Necrotising enterocolitis (NEC)b is serious complication in premature babies that is deemed as a surgical emergency. It is one of the most common gastrointestinal issues in premature infants with an incidence of 1-3 per 1000 live births (of which 90% are premature infants). It holds a very high mortality rate of 20-30%.
Pathophysiology
The exact aetiology and pathophysiology is still not known. It is believed to begin with compromised blood supply to the bowel leading to ischaemia. With reperfusion of the bowel reactive oxygen species (ROS) and inflammatory mediators promote an inflammatory response.
In addition, the immature intestinal barrier (due to issues with intercellular junctions) allows bacteria to translocate from the lumen into the wall of the intestine which promotes further inflammation and may lead to tissue damage.
Formula feeding is also implicated as the introduction of foreign proteins and potential pathogenic bacteria may also compromise the intestine and promote inflammation.
It most commonly affects the distal ileum and proximal colon in infants. This is potentially due to the vascular supply of this region being more susceptible to ischaemia-reperfusion injury, along with increased bacterial colonisation and more active digestive processes especially in response to formula feeding.
⚠️ Risk factors
- Prematurity
- Very low birth weight (VLBW) infants - increases risk by 5-10%
- Formula feeding - breastfed babies have a 6-fold lower risk
- Intrauterine growth restriction (IUGR)
- Polycythaemia
- Exchange transfusion
- Hypoxia
- Prolonged antibiotic use
😷 Presentations
- Generally unwell and difficult to settle
- Intolerant to feeding
- Vomiting (may be bilious or blood-stained)
- Abdominal pain and distension
- Haematochezia (passage of fresh blood in the stool)
- Signs of peritonitis:
- Absent bowel sounds
- Sepsis
🔢 Staging
We can use the Bell staging system which stages NEC by the likelihood of NEC diagnosis as well as the signs and symptoms present. It is used to guide management (stage I and II are medically managed while stage III is surgical).
Stage | Diagnosis | Symptoms |
Stage I | Suspected NEC | Lethargy
Distended and shiny abdomen
Gastric retention
Vomiting
Diarrhoea
Rectal bleeding |
Stage II | Proven NEC | Stage I symptoms +
Abdominal tenderness
Visible intestinal loops lacking peristalsis |
Stage III | Advanced NEC | Intestinal perforation
Symptoms of sepsis
Flank redness |
If stage III NEC is left untreated, there will be rapid progression into shock and DIC.
🔍 Investigations
- Bloods
- FBC - neutropenia is associated with a poor prognosis. Thrombocytopenia can be used to assess severity (as if left untreated DIC will develop)
- Blood cultures - to assess any infectious cause.
- CRP & ESR - raised.
- Capillary blood gas - metabolic acidosis.
🏆 Abdominal X-rays are the gold-standard investigation for NEC diagnosis and assessment.
It should be taken AP in the supine position. Additionally, a lateral (from the side with the patient on their back) and lateral decubitus (from the side with the patient on their side).
Signs that point toward a diagnosis of NEC include:
- ⭐️ Intramural gas - also known as pneumatosis intestinalis. This is the hallmark feature of NEC.
- Distended bowel loops
- Thickened bowel wall - seen as the thumbprinting. Thumbprinting represents intestinal oedema.
- Pneumatosis hepatis - gas within the hepatic portal venous system.
- Pneumoperitoneum - may be seen by Rigler sign (which is the whe both sides of the intestinal wall are visible).
🧰 Management
- Antenatal steroids - if a premature delivery is anticipated.
- Breastfeeding
- Probiotics
- Delayed cord clamping
For stages I and II, we can consider conservative management.
Conservative management of NEC includes:
- Maintaining hydration and parenteral feeding
- Stop enteral feeding for 10-14 days - the bowel should also be decompressed with a nasogastric tube.
- Antibiotics - broad spectrum antibiotics are also needed.
For stage III, we can consider surgical management (i.e. if there is perforation, obstruction, sepsis).
- Excision of necrosed bowel
🚨 Complications
- Sepsis
- DIC
- Strictures
- Short-bowel syndrome
- Recurrence of NEC