Paediatrics

Necrotising Enterocolitis

Necrotising enterocolitis (NEC) is acquired ischaemic and inflammatory necrosis of the immature neonatal bowel, in which bacterial gas tracks into the bowel wall and portal veins and necrosis perforates.

In a nutshell

Necrotising enterocolitis (NEC) is acquired bowel necrosis in a neonate, mostly babies born before 32 weeks or below 1500 g. Stop feeds, decompress the stomach, alert the neonatal surgical centre and start the local intravenous neonatal regimen with anaerobic cover within 1 hour.

Classic presentation

A baby born at 26 weeks, now 3 weeks old and on full feeds, develops abdominal distension, bloody stool and apnoea, and the film shows pneumatosis intestinalis.

Key points

Age at onset falls as gestation rises: about 20 days below 30 weeks, 14 days at 31 to 33 weeks, 5 days beyond 34 weeks.
Term NEC appears in the first days of life and points to duct-dependent heart disease, asphyxia, polycythaemia or growth restriction with absent end-diastolic flow.
About 5 to 6% of babies born before 32 weeks develop NEC. In a national English study 46.5% of those with severe NEC died.
About a quarter of survivors develop an intestinal stricture, usually colonic, from 2 months and as late as 20 months afterwards.
Short bowel syndrome follows roughly 9% of cases, and prolonged parenteral nutrition then risks cholestasis and liver failure.
NG195 also advises prophylactic oral nystatin during antibiotics for babies up to 1500 g or born before 30 weeks (1.26.1). It gives no dose.
No NICE guideline covers NEC itself. NG195 covers neonatal antibiotics only; staging and feeding intervals come from trust and network guidelines.

First-line investigation

Supine abdominal radiograph plus a left lateral decubitus film. Pneumatosis intestinalis makes NEC definite; free air means perforation.

Management

Stop feeds, decompress, treat

Stop all enteral feeds and pass a nasogastric or orogastric tube on free drainage. Send blood culture, FBC, CRP, gas, lactate, glucose, electrolytes and coagulation.^4,3
Start the locally selected narrow-spectrum neonatal regimen within 1 hour. NICE gives intravenous flucloxacillin plus gentamicin as an example; add anaerobic cover such as metronidazole for suspected NEC (NG195 1.15.2 and 1.23.1).³
Take every neonatal dose and interval from the current BNF for Children and local antimicrobial policy. NG195 does not define one universal late-onset NEC dose schedule.³
Start parenteral nutrition through a central line. Expect large losses into the abdomen and anticipate ventilation as the abdomen distends.⁴

Image, stage and monitor

Supine film plus left lateral decubitus, or a cross-table lateral if the baby is too unstable to turn. Pneumatosis makes NEC definite; free air means perforation.^4,2
Repeat films at least every 24 hours while the baby is sick or deteriorating. A single normal film excludes nothing.^4,2
Modified Bell: IA and IB suspected (IB has frank rectal blood), IIA and IIB definite, IIIA critically ill with intact bowel, IIIB perforated.⁴
If gentamicin is used, measure its trough immediately before the second dose. Aim below 2 mg/litre, and below 1 mg/litre beyond three doses (NG195 1.35.1 and 1.35.4).³

When the surgeons take over

Discuss established or deteriorating NEC with the neonatal surgical centre before perforation is proven, and transfer from modified Bell stage IIIA.⁴
Pneumoperitoneum is the only absolute indication to operate. Transfer urgently for it, for fixed dilated loops, or for failure of medical treatment.^4,2
Relative indications: abdominal wall erythema, palpable mass, portal venous gas, refractory acidosis or thrombocytopenia, and a rising inotrope requirement.^2,4
Cot-side peritoneal drainage or laparotomy is the neonatal surgeon's decision. Drainage is used first below 1000 g, and most drained babies still need laparotomy.²

Rest the gut, then rebuild feeding

Bowel rest by stage: 3 days nil by mouth and antibiotics for Bell I, a minimum of 7 days for Bell II and III (Royal Cornwall trust guideline).⁴
NG195 gives 7 days of antibiotics for a positive blood culture and supports longer where the site of infection is NEC (1.25.1).³
Restart on the neonatal team's decision using a high-risk regimen. Mother's own milk first; donor human milk rather than formula halves NEC risk.^5,7
Contrast study before stoma closure, or sooner if feeding intolerance returns, because about a quarter of survivors form a stricture.²

Exam traps

The NICE NG253 sepsis figures are for people aged 16 or over. Do not bring 250 mL boluses or NEWS2 into a neonatal answer.
The first film can be normal. Pneumatosis and free air are intermittent, so one clear radiograph never excludes NEC.
A neonate cannot stand for an erect film. Free air is sought on a left lateral decubitus or a cross-table lateral view.
Probiotics reduce NEC in very preterm infants but show little or no effect in extremely preterm or extremely low birth weight babies.
Bile-stained aspirates or raised gastric residuals alone neither diagnose NEC nor justify stopping feeds.
Spontaneous intestinal perforation is a different disease: earlier, smaller baby, no pneumatosis, and excluded from the national NEC audit definition.
Most preterm NEC starts after 72 hours and follows the late-onset infection pathway. The empirical regimen is selected locally from resistance data; flucloxacillin plus gentamicin is a NICE example, not a universal rule.

Illustrations

Pneumatosis intestinalis on abdominal radiographA neonatal abdominal radiograph showing intramural gas with dilated bowel loops, labelled as a highly suggestive sign of NEC rather than an isolated substitute for clinical assessment.RadsWiki, Wikimedia Commons · CC-BY-SA-3.0

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.