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PubMed This is a summary of 23 peer-reviewed journal articles Updated
Pediatric Surgery

Anatomy and Types of Small Bowel Atresia

At a Glance

Small bowel atresia is a birth defect where a baby's intestine is completely blocked or severely narrowed. Duodenal atresia happens early in pregnancy and is often linked to Down syndrome, while jejunoileal atresia occurs later due to a loss of blood flow to the bowel.

Learning that your newborn has an intestinal blockage can be overwhelming. Small bowel atresia occurs when a portion of the small intestine does not form correctly, resulting in a complete blockage (atresia) or a significant narrowing (stenosis) [1].

Doctors categorize these blockages based on where they are located and how they formed. It is important to remember that these “types” are anatomical descriptions used by surgeons to plan the best repair; they are not “stages” like those used in cancer and do not necessarily predict the overall health of your child [2][3].

Duodenal Atresia: An Embryological Error

The duodenum is the first part of the small intestine, located just after the stomach. Blockages here usually happen very early in pregnancy (around weeks 8 to 10) [1][4].

  • How it happens: During early development, the duodenum starts as a solid tube of cells. Normally, it hollows out (recanalizes) to create a path for food. If this process is interrupted, a blockage remains [1][5].
  • Annular Pancreas: Sometimes, the pancreas (an organ that helps with digestion) forms in a ring shape around the duodenum, squeezing it shut from the outside [6].
  • Genetic Links: About 30% to 40% of babies born with duodenal atresia also have Trisomy 21 (Down syndrome) [7][8]. Because of this link, doctors often recommend genetic screening and heart ultrasounds for these infants [9][10].

Jejunoileal Atresia: A Vascular Event

The jejunum and ileum make up the middle and end sections of the small intestine. Unlike duodenal blockages, these usually happen later in pregnancy due to a “vascular accident” [11][12].

  • How it happens: A sudden loss of blood flow to a segment of the intestine (often caused by a twist or a small blood clot) causes that section to wither away and disappear before birth [11][13].
  • Cystic Fibrosis Link: In some cases, a baby with Cystic Fibrosis develops very thick, sticky first stool called meconium ileus. This thick stool can block the bowel and cause a twist or a loss of blood flow, leading to atresia [14][15].

The Grosfeld Classification System

Surgeons use the Grosfeld Classification to describe the exact shape and severity of jejunoileal atresias [2][16].

Type Description Key Feature
Type I Mucosal Web An internal wall or “web” blocks the tube, but the outside of the bowel looks continuous [2].
Type II Fibrous Cord The two ends of the bowel are separated but connected by a thin, solid string of tissue [17].
Type IIIa Mesenteric Gap The two ends are completely separated with a V-shaped gap in the mesentery (the tissue that carries blood to the gut) [2].
Type IIIb Apple Peel Also called “Christmas Tree” atresia. The end of the bowel is missing its usual blood supply and coils around a single artery like a spiral [18][19].
Type IV String of Sausages Multiple separate blockages occur in a row, making the bowel look like a string of links [20][21].

Understanding which type your baby has helps the surgical team determine how much healthy intestine is available and what the feeding plan will look like after recovery [22][23].

Common questions in this guide

What is the difference between duodenal and jejunoileal atresia?
Duodenal atresia occurs in the first part of the small intestine, usually early in pregnancy due to a development error. Jejunoileal atresia happens in the middle or lower sections, typically later in pregnancy due to a sudden loss of blood flow to the developing bowel.
What does the Grosfeld Classification mean for my baby?
The Grosfeld Classification is a system surgeons use to describe the exact shape and severity of jejunoileal blockages. Knowing whether your baby has Type I, II, III, or IV helps the surgical team plan the best repair and estimate how much healthy intestine is available.
Is small bowel atresia linked to other genetic conditions?
Yes, about 30% to 40% of babies with duodenal atresia also have Trisomy 21 (Down syndrome). Additionally, some cases of jejunoileal atresia are associated with Cystic Fibrosis, which can cause thick stool that blocks the bowel before birth.
What is 'apple peel' or Type IIIb atresia?
'Apple peel' atresia, or Type IIIb, is a specific type of blockage where the end of the bowel is missing its usual blood supply. Instead of lying normally, the intestine coils around a single artery, resembling a spiral or an apple peel.
Will my baby need other tests if diagnosed with duodenal atresia?
Because duodenal atresia is often linked to other conditions like Down syndrome, doctors typically recommend genetic screening. They will also likely order imaging, such as a heart or kidney ultrasound, to check for any associated developmental differences.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What is the specific Grosfeld type (I, II, IIIa, IIIb, or IV) of my baby's atresia?
  2. 2.Was the blockage in the duodenum caused by an intrinsic problem with the bowel wall or something outside like an annular pancreas?
  3. 3.Has my baby been screened for associated conditions like Trisomy 21 (Down syndrome) or Cystic Fibrosis?
  4. 4.Was there any evidence of 'meconium ileus' (thick, sticky stool) found during the surgery?
  5. 5.How much healthy small intestine was left after the repair, and is the ileocecal valve still in place?
  6. 6.Will my baby need any additional imaging, such as a heart or kidney ultrasound, to check for other common associations?

Questions For You

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References

References (23)
  1. 1

    Congenital duodenal obstruction - Advances in diagnosis, surgical management, and associated controversies.

    Patterson KN, Cruz S, Nwomeh BC, Diefenbach KA

    Seminars in pediatric surgery 2022; (31(1)):151140 doi:10.1016/j.sempedsurg.2022.151140.

    PMID: 35305801
  2. 2

    A new variant of type III jejunoileal atresia.

    Dao DT, Demehri FR, Barnewolt CE, Buchmiller TL

    Journal of pediatric surgery 2019; (54(6)):1257-1260 doi:10.1016/j.jpedsurg.2019.02.003.

    PMID: 30827488
  3. 3

    [Surgical management of duodenal atresia due to annular pancreas and intestinal atresia IIIb].

    López-Díaz NG, Oliver-García EF, Núñez-Enríquez JC

    Revista medica del Instituto Mexicano del Seguro Social 2023; (61(1)):123-129.

    PMID: 36542807
  4. 4

    Delayed Diagnosis of Congenital Duodenal Stenosis in a 16-Year-Old Girl.

    Velmishi V, Alushani D, Dervishi E, et al.

    Case reports in medicine 2024; (2024()):1070253 doi:10.1155/2024/1070253.

    PMID: 38736458
  5. 5

    Delayed Presentation of Duodenal Atresia in a Male With Trisomy 21.

    Sega AG, Meckmongkol T, Westmoreland T

    Cureus 2022; (14(1)):e21700 doi:10.7759/cureus.21700.

    PMID: 35237490
  6. 6

    Associated congenital anomalies among cases with Down syndrome.

    Stoll C, Dott B, Alembik Y, Roth MP

    European journal of medical genetics 2015; (58(12)):674-80.

    PMID: 26578241
  7. 7

    Congenital Duodenal Obstruction in Neonates: Over 13 Years' Experience from a Single Centre.

    Kumar P, Kumar C, Pandey PR, Sarin YK

    Journal of neonatal surgery 2016; (5(4)):50 doi:10.21699/jns.v5i4.461.

    PMID: 27896158
  8. 8

    Chromosomal Abnormalities and Pregnancy Outcomes for Fetuses With Gastrointestinal Tract Obstructions.

    Wu X, Su L, Shen Q, et al.

    Frontiers in pediatrics 2022; (10()):918130 doi:10.3389/fped.2022.918130.

    PMID: 35783302
  9. 9

    Association of Duodenal Atresia, Malrotation, and Atrial Septal Defect in a Down-Syndrome Patient.

    Angotti R, Molinaro F, Sica M, et al.

    APSP journal of case reports 2016; (7(2)):16.

    PMID: 27170921
  10. 10

    Clinical significance of prenatal double bubble sign on perinatal outcome and literature review.

    Demirci O, Eriç Özdemir M, Kumru P, Celayir A

    The journal of maternal-fetal & neonatal medicine : the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians 2022; (35(10)):1841-1847 doi:10.1080/14767058.2021.1874338.

    PMID: 33455511
  11. 11

    Histomorphological Features of Intestinal Atresia and its Clinical Correlation.

    Subbarayan D, Singh M, Khurana N, Sathish A

    Journal of clinical and diagnostic research : JCDR 2015; (9(11)):EC26-9 doi:10.7860/JCDR/2015/13320.6838.

    PMID: 26674207
  12. 12

    Type I Jejunal Atresia in Identical Twins: A Rare Occurrence.

    Salimi A, Nia SR, Eftekhari SS, et al.

    Journal of neonatal surgery 2017; (6(3)):68 doi:10.21699/jns.v6i3.616.

    PMID: 28920028
  13. 13

    Congenital intestinal atresia associated with a mesenteric cystic lymphangioma in a low birth weight neonate: A case report.

    Fukuta A, Inoue T, Kawakubo N, et al.

    International journal of surgery case reports 2020; (75()):136-139 doi:10.1016/j.ijscr.2020.09.021.

    PMID: 32949911
  14. 14

    Proximal small bowel obstruction in a patient with cystic fibrosis: a case report.

    Alattar Z, Thornley C, Behbahaninia M, Sisley A

    Surgical case reports 2019; (5(1)):143 doi:10.1186/s40792-019-0701-y.

    PMID: 31520190
  15. 15

    Meconium Ileus.

    Waldhausen JHT, Richards M

    Clinics in colon and rectal surgery 2018; (31(2)):121-126 doi:10.1055/s-0037-1609027.

    PMID: 29487495
  16. 16

    Jejunoileal Atresia in a Newborn: Our Experience From Northern Tanzania and Literature Review.

    Goodluck G, Gnanamuttupulle M, Sadiq A, et al.

    Clinical medicine insights. Pediatrics 2022; (16()):11795565221075313 doi:10.1177/11795565221075313.

    PMID: 35221742
  17. 17

    An Atypical Variant of Apple Peel Atresia: Reporting a Rare Case.

    Bin Arif T, Ahmed J, Malik F, et al.

    Cureus 2019; (11(11)):e6047 doi:10.7759/cureus.6047.

    PMID: 31819834
  18. 18

    Christmas tree pattern ileal atresia with intestinal malrotation in a 15-day-old infant: A rare dual congenital anomaly in the pediatric population - A case report.

    Shadrack M, Mbaga MR, Christopher S, et al.

    International journal of surgery case reports 2025; (136()):111948 doi:10.1016/j.ijscr.2025.111948.

    PMID: 40976031
  19. 19

    The role of preserved bowel and mesentery fixation in apple-peel intestinal atresia.

    Han J, Hao Z, Wang L, et al.

    BMC pediatrics 2022; (22(1)):407 doi:10.1186/s12887-022-03475-z.

    PMID: 35820908
  20. 20

    Jejunal Atresia With a Rare Association: A Case Report and Literature Review.

    Qumsieh O, Qawasmeh L, Jaradat R, et al.

    Cureus 2024; (16(4)):e58141 doi:10.7759/cureus.58141.

    PMID: 38741810
  21. 21

    Situs inversus abdominalis, polysplenia, complex jejunal atresia and malrotation in a neonate: A rare association.

    Chinya A, Naranje K, Mandelia A

    International journal of surgery case reports 2019; (56()):93-95 doi:10.1016/j.ijscr.2019.02.016.

    PMID: 30861494
  22. 22

    Management and Outcomes of Jejunoileal Atresia Within the United Kingdom.

    Bethell GS, Hughes B, Varik RS, et al.

    Journal of pediatric surgery 2025; (60(7)):162334 doi:10.1016/j.jpedsurg.2025.162334.

    PMID: 40268118
  23. 23

    Treatment of jejunoileal atresia by primary anastomosis or enterostomy: Double the operations, double the risk of complications.

    Eeftinck Schattenkerk LD, Backes M, de Jonge WJ, et al.

    Journal of pediatric surgery 2022; (57(9)):49-54 doi:10.1016/j.jpedsurg.2021.07.021.

    PMID: 34429189

This page explains the anatomical types of small bowel atresia for educational purposes. Always consult your pediatric surgeon or neonatologist regarding your baby's specific diagnosis, classification, and surgical plan.

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