19 is thelargest publicly available all-payer inpatienthealth care database in the United States.The NIS represents a random 20% stratifiedsample of all discharges in the UnitedStates. The sampling frame included44 states from 2012 through 2014, 46 statesin 2015, and 47 states, including the Districtof Columbia, in 2016. Supplemental Fig 3reveals the HCUP partner states in each ofthe census regions as of 2014. Unweighted,the 20% stratified sample contains 7 millionhospital stays each year. When weighted, theNIS estimates .35 million hospitalizationsnationally each year. This sampling framerepresents.97% of the US population. Eachindividual hospitalization in this database isdeidentified and maintained as a uniqueentry with 1 primary discharge diagnosis,,30 secondary diagnoses along, and,15 procedure codes during thathospitalization. Researchers and policymakers use the NIS to make nationalestimates of health care use, access,charges, quality, and outcomes. The NIS wasredesigned starting in 2012. The sampledesign was revised to create a sampleof discharge records from all HCUP-participating hospitals, rather than alldischarge records from a sample ofhospitals. The discharge universe (the.4500 acute care hospitals included inHCUP) was revised to exclude long-termacute care hospitals. The new samplingstrategy produces more precise estimatesthan the previous NIS design by reducingsampling error. Therefore, we chose toanalyze the 2012–2016 NIS data to ensureconsistency and uniformity of the dataduring the study period. The NIS data aremade available yearly, which allows foranalysis of trends over time. The NIS hasbeen used to estimate population-leveltrends in numerous conditions.20–23 The

study involved publicly available deidentifieddata and was thus exempt from review bythe institutional review board.

Study Population

Pyloric stenosis cases were defined asinfants hospitalized for IHPS (InternationalClassification of Diseases, Ninth Revision[ICD-9], and International Classification ofDiseases, 10th Revision [ICD-10], diagnosticcodes 750.5 and Q40.0, respectively),who underwent pyloromyotomy orpyloroplasty before their first birthday(ICD-9 procedure codes 44.3 or 44.2 orICD-10 procedure codes 0DB7, 0DT7, or0D77).24 Pyloromyotomy has been thestandard of care for IHPS in the UnitedStates for decades, but we includedhospitalizations with codes for pyloroplastyto ensure complete identification of allhospitalizations with IHPS. Sample weightsprovided by the NIS for each year wereapplied to generate national-level estimatesof the number of hospitalizations withIHPS.25 Although medical treatment ofIHPS with atropine is practiced in somecountries, it is not the recommendedstandard of care for the management ofIHPS in the United States.26 Thus, any casesof IHPS medically managed were excludedfrom the study. Because each record in theNIS database corresponds to a discharge,infants whose final disposition was codedas transferred out to other short-termfacilities, skilled nursing care, orintermediate care facilities were identifiedby using the “DISPUNIFORM” variable andwere excluded to avoid duplication of thedata at the receiving facility.27 This exclusioncriterion has been used in other studies onneonatal conditions that used the NIS.28,29

Details of the population derivation areshown in Fig 1.

Definition of Variables

Patient-level characteristics such as sex,race, median household income as per zipcode (,$36 000, $36 000–$44 999,.$45 000), primary payer (Medicare orMedicaid, private insurance, self-pay, other),and hospital-level characteristics such ashospital location (rural or urban) andteaching status (rural, urban nonteaching,and urban teaching), hospital bed size(small, medium, and large), and hospital

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region (northeast, Midwest, south, andwest; see Supplemental Fig 3) wereabstracted. Hospitalizations with IHPS weredivided into 2 age groups: neonates(0–28 days old) by using the “AGE_NEONATE”variable and infants (29–364 days old).Neonates were identified by using the“Neomat” variable, which identifies

discharges with neonatal and/or maternaldiagnoses and procedures. To calculate theestimated cost of hospitalization, the NISdata were merged with cost-to-chargeratios available from the HCUP. Weestimated the cost of each inpatient stay bymultiplying the total hospital charge withthe cost-to-charge ratio provided by HCUP.30

The adjusted cost for each year wascalculated in terms of the 2016 cost afteradjusting for inflation according to thelatest consumer price index data releasedby the US government.31 This enabled us tostandardize the costs over the study period.

Outcomes

We analyzed national trends in IHPShospitalizations, costs, and LOS over timeduring the study period. The incidence rateof IHPS was calculated by dividing theweighted number of IHPS hospitalizations bythe number of live births, and this wasreported as the number of IHPShospitalizations per 1000 live births. Thenumber of live births for each year and foreach geographic region and sex wasobtained from the live births data providedby the HCUP in the NIS. Incidence rates forIHPS and their trends over the study periodwere also determined according to race,sex, the expected payer (Medicaid, privateinsurance, etc), and socioeconomic status(SES). Race was categorized as white, non-Hispanic black, Hispanic, Pacific Islander,and others. As defined previously, SES wasdetermined on the basis of the source ofpayment for the admission.32–34 “High SES”included individuals with private insuranceor private health maintenance organizationcoverage, whereas “low SES” consisted ofthose who were self-pay, had Medicaid, orhad no insurance. Resource use wasassessed by using the LOS and the inflation-adjusted total hospital cost for each IHPShospitalization. Median and interquartileranges (IQRs) were used to summarize thedata for LOS and inflation-adjusted hospitalcost because the data were not normallydistributed.

Statistical Analysis

Continuous variables were reported asmedians and IQRs, and categorical variableswere reported as proportions with 95%confidence intervals (CIs). x2 test, t test, oranalysis of variance with post hoc Tukeyhonestly significant difference test formultiple comparisons were used forunadjusted analysis depending on the data.Linear regression was used to determinetrends over time. To assess the variablesthat were associated with IHPS and todetermine the effect of calendar year on the

FIGURE 1 Study population derivation and eligibility flowchart.

FIGURE 2 Temporal trends in the incidence rate of pyloric stenosis in the United States from2012 to 2016.

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incidence rate of IHPS, multivariable logisticregression analysis was performed withsex, age group, race, primary payer,household income, hospital bed size, andhospital location and teaching status ascovariates. The results of this adjustedanalysis are presented as odds ratios (ORs)with 95% CIs. Statistical analyses wereperformed by using SPSS 23.0 (SPSSStatistics, IBM Corporation). A 2-sidedP , .05 was considered significant for allanalyses.

RESULTS

There were 20 808 149 live births over theperiod of 2012–2016, of which 32 450 wereassigned an ICD-9 or ICD-10 diagnosis ofpyloric stenosis. The overall cumulativeincidence rate of IHPS for the studyperiod was 1.56 per 1000 live births. Thedemographic and hospital characteristics ofthe infants hospitalized with IHPS during thestudy period are described in Table 1. Insummary, 82.7% were boys, 53% were ofwhite race, and 94.4% had private (31.1%)or public (63.3) health insurance (Medicareor Medicaid). A majority of thehospitalizations were admitted in large(63.8%) urban teaching hospitals (90.5%).Household income was distributed acrossincome quartiles.

Table 2 reveals the trends in the incidencerate of IHPS hospitalizations in terms of agegroup, sex, race, census region and mode ofpayment as well as resource use (LOS andhospital cost) across the years of the studyperiod. The incidence rate (expressed asper 1000 live births) of IHPS variedsignificantly by age group (infants .neonates; P 5 .001), sex (2.65 in boys vs0.58 in girls; P 5 .001), race (AfricanAmerican patients , Hispanic and whitepatients), SES (1.46 in low SES vs 1.07 inhigh SES; P 5 .004), and census region.These differences were confirmed onmultivariable logistic regression analysis(Table 3).

The overall cumulative incidence rate ofIHPS decreased from 1.76 in 2012 to 1.57 per1000 live births in 2016 (Fig 2), and this wasstatistically significant in adjusted analysis(adjusted OR 0.93; 95% CI 0.92–0.93; seeTable 3). In subgroup analysis, there was asignificant downward trend in the incidence

rate among neonates (0.64–0.48 per1000 live births; P 5 .01) and PacificIslanders (0.42–0.32 per 1000 livebirths;P 5 .02). There were no other trends inthe remaining subgroups during the studyperiod as shown in Table 2. The median LOSwas 2 days (IQR, 2–3 days) and the mediancost of hospitalization was $6078 (IQR,$4695–$8262). There was no significantchange in the LOS and hospital cost duringthe study period.

DISCUSSION

Using the NIS, a nationally representativedatabase, we have reported contemporaryincidence rates and trends in IHPS from2012 to 2016 and examined the resourceuse for the management of IHPS amonginfants in the United States. We havedemonstrated that the cumulative annualincidence rate of IHPS was 1.56 per 1000 livebirths and there was a decrease in thecumulative annual average incidence rate(1.76–1.55) during the study period. Inaddition, we have shown that the LOS andhospital cost for IHPS remained stableduring the study period. The current studyis 1 of the largest analyses on the IHPShospitalizations in the United States,extending our knowledge by examining thetemporal trends in the incidence rate andhealth care resources used for itsmanagement.

The overall cumulative incidence rate of1.56 per 1000 live births is lower than therate of 2.0 per 1000 live births reported byKapoor et al8 using data from population-based birth defects surveillance registriesfrom 11 states in the United States between1999 and 2010. These registries cover 35%of newborn deliveries in the United States,whereas the NIS covers 97% of the USpopulation. The differences between these2 rates may be because of the differentdatabases used for these studies and thedifferent time periods during which thesestudies were conducted. Kapoor et al8 alsonoted that the incidence rate of IHPSdeclined from 2.5 to 1.7 per 1000 live birthsfrom 2006 to 2010. This is consistent withour finding of a declining trend in theincidence of IHPS from 1.76 in 2012 to1.57 per 1000 live births in 2016 for theentire United States. The declining rate of

IHPS has also been reported in otherWestern countries.11,12,35,36 Factors such asyoung maternal age, preterm birth,maternal smoking, bottle-feeding withformula, and macrolide antibiotic exposurein first 2 weeks of life have been stronglyassociated with IHPS.3 Maternal age,20 years is associated with a higher riskof IHPS in some studies, and data from theCenters for Disease Control and Preventionhave revealed a consistent increase in boththe mean maternal age (27.7–28.7 years)and maternal age at first pregnancy(25.4–26.6 years) between 2010 and 2016.37

Concurrent with this decrease, pregnanciesin women,20 years of age has significantlydecreased since 2007.37 Likewise, smokingprevalence among pregnant women andamong women of reproductive age, ingeneral, has fallen in the United States.38,39

Formula feeding is another risk factor forIHPS.5,40 Again, data from the Centers forDisease Control and Prevention reveals thatexclusive breastfeeding rates through thefirst 3 months of age in the United Stateshas been increasing since 2010.41 Exposureto macrolides within the first 3 months oflife is associated with an increased risk ofpyloric stenosis.42 Macrolides are indicatedfor the treatment of pertussis and perinatalchlamydial infections in newborns andinfants. These diseases are on a downwardtrend in the United States, and presumably,prescriptions for and subsequent exposureof newborns to these have also decreasedover time.43–45 In addition, the AffordableCare Act was signed into law in May 2010,greatly expanding medical coverage in theUnited States.46 This massive expansionreally began to go into effect in 2014 withMedicaid expansion. However, it is certainlypossible that increased health carecoverage could have led to better pregnancyplanning and increased early and adequateprenatal care.47 This could have contributedto the decline of IHPS rates in the UnitedStates. Therefore, the reasons for thedeclining incidence rate of IHPS may bemultifactorial.

In terms of age, we observed a decline inthe incidence rate in neonates ,28 days oldbut not in infants. The reasons for thisobserved trend are not clear from thepublished literature, but this observation

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TABLE1

DemographicandHospitalCharacteristicsof

PyloricStenosisHospitalizations

intheUnitedStates

From

2012

to2016

PyloricStenosisHospitalizations

2012

2013

2014

2015

2016

Total

x2P

n5

7400

n5

6520

n5

6065

n5

5995

n5

6470

N5

32450

Sex,%

6SEM

,.001

Male

82.06

0.8

83.76

0.9

82.06

1.0

83.26

1.1

82.76

0.9

82.76

0.4

Female

18.06

0.8

16.36

0.9

18.06

1.0

16.86

1.1

17.36

0.9

17.36

0.4

Race,%

6SEM

,.001

White

54.56

2.5

51.46

2.1

53.76

2.3

52.66

2.3

52.46

2.3

53.06

1.0

AfricanAm

erican

6.86

0.7

7.46

0.8

6.16

0.7

6.06

0.7

7.86

0.8

6.86

0.3

Hispanic

21.86

2.0

23.46

1.9

22.56

2.0

23.16

2.1

24.26

2.1

23.06

0.8

AsianAm

erican

orPacificIslander

1.16

0.3

1.36

0.3

1.26

0.3

1.26

0.3

61.16

0.3

1.26

0.1

Other

6.26

0.7

5.46

0.6

4.86

0.6

6.46

0.8

4.36

0.6

5.56

0.3

Missing

9.56

1.8

11.06

1.8

11.76

2.1

10.86

2.1

10.16

1.8

10.66

0.8

Medianhouseholdincomecategory

forpatient’szip

code,%

(95%

CI)

,.001

0–25th

percentile

32.8(29.0–36.7)

32.3(29.5–35.4)

31.9(28.6–35.5)

31.5(28.3–35.0)

31.7(28.8–34.7)

32.1(30.7–33.5)

26–50th

percentile

27.8(25.2–30.5)

28.6(26.1–31.3)

28.7(26.3–31.1)

27.6(25.1–30.2)

29.6(27.2–32.1)

28.4(27.3–29.5)

51–75th

percentile

23.5(21.4–25.8)

25.2(22.8–27.7)

25.3(22.9–27.9)

23.3(21.1–25.7)

23.2(21.1–25.4)

24.1(23.1–25.1)

76–100thpercentile

15.9(13.5–18.7)

13.9(11.7–16.4)

14.1(11.8–16.8)

17.6(14.9–20.7)

15.5(13.1–18.3)

15.4(14.3–16.5)

Paym

ent,%

(95%

CI)

,.001

Private

31.6(28.9–34.3)

30.0(27.1–32.9)

31.2(28.1–34.4)

31.5(28.9–34.2)

31.4(28.5–34.5)

31.1(29.9–32.4)

Medicare/

orMedicaid

61.1(58.3–63.7)

65.4(62.5–68.1)

63.7(60.5–66.8)

63.1(60.3–65.8)

63.4(60.2–66.5)

63.3(62.0–64.5)

Self-pay

3.1(2.3–4.2)

2.2(1.6–3.1)

2.6(1.9–3.7)

2.8(2.0–3.8)

1.9(1.4–2.8)

2.5(2.2–2.9)

Others

4.3(3.1–5.8)

2.5(1.7–3.6)

2.5(1.7–3.5)

2.7(1.8–3.9)

3.2(2.4–4.4)

3.1(2.6–3.6)

Hospitalcharacteristics,%

(95%

CI)

Hospitallocationandteaching

status

,.001

Rural

2.1(1.2–3.7)

2.2(1.3–3.7)

1.2(0.7–2.1)

0.3(0.2–0.7)

0.8(0.4–1.7)

1.4(1.1–1.6)

Urbannonteaching

10.0(7.7–12.8)

9.7(7.5–12.5)

6.7(4.8–9.2)

7.9(5.6–11.1)

6.0(4.0–9.0)

8.1(7.4–8.9)

Urbanteaching

87.9(84.7–90.5)

88.0(84.9–90.6)

92.1(89.5–94.1)

91.8(88.5–94.1)

93.2(90.2–95.4)

90.5(89.7–91.3)

Hospitalregion,%

(95%

CI)

,.001

Northeast

16.0(11.6–21.6)

15.6(11.2–21.4)

16.1(12.0–21.2)

15.9(11.8–21.1)

14.8(11.1–19.4)

15.7(14.2–17.3)

Midwest

25.0(19.6–31.4)

23.5(18.5–29.4)

23.8(19.0–29.4)

22.0(16.9–28.2)

25.0(19.7–31.2)

23.9(22.2–25.8)

South

40.1(32.7–48.0)

41.9(34.9–49.3)

40.4(33.7–47.4)

41.9(35.4–48.7)

39.6(33.2–46.3)

40.7(38.6–42.9)

West

18.9(14.2–24.7)

18.9(13.9–25.3)

19.8(15.0–25.6)

20.2(15.3–26.1)

20.7(15.9–26.5)

19.7(17.9–21.6)

Bedsize,%

(95%

CI)

,.001

Small

10.8(7.6–15.1)

13.0(8.8–18.6)

13.8(10.0–18.8)

13.7(9.7–18.9)

15.1(11.1–20.3)

13.2(12.1–14.4)

Medium

26.5(20.4–33.7)

20.5(15.4–26.7)

21.9(17.0–27.7)

24.5(19.1–30.8)

21.3(16.0–27.7)

23.0(21.1–25.0)

Large

62.7(55.4–69.4)

66.6(59.6–72.9)

64.3(57.7–70.3)

61.8(55.1–68.1)

63.6(56.9–69.8)

63.8(61.7–65.8)

Baselinedemographicandhospitalcharacteristicsof

hospitalizations

with

IHPS

intheUnitedStates

from

2012

to2016.

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could mean that the age at presentation ofIHPS is increasing. We found no significanttrends with respect to race and ethnicity

(white, African America, and Hispanicpatients), sex, insurance status or SES, andcensus region. However, our finding that the

incidence rate is higher in boys and those ofwhite race is consistent with observationsmade in previous studies.6–8 Authors of few

TABLE 2 Trends in the Incidence and Resource Use for Pyloric Stenosis in the United States (2012–2016)

Year Overall P a P forTrend

2012 2013 2014 2015 2016 2012–2016

Incidence rate of pyloric stenosisb

No. live births 4 195 055 4 143 563 4 162 895 4 177 375 4 129 261 20 808 149 — —

Neonates and infant with pyloric stenosis 7400 6520 6065 5995 6470 32 450 — —

National incidence per 1000 live births 1.76 1.57 1.46 1.43 1.57 1.56 — .24

Incidence according to age group .001

Neonates #28 d old 0.64 0.55 0.53 0.50 0.48 0.54 .01

Infants 29–364 d old 1.12 1.02 0.92 0.93 1.09 1.02 .66

Incidence according to sex .001

Male 3.00 2.71 2.44 2.45 2.66 2.65 .23

Female 0.69 0.55 0.56 0.52 0.58 0.58 .27

Incidence according to racec ,.001

White 1.99 1.72 1.66 1.63 0.177 1.75 .3

African American 0.92 0.9 0.69 0.64 0.93 0.82 .64

Hispanic 2.08 2.0 1.97 1.85 2.09 1.97 .8

Pacific Islander 0.42 0.43 0.36 0.34 0.32 0.37 .02

Other race 1.58 1.28 0.98 1.41 1.02 1.25 .27

Missing race information 1.97 1.73 1.67 1.41 1.54 1.65 .04

Incidence according to payerd ,.01

Medicaid 2.23 2,17 1.98 1.94 2.11 2.09 .27

Private 1.24 1.04 0.99 0.99 1.08 1.07 .31

Self-pay 1.52 0.85 0.82 0.90 0.70 0.94 .12

Other 2.33 1.28 1.27 1.34 1.74 1.61 .51

SES

Low 1.78 1.51 1.32 1.41 1.28 1.46 .004 .05

High 1.23 1.03 0.99 0.99 1.08 1.07 — .31

Incidence according to census regione ,.01

Northeast 1.71 1.51 1.44 1.43 1.44 1.51 .09

Midwest 2.08 1.73 1.64 1.49 1.85 1.76 .39

South 1.85 1.72 1.53 1.54 1.59 1.65 .1

West 1.39 1.23 1.19 1.21 1.35 1.27 .81

Resource use

Median LOS, d (IQR) 2 (2–3) 2 (2–3) 2 (2–3) 2 (2–3) 2 (2–3) 2 (2–3) — .43

Median cost ofhospitalization,US $ (IQR)

5876(4453–8048)

5818(4586–7880)

6031(4681–7938)

6296(4824–8876)

6369(4933–8571)

6078(4695–8262)

— .31

Cost of hospitalization(geometric mean),US $ 6 SEM

6375.3 6 1.0 6325.6 6 1.0 6525.3 6 1.0 7058.3 6 1.0 6974.3 6 1.0 6631.3 6 1.0 — .3

Trends in the incidence rate and resource use in the management of IHPS in the United States from 2012 to 2016. —, not applicable.a P value for student’s t test or analysis of variance as appropriate.b Incidence rate expressed as number of cases per 1000 live births.c White versus Hispanic patients, P 5 .05; White . African American patients, P 5 .001; Hispanic . African American patients, P 5 .001.d Medicaid . private insurance, P 5 .001; Medicaid . self-pay insurance, P 5 .001; other . self-pay insurance, P 5 .01.e Midwest . West, P 5 .001; South . Midwest, P 5 .006; other pairwise comparisons not significant.

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studies have evaluated the associationbetween SES and IHPS, and the results thusfar are conflicting. Using insurance statusas a proxy for SES, we found that IHPShospitalizations with nonprivate insurance(low socio-economic status) had a higherincidence rate. This aligns with 2 previousstudies from the United States in whichauthors demonstrated that low maternaleducational status was associated with ahigher incidence of IHPS.16,18 SES is animportant determinant of pregnancyoutcomes.48 Lower SES is associated withlower mean maternal age at first pregnancyand a higher incidence of smoking duringpregnancy.49,50 Both factors are associatedwith a higher risk of pyloric stenosis asexplained previously. However, Dodge51

reported in a study from Ireland that thathigher social class (defined on the basis ofparental occupation) was associated withhigher odds of IHPS.51 The conflicting result

from this may arise from differences inpatient populations and the definition of SESused.

In our study, we provide unique insights intothe resource use required for themanagement of IHPS at the national level.The median LOS from the current study was2 days, and this is consistent with the LOS of2 to 3 days previously reported.52–55 Themedian estimated cost of care of $6078.30 iscomparable to the cost of $5351 reported inanother population-based study in theUnited States.53 Authors of other studieshave reported hospital charges of $7938 to$11 312.52,54,55 It is instructive to point out thedifferences between hospital charges andhospital costs. The charges are theexpenses incurred by the hospital in takingcare of their patients, and these vary widelyacross hospitals and geographic regions inthe United States.56 Hospital costs areMedicare-allowable costs that the Centers

for Medicare and Medicaid Services hasdetermined to be the costs associated withcare for all patients, not just Medicarepatients.57 The application of the cost-to-charge ratios and the translation of hospitalcharges into actual inflation-adjusted costsin the current study allowed the comparisonof hospital costs for IHPS across years, andthere was no significant change over time.Likewise, there was no significant change inLOS over the study period. These arereassuring in the present era when muchemphasis is being placed on containinghealth care costs in the United States.

The limitations of this study, like allothers conducted by using administrativedatabases, are well described.58

Large databases such as the NIS aresusceptible to coding errors, omissions,and duplications. However, the HCUP hasinstituted mechanisms to ensure the validityof the data in NIS.59 Additionally, IHPS is amajor discharge diagnosis and more likelyto be coded correctly because such codingis related to billing for inpatient hospitalcare. Because surgery is the standard ofcare for IHPS in the United States, validICD-9 and ICD-10 procedure codes forpyloromyotomy and pyloroplasty were usedto identify hospitalizations with IHPS. Codesfor both pyloromyotomy and pyloroplastywere used to identify patients with IHPS toensure complete identification of allhospitalizations with IHPS. However, theoverwhelming standard of treatment of IHPSin the United States is pyloromyotomy;therefore, many of those who were coded ashaving a pyloroplasty may in fact have beendesignated so incorrectly. In addition, thedata used were for discharges rather thanfor individual patients, so data may havebeen represented more than once for anygiven year. Most likely, surgeries were notrepeated; however, readmission for, say,infection and other medical problems mayhave been the culprit. The NIS databasedoes not include clinical information suchas the type of feeding (breast milk orformula feeding) and birth order andmedications such as macrolide exposurebefore the diagnosis of IHPS. Therefore, wecould not directly evaluate whether changesin these were associated with the decline inthe incidence rate of IHPS in this study.

TABLE 3 Adjusted ORs and 95% CIs for the Association Between Selected Infant and HospitalCharacteristics and Pyloric Stenosis in the United States From 2012 to 2016

Variable Adjusted OR (95% CI) P

Year 0.92 (0.91–0.93) ,.001

SES

Low 1.00 (Reference)

High 0.47 (0.46–0.48) ,.001

Sex

Male 1.00 (Reference)

Female 0.22 (0.21–0.23) ,.001

Race

White 1.00 (Reference)

African American 0.29 (0.28–0.31) ,.001

Hispanic 0.85 (0.83–0.88) ,.001

Pacific Islander 0.20 (0.18–0.22) ,.001

Hospital region

Northeast 1.00 (Reference)

Midwest 1.33 (1.28–1.38) ,.001

South 1.26 (1.22–1.30) ,.001

West 0.98 (0.94–1.02) .32

Hospital bed size

Small 1.00 (Reference)

Medium 0.99 (0.96–1.03) .65

Large 1.57 (1.52–1.63) ,.001

Teaching status of hospital

Rural 1.00 (Reference)

Urban nonteaching 2.36 (2.13–2.61) ,.001

Urban teaching 13.77 (12.50–15.12) ,.001

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There appears to be a trend towardlaparoscopic pyloromyotomy, but becausethere is no ICD-9 or ICD-10 code for this, wecould not examine the trends in the type ofIHPS repair and neither were we able toexamine the effect of open versuslaparoscopic repair on LOS and hospitalcost.60 However, a multivariable logisticregression analysis was performed by usingall the relevant data available in the NIS toassess the factors associated with theincidence of IHPS. As with any retrospectiveadministrative data analysis, there is apotential for bias from missing data.However, it is unlikely that the missing datawould have a significant impact on theresults because of the large sample size ofthe current study. Although we classifiedSES according to the expected payer on thebasis of previous studies, this should beinterpreted with caution because thechildren of wealthy parents may be self-paying and thus not of low SES. Finally, westudied the trends in the incidence rate ofIHPS and its associated resource use over a5-year period. It is possible that if we hadincluded the years before 2012, the resultsobtained could have been different.

There are several strengths to our presentstudy. The NIS is the largest all-payerinpatient health care database in the UnitedStates, and it is uniquely equipped tocapture all IHPS hospitalizations across theUnited States irrespective of payer orinsurance status. Previous studies on IHPSin the United States had hitherto useddatabases limited to single states or a fewstates, which may not be nationallyrepresentative.6,8,16-18 Furthermore, the NIS isreleased each year, and this allows for thelongitudinal analysis such as the trends inthe incidence rate of IHPS and its associatedresource use over time. To our knowledge,the current study is the first to providenational-level data on hospital cost for themanagement of IHPS in the United States.

CONCLUSIONS

The cumulative incidence rate of IHPS inthe United States declined from 1.76 to1.57 per 1000 live births between2012 and 2016. The incidence rate ofIHPS varied by race, SES, sex, andgeographic region. The LOS for IHPS

remained low at 2 days without anysignificant change during the study period.Similarly, the cost of hospitalizationremained stable.

Acknowledgments

We acknowledge HCUP, sponsored by theAgency for Healthcare Research and Quality,Rockville, Maryland, and its partnerorganizations that provide data to the HCUP.A list of all HCUP data partners is availableat https://www.hcup-us.ahrq.gov/db/hcupdatapartners.jsp.

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DOI: 10.1542/hpeds.2019-0112 originally published online November 20, 2019; 2019;9;923Hospital Pediatrics 

Amponsah, Parth Bhatt, Matilda Adobea Hesse and Fredrick Dapaah-SiakwanKeyur Donda, Barbara Asare-Afriyie, Marian Ayensu, Mayank Sharma, Jason K.

United States From 2012 to 2016Pyloric Stenosis: National Trends in the Incidence Rate and Resource Use in the

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