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PubMed This is a summary of 12 peer-reviewed journal articles Updated
Neonatology

Diagnostic Tests and Imaging

At a Glance

Necrotizing enterocolitis (NEC) is diagnosed and monitored using abdominal X-rays to look for trapped gas, and ultrasounds to assess live bowel movement and blood flow. Blood tests track markers like platelets and lactate to determine the disease's severity and whether surgery is needed.

When NEC is suspected, the NICU team uses a series of tests to ‘see’ what is happening inside your baby’s abdomen. These tests help them determine the severity of the condition and guide treatment decisions.

Reading the X-Ray

The abdominal X-ray is a traditional gold standard tool used to monitor NEC [1].

  • Pneumatosis Intestinalis: This is a hallmark sign of Definite NEC (Stage II). It occurs when gas-producing bacteria get inside the wall of the intestine, creating a bubbly or soapy pattern on the X-ray [1].
  • Portal Venous Gas: This happens when gas travels from the bowel wall into the veins leading to the liver. It is an independent risk factor for needing early surgery [2]. (Note: Rarely, this can simply be caused by a misplaced umbilical catheter rather than NEC, which doctors will verify) [3][4].
  • Pneumoperitoneum: ‘Free air’ outside the intestines. This indicates a hole (perforation) in the bowel and usually means surgery is urgently required [1].

The Role of Abdominal Ultrasound

While X-rays are standard, many NICUs now use Abdominal Ultrasound (AUS) as a highly sensitive tool for early detection [5][6]. Ultrasound can act like a live video, allowing doctors to measure bowel wall thickness, watch for real-time bowel movement, and use Doppler to check if healthy blood flow is reaching the gut tissue [7][8].

Blood Tests (Biomarkers)

Blood work reveals how your baby’s entire system is handling the stress of the disease [9]:

  • Lactate and Procalcitonin: High levels can indicate poor oxygen delivery to tissues or severe infection, often helping predict the need for surgery [10].
  • Complete Blood Count (CBC): Doctors watch the absolute monocyte count and platelets carefully. A sudden, sharp drop in platelets is a concerning sign of advancing disease [11].
  • I-FABP and TGF-β1: These are specialized biomarkers that indicate specific intestinal cell damage and inflammation, providing earlier clues to severity [9][12].

Common questions in this guide

What does an X-ray show when a baby has NEC?
An abdominal X-ray can show hallmark signs of NEC like pneumatosis intestinalis, which is gas trapped in the bowel wall. It can also reveal free air outside the intestines, indicating a bowel perforation that usually requires urgent surgery.
Why do doctors use ultrasound to check for NEC?
Unlike an X-ray, an ultrasound acts like a live video of the abdomen. It allows doctors to measure bowel wall thickness, watch for natural bowel movements, and use Doppler technology to check if healthy blood flow is reaching the gut tissue.
What do blood tests tell doctors about my baby's NEC?
Blood tests help the medical team see how your baby's entire body is handling the stress of the disease. Doctors track markers like lactate, absolute monocyte counts, and platelets to monitor inflammation and determine if the condition is advancing.
Why are platelets monitored closely during a NEC infection?
A sudden, sharp drop in a baby's platelet count is a concerning sign that the disease may be advancing. It alerts the NICU team that the inflammation and infection are becoming more severe, which helps guide treatment decisions.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Can you show me on the X-ray or ultrasound exactly where the pneumatosis or free air is located?
  2. 2.Are you using abdominal ultrasound to look for bowel movement (peristalsis) and blood flow?
  3. 3.Which specific blood markers (like lactate or platelets) are you tracking most closely to determine if my baby is improving or declining?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (12)
  1. 1

    Application of abdominal sonography in diagnosis of infants with necrotizing enterocolitis.

    Chen S, Hu Y, Liu Q, et al.

    Medicine 2019; (98(28)):e16202 doi:10.1097/MD.0000000000016202.

    PMID: 31305401
  2. 2

    Analysis of early surgical indications and related factors in neonatal necrotizing enterocolitis.

    Shang X, Wang H, Liu Y, et al.

    Frontiers in pediatrics 2025; (13()):1571921 doi:10.3389/fped.2025.1571921.

    PMID: 40464051
  3. 3

    Portal venous gas resulting from umbilical vein catheterization in a very-low-birth-weight infant with no interruption in early feeding.

    Wang J, Yue G, Yang H, et al.

    Pediatric investigation 2021; (5(2)):155-158 doi:10.1002/ped4.12236.

    PMID: 34179714
  4. 4

    Portal gas in neonates; is it always surgical? A case report.

    Altokhais TI

    World journal of clinical cases 2020; (8(17)):3804-3807 doi:10.12998/wjcc.v8.i17.3804.

    PMID: 32953856
  5. 5

    The diagnostic value of abdominal ultrasound in the progression of necrotizing enterocolitis in low-birth-weight neonates.

    Jia L, Li Z, Zhu H, et al.

    Medicine 2025; (104(43)):e45427 doi:10.1097/MD.0000000000045427.

    PMID: 41137361
  6. 6

    Deep learning feature-based model on abdominal radiography outperforms experts for early necrotizing enterocolitis diagnosis in neonates.

    Wu Y, Yang H, Luo X, et al.

    European radiology 2026; doi:10.1007/s00330-025-12264-y.

    PMID: 41528473
  7. 7

    Role of Abdominal US in Diagnosis of NEC.

    Kim JH

    Clinics in perinatology 2019; (46(1)):119-127 doi:10.1016/j.clp.2018.10.006.

    PMID: 30771813
  8. 8

    The role of ultrasound in necrotizing enterocolitis.

    Hwang M, Tierradentro-García LO, Dennis RA, Anupindi SA

    Pediatric radiology 2022; (52(4)):702-715 doi:10.1007/s00247-021-05187-5.

    PMID: 34654968
  9. 9

    Utility of transforming growth factor beta-1 in diagnosis of neonatal necrotizing enterocolitis.

    Almonaem ERA, Almotaleb GSA, Alhameed MHA, El-Shimi OS

    Journal of neonatal-perinatal medicine 2022; (15(4)):795-801 doi:10.3233/NPM-210973.

    PMID: 35811541
  10. 10

    Lactate acid level and prognosis of neonatal necrotizing enterocolitis: a retrospective cohort study based on pediatric-specific critical care database.

    Wang Y, Lai L, Zhang Q, Zheng L

    Jornal de pediatria 2023; (99(3)):278-283 doi:10.1016/j.jped.2022.11.005.

    PMID: 36535423
  11. 11

    Urinary I-FABP, L-FABP, TFF-3, and SAA Can Diagnose and Predict the Disease Course in Necrotizing Enterocolitis at the Early Stage of Disease.

    Coufal S, Kokesova A, Tlaskalova-Hogenova H, et al.

    Journal of immunology research 2020; (2020()):3074313 doi:10.1155/2020/3074313.

    PMID: 32190704
  12. 12

    The Role of Gastrointestinal-Related Fatty Acid-Binding Proteins as Biomarkers in Gastrointestinal Diseases.

    Ho SSC, Keenan JI, Day AS

    Digestive diseases and sciences 2020; (65(2)):376-390 doi:10.1007/s10620-019-05841-x.

    PMID: 31529416

This page explains diagnostic tests for necrotizing enterocolitis for educational purposes. Always consult your NICU team for the interpretation of your baby's specific imaging and blood test results.

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