Radiological presentation
Classic abdominal radiography remains the primary diagnostic method for NEC. Key diagnostic findings include:
- Intestinal pneumatosis: dilated bowel loops with characteristic gas bubbles directly within the thickness of the bowel wall are visualized.
- Pneumoperitoneum: with the development of perforation, free gas in the abdominal cavity can be extensive. A specific sign is gas outlining the falciform ligament (falciform ligament).
- Portal venous gas (Portal venous gas): on the radiograph, it is determined as linear areas of radiolucency projected over the upper left quadrant of the abdomen. This is because in newborns, the liver is relatively large, occupies the entire transverse diameter of the abdominal cavity, and gas accumulation is often visualized precisely in the left lobe.
Ultrasound findings
Ultrasound examination (US) allows a more detailed assessment of the bowel wall condition and the presence of complications:
- Pneumatosis: manifests as bowel wall thickening. Characteristic echogenic foci are detected in its upper (independent / non-dependent) part.
- Portal venous gas: multiple echogenic inclusions are visible on transverse liver scans. They often have a linear shape and spread toward the periphery of the organ.
- Interloop fluid: the appearance of accumulations of echogenic fluid between dilated bowel loops indicates the progression of the process and is considered a poor prognostic sign.
Late complications and surgical management
One of the main late complications of NEC is the formation of strictures, which develop in nearly 33% of surviving infants.
Surgical treatment often requires stoma creation. Subsequently, prior to reconstructive surgery (performing an anastomosis on the previously diverted bowel), a contrast radiographic examination is mandatory. A water-soluble contrast agent is used, administered either antegrade through the distal end of the stoma or as an enema. The goal of the study is an accurate assessment of the caliber and patency of the distal gastrointestinal tract.
Differential diagnosis: causes of neonatal obstruction
NEC often needs to be differentiated from other causes of progressive abdominal distension and delayed passage of meconium (normally, meconium passes within the first 24–48 hours). Supine radiography shows multiple dilated loops, but distinguishing the small intestine from the large intestine in newborns is difficult due to identical caliber and indistinct haustra.
The main alternative causes of obstruction include:
- Hirschsprung disease: a neurocristopathy caused by the absence of ganglion cells in the Auerbach and Meissner plexuses. It manifests as a paradoxical narrowing of the rectum. The most formidable complication is Hirschsprung-associated enterocolitis (occurring in 18–50% of patients), which presents with severe diarrhea and sepsis and is a leading cause of death. A contrast enema reveals an inverted rectosigmoid index (normally >1, in the disease <1).
- Intra-abdominal lymphatic malformation: a thin-walled, multilocular cystic formation in the mesentery or omentum. It can serve as a fulcrum (fulcrum) for the development of small bowel volvulus.
- Megacystis-microcolon-intestinal hypoperistalsis syndrome (Berdon syndrome): a rare pathology affecting females. It is characterized by massive enlargement of the urinary bladder, a flabby abdomen, and microcolon. Mortality reaches 80%.
- Functional immaturity of the colon and meconium plug syndrome.
Briefly: answers to topical questions
What radiographic signs are detected in Hirschsprung disease on a contrast enema?
During a contrast enema in patients with Hirschsprung disease, specific changes are revealed, depending on the length of the aganglionic segment.
- Narrowing of the rectum — accompanied by a cone-shaped transition zone to the proximally dilated ganglionic bowel.
- Irregular contractions — determined in the denervated rectum.
- Inversion of the rectosigmoid index (rectosigmoid ratio) — in short-segment disease, the ratio becomes <1 (normally >1).
- Shortening of the colon — in total agangliosis, the bowel has a normal caliber but is shortened, with smoothing of the contours of the hepatic and splenic flexures.
In newborns, radiographic signs may be absent, as time is required for the ganglionic bowel to dilate.
Class and exam questions
What ultrasound observation is considered a poor prognostic sign in NEC?
The presence of accumulations of echogenic fluid between bowel loops (interloop fluid).
Why is a contrast study performed before stoma closure after NEC?
To assess the caliber of the distal gastrointestinal tract and rule out strictures, which develop in 33% of patients.
What else to study on this topic
- Technique of performing a contrast enema in newborns
- Hirschsprung disease: classification and diagnostic imaging
- Berdon syndrome (megacystis-microcolon-intestinal hypoperistalsis syndrome)
- Intra-abdominal lymphatic malformations
- Causes of delayed meconium passage in term and preterm infants
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