Necrotising enterocolitis (NEC)

Question 1

Define NEC.

Answer 1

Severe gastrointestinal disease characterised by massive epithelial destruction leading to intestinal barrier failure.

Question 2

What are some risk factors for NEC?

Answer 2

• Prematurity
• Low birthweight
• Formula feeding
• Perinatal stress
• Bacterial colonisation of the intestines
• UAC/UVC insertion
• Congenital heart disease (decreased cardiac output)
• Maternal cocaine use
• Respiratory distress syndrome

Question 3

Explain the aetiology of NEC.

Answer 3

Exact aetiology unknown, likely to be multifactorial. Current hypothesis involves the combination of immature intestinal epithelial barrier and mucosal immune system leading to bacterial translocation with intestinal inflammation. Cycle of localised intestinal mucosal injury leads to infiltration of indigenous bacteria and causes local immunocytes to secrete proinflammatory mediators (chemokines, prostanoids and nitric oxide). This response causes further damage to the intestinal barrier with increased bacterial translocation and therefore increasedd release of proinflammatory mediators. This cycle eventually causes intestinal necrosis/perforation and generalised sepsis.

Question 4

What is Bell’s classification for NEC?

Answer 4

• I: Suspect; non-specific septic signs
• II: Definite; blood investigation derangement and XR changes
• III: Advanced; shock, peritonitis, pneumoperitoneum

Question 5

Summarise the epidemiology of NEC.

Answer 5

0.5% of all live births. 3–5% of infants <1500 g.

Majority of surgical neonatal admissions to neonatal unit.

Question 6

What are signs and symptoms of NEC?

Answer 6

Stage I: Temperature instability, brachycardias and apnoeas, lethargy, poor feeding, bilious (bright green) aspirates, GI bleeding, mild ileus on XR.

Stage II: As above, with metabolic acidosis, thrombocytopenia, increased GI bleeding, abdominal tenderness, abdominal wall erythema, possible mass, definite AXR signs.

Stage III: As above, with shock, inotropic support, neutropenia, DIC, generalised peritonitis, marked abdominal distension, pneumoperitoneum on AXR.

Question 7

What are appropriate investigations for NEC?

Answer 7

Bloods: Depends on stage; Hb down, reduced platelets, high WCC, metabolic acidosis, electrolyte derangement, coagulopathy.

AXR: Pneumatosis intestinalis, ileus, portal venous gas, persistent ‘fixed’ dilated loops of bowel or pneumoperitoneum ‘football sign’ (in the supine position, air collects anterior to the abdominal viscera, the falciform ligament is also outlined).

USS: Operator dependent but may visualise intramural gas and the presence of NEC mass.

Question 8

What is the management for NEC?

Answer 8

Conservative: NBM, NGT decompression, IV broad-spec Abx (gram -/+ cover), blood and plantelet transfusions, electrolyte imbalances correction

Surgical: Resection of necrotic bowel with formation of a stoma and mucous fistula/primary anastomosis. Extensive disease may be left as balance of resection versus short gutsyndrome.

Question 9

What are complications associated with NEC?

Answer 9

• Strictures
• Fistulas
• Short gut syndrome
• Malabsorption
• TPN associated cholestasis and enterocyst formation

Question 10

What is the prognosis of NEC?

Answer 10

20 – 40% of neonates require surgery.

Up to half of those die.