Necrotizing Enterocolitis

  • Etiology: combination of immaturity, enteral feeding, ischemia, infection -> mucosal damage -> intestinal ischemia -> necrosis, involves any portion of intestine but distal ileum + proximal colon most common
  • AXR: early (diffusely dilated loops of bowel / ileus, asymmetrically dilated loop of bowel), later (classic triad of pneumatosis intestinalis, portal venous gas, free air), fixed loop can be sign of impending perforation, some perforations (15-20%) can be walled off due to surrounding inflammation and not show free air on AXR, many cases have no AXR findings as some findings of necrotizing enterocolitis on AXR are transient (pneumatosis intestinalis + portal venous gas)
    — Bubbly pneumatosis = submucosal gas, curvilinear pneumatosis = subserosal gas
    — Note: biliary air is more central in liver, portal venous gas is more peripheral in liver
  • US: complicated ascites + free air are signs of perforation, portal venous gas appears as echogenic bubbles in portal veins, pneumatosis intestinalis
  • Complications: strictures in 25%, more common in colon than small bowel, especially in descending colon
  • Clinical: mainly in premature infants: feeding intolerance, abdominal distension, bloody stools, can also affect older stressed infants (after cardiac surgery)
  • Note: stricture should be suspected in an infant with a persistently distended abdomen after treatment for necrotizing enterocolitis


  • Bowel wall thickening (>2.7 mm) or thinning (<1 mm), pneumatosis intestinalis, portal venous gas, ascites, fluid collection, doppler of SMA + celiac trunk – increased peak systolic velocity, hyperemia or no flow, peristalsis, zebra pattern of prominent valvulae conniventes
  • Normal bowel wall -> bowel distension / hyperemia +/- echogenic mucosa -> bowel wall thickening +/- hyperemia, +/- intramural gas +/- loss of gut signature +/- loss of bowel wall distinctness -> bowel wall thinning / bowel distension / bowel contents with debris +/- intramural gas
  • US can help when AXR unremarkable, AXR has paucity of bowel gas or is gasless, AXR shows dilated fixed loop of bowel -> check its perfusion and peristalsis
  • US helpful finding – free air, absent peristalsis, complex ascites, focal fluid collections

Approach to necrotizing enterocolitis:

  • On AXR + US look for 1) gas – intraluminal bowel gas – dilated / pattern, intramural gas, portal venous gas, free gas and 2) calcification – peritoneal, mural, luminal
  • On US look for 1) fluid – free fluid, focal fluid / abscess, intraluminal GI fluid and 2) bowel wall – thickness / echogenicity, peristalsis (real time), perfusion (Doppler)

Radiology Cases of Necrotizing Enterocolitis

Radiology Cases of Diffusely Dilated Loops of Bowel in Necrotizing Enterocolitis

AXR of necrotizing enterocolitis
Supine AXR shows diffusely dilated loops of bowel throughout the abdomen. There is no evidence of pneumatosis intestinalis, portal venous gas, or free air.

Radiology Cases of Pneumatosis Intestinalis in Necrotizing Enterocolitis

AXR of necrotizing enterocolitis
Supine AXR shows linear pneumatosis intestinalis involving several loops of bowel in the left lower quadrant of the abdomen.

Radiology Cases of Portal Venous Gas in Necrotizing Enterocolitis

AXR of necrotizing enterocolitis
Supine AXR shows numerous branching linear lucencies throughout the liver consistent in appearance with portal venous gas.

Radiology Cases of Bowel Perforation in Necrotizing Enterocolitis

Radiology Cases of Bowel Stricture After Necrotizing Enterocolitis

Enema of necrotizing enterocolitis
AP image from an enema shows two fixed strictures in the colon, the first at the junction of the sigmoid colon and descending colon, and the second at the splenic flexure.

Surgery Cases of Necrotizing Enterocolitis

Surgical image of necrotizing enterocolitis
Surgical image shows the bowel was white and necrotic throughout its entire length from the duodenum to the colon. There was no salvageable bowel.