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Ministry of Health

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Published: 29/11/2011

Modified Bell Staging

Definite NEC

NEC with Portal Venous Gas

Suspicious (but not) NEC

Necrotising enterocolitis (NEC) is a severe disease of the intestinal tract, typically involving small and/or large bowel. Diagnosis is made with a combination of clinical features and radiographic findings, although sometimes a firm diagnosis may not be made until laparotomy. The cause is unclear but is probably related to a complex interplay between intestinal ischaemia, injury, and infection. The incidence is inversely proportional to gestational age, and the risk of developing NEC continues longer in smaller infants. Other infants at risk include asphyxiated infants, infants following cardiac surgery, and following exchange transfusion. It is rare in infants who have not been enterally fed.

The incidence in infants <32 weeks is in the region of 5-10%, depending on the diagnostic criteria used. The survival for infants with non-surgical NEC is good, whereas up to 50% of infants who require laparotomy may die. Extensive resection of bowel may be associated with short bowel syndrome.

Modified Bell Staging

Modified from: Walsh MC, Kliegman RM. Necrotizing enterocolitis: treatment based on staging criteria. Pediatr Clin North Am 1986; 33:179:

Modified Bell Staging	Classification	Systemic Signs	Abdominal Signs	Radiological Signs
I A	Suspected NEC	Temperature instability Apnoea Bradycardia Lethargy	Aspirates Mild abdominal distension Positive faecal occult blood	Normal Mild intestinal dilatation Mild ileus
I B	Suspected NEC	As above	Fresh blood PR	As above
II A	Proven NEC - mildly ill	As above	As above, plus Absent bowel sounds +/- abdo tenderness	Intestinal dilatation Ileus Pneumatosis intestinalis
II B	Proven NEC - moderately ill	As above, plus mild metabolic acidosis mild thrombocytopenia	As above, plus absent bowel sounds definite tenderness +/- abdominal cellulitis RLQ mass	As above, plus Portal vein gas +/- ascites
III A	Advanced NEC - severely ill, bowel intact	As above, plus Hypotension Bradycardia Severe apnoea	As above, plus Signs of generalised peritonitis Marked tenderness Marked distension	As above, plus Definite ascites
III B	Advanced NEC - severely ill, bowel perforated	As above	As above	As above, plus Pneumoperitoneum

Definite Radiographic NEC

	These radiographs demonstrate the classic intramural gas (pneumatosis intestinalis) appearance of necrotising enterocolitis (NEC). Lucency within the bowel wall is seen throughout the abdomen. In this supine view, no free intraperitoneal air is seen but a lateral decubitus view is necessary to exclude a bowel perforation. The intramural gas may show as thin lines within the bowel wall, or as a series of coalesced "cysts".

NEC with Portal Venous Gas

	Portal venous gas may be seen if gas produced by organisms in the intestinal wall tracks through into the portal circulation. It can be a subtle finding.
	In the image to the left, there is extensive pneumatosis involving several areas of the bowel. There is distension of the stomach. There is also lucency in the liver, representing portal venous gas.

Suspicious but not NEC

	Sometimes the diagnosis of NEC can be difficult to make on both clinical and radiological grounds. In this circumstance, repeating the radiographs may help in establishing diagnostic certainty. Occasionally, faecal loading of the large bowel may have appearances of NEC.
	This initial film demonstrates a suspicious area in the right upper quadrant. The baby had no clinical signs suggestive of NEC but had passed a small amount of rectal blood.
	On a film the following day, there appeared to be cystic abnormalities of the bowel in a similar area. The baby remained well, with no changes on the full blood count, no abdominal distension or signs, and no bileous aspirates. He was however commenced on treatment for NEC on the basis of suspicion about the radiological findings.
	He then passed a large bowel motion. A follow-up film was reassuringly normal and, in the absence of any significant clinical or haematological indicators of NEC, treatment was stopped at 48 hours. He remained clinically well and tolerated full oral feeds without incident.