When a premature baby’s belly becomes swollen and feedings stop being tolerated, one of the first things the NICU team does is order an abdominal X-ray. For many parents, that film — and the radiologist’s report a few lines long that follows it — is the moment necrotizing enterocolitis (NEC) goes from a worry to a diagnosis. Later, if that family looks into a cow’s-milk-based formula case, those same images become some of the most important pages in the entire medical record.
This article explains, in plain English, what NEC actually looks like on an X-ray: the specific findings radiologists search for, what each one means about how sick a baby is, how those findings line up with the staging system doctors use, and why the imaging record is so central both to the diagnosis and to a legal case. It is written for parents, not radiologists — but it uses the real terms you will see in the chart so you can read them with understanding.
The one-sentence version. The finding that most strongly points to NEC on an X-ray is pneumatosis intestinalis — gas trapped inside the wall of the bowel itself — and as the disease worsens the films may also show gas in the portal vein or free air outside the intestine, each of which tells doctors, and later a legal team, how severe the NEC became.
What does NEC look like on an X-ray?
On a plain abdominal X-ray, NEC most often appears as pneumatosis intestinalis — fine bubbly or thin, curved streaks of gas sitting inside the wall of the intestine rather than in the normal open space within it. In a premature infant with belly signs, radiologists treat that finding as the hallmark, or pathognomonic, sign of NEC. More advanced disease can add gas in the portal vein or free air in the abdomen, which signals a perforation.
The reason a radiologist can be so confident with pneumatosis is that healthy bowel gas stays inside the intestinal channel. When gas instead appears within the wall of the loops — produced as bacteria invade injured, inflamed tissue — that is abnormal in a way that, in the right clinical setting, is essentially unique to NEC. That is what “pathognomonic” means: a finding so characteristic that its presence, alongside the baby’s symptoms, confirms the diagnosis.
The three findings that matter most
NEC imaging comes down to three key findings, in rough order of severity. Understanding them helps parents make sense of both the radiology report and the treatment decisions that follow.
Pneumatosis intestinalis
Gas inside the bowel wall, seen as bubbly or linear, curved streaks tracing the loops. In a preemie with feeding intolerance, this is the finding that confirms definite NEC.
Portal venous gas
Gas from the bowel wall carried into the portal vein toward the liver, appearing as branching dark lines over the liver. It generally marks more extensive, more severe NEC.
Pneumoperitoneum (free air)
Air that has escaped outside the bowel into the abdominal cavity — the sign of a perforation. This is the finding that most often triggers emergency surgery.
Free air can be subtle, so radiologists look for specific patterns that reveal it: the “football sign” (a large oval of lucency over the abdomen outlined by the falciform ligament), Rigler’s sign (gas visible on both the inside and outside of the bowel wall, making the wall itself stand out), and free air rising to the highest point of the belly on a side-lying or horizontal-beam view. Each is a way of catching a perforation that a single, straight-on film might miss.
Why the same films that diagnose NEC also grade its severity
Neonatologists classify NEC using the modified Bell’s staging criteria, first described by Dr. Martin Bell and colleagues in 1978 and refined by Walsh and Kliegman in 1986. That system combines a baby’s clinical signs with the X-ray findings — which is exactly why the radiology record carries so much weight. The imaging is not a side note; it is built into the definition of the disease and its stage.
| Modified Bell stage | What it means | Typical X-ray findings |
|---|---|---|
| Stage I — Suspected | Nonspecific signs; NEC is on the list but not confirmed. | Normal gas pattern, mild ileus, or dilated loops — nothing specific. |
| Stage IIA — Definite, mildly ill | NEC is now confirmed. | Pneumatosis intestinalis present. |
| Stage IIB — Definite, moderately ill | Confirmed NEC with more systemic involvement. | Pneumatosis plus portal venous gas, sometimes with ascites (fluid). |
| Stage IIIA — Advanced, severely ill | Critically ill; bowel not yet perforated. | Definite NEC with ascites; no free air. |
| Stage IIIB — Advanced, perforated | The bowel has perforated — a surgical emergency. | Pneumoperitoneum (free air outside the bowel). |
Reading down that table, the progression is clear: the X-ray does not just answer whether a baby has NEC, it helps answer how severe it is — and severity drives everything from whether surgery is needed to the long-term outlook. For a fuller walk-through of the staging system, see our explainer on Bell staging of NEC, and for what the medical-versus-surgical line means, our piece on surgical NEC vs. medical NEC.
How the X-rays are actually taken
When NEC is suspected, a NICU does not usually take one film and stop. The standard approach is serial abdominal radiographs — often repeated every six hours in a baby thought to be developing NEC — so the team can watch the bowel gas pattern change over time and catch a perforation early. A finding that is missing at 2 a.m. can appear on the film taken at 8 a.m., and the sequence itself becomes part of the story.
Two views do most of the work:
- The supine AP film (KUB). The standard flat-on-the-back view of the “kidneys, ureters, and bladder” region — really the whole abdomen — used to assess the bowel gas pattern and to spot pneumatosis and portal venous gas.
- A cross-table lateral or left lateral decubitus film. A horizontal-beam view taken with the baby lying still or turned onto the left side. Because free air rises, these views are the most sensitive way to detect even a tiny pocket of air from a perforation that a straight-on film can hide.
In many centers, ultrasound is now used alongside the plain films, because it can sometimes show bowel-wall gas, portal venous gas, or fluid before or more clearly than an X-ray. But the plain radiograph remains the backbone of NEC imaging, and it is what most parents will find referenced in the chart.
“In these cases, the imaging record is often the most objective evidence there is,” says Alex Alvarez, Managing Partner of The Alvarez Law Firm and a Board Certified Civil Trial Lawyer. “A radiologist read that film in real time, during the baby’s care, with no lawsuit in mind — and wrote down what they saw. When a report documents pneumatosis on a specific date and time, that is a fixed, contemporaneous fact. It tells us the diagnosis was real, when it was recognized, and how far it progressed. We build the timeline of a case around records like that, not around anyone’s memory of what happened years later.”
What if the X-ray was “normal” or the films are missing?
A single normal-looking film does not rule NEC out. Early NEC frequently shows only nonspecific findings — dilated loops, a sluggish or fixed gas pattern, or even a strikingly gasless abdomen — and pneumatosis can be transient, visible on one image and resolved on the next. This is precisely why serial films and the overall clinical picture matter more than any one snapshot. A diagnosis of NEC is made from the whole sequence, not a lone image.
It also means the complete imaging record is important. Radiology in the NICU generates the films themselves, the radiologist’s dictated reports, and often preliminary reads noted by the bedside team — and these do not always say exactly the same thing. Requesting the full set, including the actual images and every report, is part of understanding what really happened. Our guide to reading a NICU progress note walks through how these entries fit together and how to request the complete record under HIPAA.
“When I review a file, I read the films and the reports side by side, in order,” says Herb Borroto, M.D., J.D., the firm’s Medical-Legal Expert. “I want to see when the first abnormal film appeared, whether pneumatosis or portal venous gas was documented, whether serial films were actually obtained on the schedule the standard of care calls for, and whether free air ever showed up. The radiology tells you not only that a baby had NEC, but how the disease moved — and whether the response to it kept pace. That sequence is medicine, and in these cases it is also the backbone of the timeline.”
This is general information, not medical or legal advice. X-ray findings are interpreted by physicians in the context of each baby’s full clinical picture, and imaging can be subtle or change quickly. Nothing here diagnoses any child or predicts the outcome of any case. Past results do not guarantee future outcomes; every case is evaluated on its own facts and its own records.
How The Alvarez Law Firm uses the imaging record
When we review a potential NEC formula case, the abdominal films and radiology reports are among the first records we obtain. We are confirming the objective facts: that NEC was documented, which findings appeared and when, how the disease progressed under modified Bell staging, and whether surgery followed. Alongside the imaging, we confirm the eligibility basics — how premature the baby was and whether a cow’s-milk-based formula or fortifier was fed. Our team, led by Board Certified Civil Trial Lawyer Alex Alvarez and supported by Medical-Legal Expert Herb Borroto, M.D., J.D., handles that record-gathering so families do not have to piece it together alone.
Free, confidential case review. No fees unless we recover compensation for you.
- Learn the warning signs: Signs of NEC in premature babies.
- Understand severity: Bell staging of NEC.
- Read the record: Reading a NICU progress note.
- See if your family qualifies: Do I qualify for an NEC lawsuit?
Frequently asked questions
What does NEC look like on an X-ray?
On an abdominal X-ray, NEC most often shows as pneumatosis intestinalis — thin bands or bubbles of gas trapped inside the wall of the bowel itself, rather than in the normal space inside the intestine. Radiologists treat pneumatosis intestinalis in a premature infant as the hallmark, or pathognomonic, sign of NEC. More advanced disease can show gas in the portal vein (portal venous gas) or free air outside the bowel (pneumoperitoneum), which signals a perforation.
What is pneumatosis intestinalis?
Pneumatosis intestinalis is gas within the wall of the intestine. In a premature baby with feeding intolerance and belly signs, it is the radiographic finding that confirms definite NEC — modified Bell stage II. It appears on the film as fine bubbly or linear, curved streaks following the loops of bowel. Because it is considered the pathognomonic sign of NEC, its presence in the record is often the single most important imaging fact in a baby’s chart.
Does a normal X-ray mean my baby did not have NEC?
Not necessarily. Early NEC can show only nonspecific findings such as dilated bowel loops or a gasless abdomen, and pneumatosis can be transient — visible on one film and gone on the next. That is why NICUs obtain serial X-rays, often every six hours, when NEC is suspected. A diagnosis rests on the whole clinical picture and the full sequence of films, not a single image, which is one reason the complete imaging record matters so much.
Why do the X-rays matter in an NEC lawsuit?
The abdominal films are objective, time-stamped evidence created during care. They document whether NEC was present, how severe it became under modified Bell staging, and when key findings such as pneumatosis or free air first appeared. Because these images are read and reported by radiologists in real time, they are central to confirming the diagnosis, establishing severity, and building the medical timeline in a cow’s-milk-formula NEC case.
Sources
- Bell MJ, Ternberg JL, Feigin RD, et al. “Neonatal necrotizing enterocolitis: therapeutic decisions based upon clinical staging.” Annals of Surgery, 1978 — the original Bell staging criteria.
- Walsh MC, Kliegman RM. “Necrotizing enterocolitis: treatment based on staging criteria.” Pediatric Clinics of North America, 1986 — the modified Bell staging system.
- Medscape / eMedicine — Necrotizing Enterocolitis Imaging and Workup (radiographic findings, KUB and cross-table lateral views, serial radiography). emedicine.medscape.com
- Radiopaedia — Necrotising enterocolitis (pneumatosis intestinalis and portal venous gas as pathognomonic findings; pneumoperitoneum). radiopaedia.org
- The Radiology Assistant — Necrotizing Enterocolitis (imaging signs, portal venous gas, free-air detection). radiologyassistant.nl
- Johns Hopkins All Children’s Hospital — Clinical pathway: Evaluation and Management of Suspected, Medical and Surgical Necrotizing Enterocolitis (2022). hopkinsmedicine.org