Necrotizing enterocolitis (NEC)

Question 1

What is Necrotizing Enterocolitis (NEC)?

Answer 1

NEC is a bacteria-mediated inflammatory condition of the neonatal bowel that leads to sepsis and bowel necrosis.

Question 2

Why is NEC significant in neonates?

Answer 2

NEC is the most common cause of peritonitis in neonates and a major cause of morbidity and mortality.

Question 3

How common is NEC?

Answer 3

It occurs in 1 in 1000 live births and affects up to 10% of very low birth weight (VLBW) infants (<1500g).

Question 4

What is the most important risk factor for NEC?

Answer 4

Prematurity – 90% of affected neonates are preterm.

Question 5

What causes NEC?

Answer 5

NEC is due to an uncontrolled inflammatory response to pathogenic bacteria in the gut lumen, occurring in the setting of an immature immune system.

Question 6

What is the most important risk factor for NEC?

Answer 6

Prematurity – 90% of affected neonates are preterm.

Question 7

How does lack of human breast milk contribute to NEC?

Answer 7

Breast milk provides protective factors, including antibodies and beneficial bacteria that help strengthen gut immunity. Formula feeding lacks these benefits, increasing NEC risk.

Question 8

How does NEC lead to sepsis and bowel necrosis?

Answer 8

Bacteria breach the gut mucosal barrier, enter circulation, and trigger sepsis and coagulative necrosis of the gut.

Question 9

What maternal conditions increase the risk of NEC?

Answer 9

Maternal diabetes, chorioamnionitis, HIV (neonatal infection), and fluid overload.

Question 10

How does maternal diabetes contribute to NEC?

Answer 10

Hyperglycemia and vascular dysfunction increase fetal inflammation and gut immaturity.

Question 11

Why does lack of antenatal steroids increase NEC risk?

Answer 11

Antenatal steroids promote lung and gut maturity; without them, preterm neonates have weaker gut barriers.

Question 12

How can NEC risk be reduced antenatally?

Answer 12

Antenatal care, maternal steroids if <34 weeks, HIV treatment (PMTCT/ HAART), and conservative IV fluids.

Question 13

What conditions cause perinatal ischaemia, increasing NEC risk?

Answer 13

Pre-eclampsia, maternal vasoactive drug use (cocaine, opiates), hypoxic-ischaemic encephalopathy (HIE), PDA, and blood transfusion.

Question 14

Why does a patent ductus arteriosus (PDA) increase NEC risk?

Answer 14

Steals blood flow from the gut, causing gut hypoxia and necrosis.

Question 15

How can perinatal ischaemia-related NEC be prevented?

Answer 15

Good obstetric care, avoiding NSAIDs for PDA, pausing feeds during blood transfusions, and using erythropoietin instead of transfusions when possible.

Question 16

How does an altered microbiome contribute to NEC?

Answer 16

Pathogenic Gram-negative bacteria overgrowth damages the gut and increases inflammation.

Question 17

What factors disrupt the neonatal microbiome?

Answer 17

NICU bacterial outbreaks, formula feeding, rapid feed escalation, prolonged antibiotic use, and perinatal sepsis.

Question 18

How can NEC be prevented through microbiome protection?

Answer 18

Hand hygiene, exclusive breast milk feeding, kangaroo mother care, safe formula prep, and use of probiotics/prebiotics.

Question 19

What triggers inflammation in NEC?

Answer 19

Pathogenic gut bacteria trigger an uncontrolled inflammatory response in the immature gut.

Question 20

What happens to the gut barrier?

Answer 20

Increased permeability → Bacteria invade → Coagulative necrosis of bowel wall

Question 21

How does NEC lead to bowel perforation?

Answer 21

Full-thickness necrosis → Bowel wall weakens → Perforation in 15-50%

Question 22

Which part of the bowel is most affected?

Answer 22

Terminal ileum & ascending colon (vascular compromise may contribute)

Question 23

Why is NEC so deadly?

Answer 23

Bacterial translocation → Sepsis + Pro-inflammatory cytokine storm → Multi-organ failure

Question 24

What is the mortality rate?

Answer 24

30-50% (higher if perforation and septic shock occur)

Question 25

How does SIP (spontaneous intestinal perforation) differ from NEC?

Answer 25

Most common in extremely low birth weight babies (<1000g) ✅ Absence of metabolic acidosis or inflammatory signs ✅ No pneumatosis intestinalis or bowel thickening on x-rays ✅ Prognosis slightly better than NEC

Question 26

What causes bowel obstruction in neonates?

Answer 26

✅ Volvulus (twisting of the intestine), adhesive bands (post-op), incarcerated inguinal hernia ✅ Presents with bilious vomiting & abdominal distension

Question 27

How is GERD different from NEC?

Answer 27

✅ Non-bilious vomiting & apnoea ✅ Typically resolves with conservative management

Question 28

What other infections may present with ileus and non-specific sepsis signs?

Answer 28

✅ Pneumonia, meningitis, or urinary tract infection ✅ Need to rule out with clinical signs and cultures

Question 29

What are some causes of bloody stools or vomiting in neonates?

Answer 29

✅ Cows-milk protein allergy, maternal swallowed blood, midgut volvulus ✅ Differentiate based on history and clinical presentation

Question 30

What are the DDx of NEC

Answer 30

1. Spontaneous intestinal perforation 2. Bowel obstruction 3. GERD 4. Pneumonia, meningitis, UTI 5. Allergy due to cows milk protein allergy, maternal swallowed blood and midgut volvulus

Question 31

When do premature neonates typically present with NEC?

Answer 31

First week of life ✅ 2-3 weeks after birth in some cases

Question 32

When do term neonates usually present with NEC?

Answer 32

✅ 10% of cases present within 2-3 days after birth ✅ Often with a history of infectious, hypoxic, or metabolic insults

Question 33

What are the early features of NEC?

Answer 33

✅ Subtle and can be difficult to differentiate from other neonatal sepsis causes ✅ Fulminant progression: Can lead to death within 24 hours of symptom onset in over 1/3 of affected infants

Question 34

What are the risk factors for a poor outcome?

Answer 34

✅ Diffuse patchy or multiple areas of small bowel necrosis ✅ Pan-involvement (over 75% of bowel involvement)

Question 35

What might a discoloured abdominal wall indicate in extremely low birth weight neonates?

Answer 35

Bowel perforation ✅ Common in infants <1000g birth weight ✅ Pneumoperitoneum (air in the peritoneum) from bowel perforation

Question 36

What is the clinical significance of a discoloured abdominal wall?

Answer 36

✅ Discolouration (often blue or reddish) may indicate peritonitis or subcutaneous emphysema from air escaping into the abdominal wall ✅ Signs of sepsis and abdominal distension usually accompany bowel perforation

Question 37

How can bowel perforation in such a baby be differentiated from other conditions?

Answer 37

✅ X-ray findings: Look for pneumoperitoneum (free air) ✅ Absence of pneumatosis intestinalis or bowel thickening (in contrast to NEC)

Question 38

What is the prognosis in bowel perforation in extremely low birth weight babies?

Answer 38

✅ Slightly better prognosis than NEC, but remains a serious condition ✅ Immediate surgical intervention is often required to manage perforation and prevent further complications

Question 39

What are the clinical features of Stage I (Suspected NEC)?

Answer 39

Non-specific signs of sepsis, such as temperature instability, glucose instability, and apnoea. Non-specific signs of ileus, including abdominal distension, increased gastric residual volumes (aspirated before orogastric tube feeds), milk/bilious vomiting, and faecal occult blood.

Question 40

What are the radiological features (AXR) of Stage I (Suspected NEC)?

Answer 40

Non-specific bowel distension and thickening.

Question 41

What are the management principles for Stage I (Suspected NEC)?

Answer 41

- Bowel rest (gastric tube drainage, nil per mouth). - Treat sepsis with broad-spectrum antibiotics. - Administer intravenous fluids. - Provide high-care monitoring of vital signs. - Monitor electrolytes carefully and blood cell counts

Question 42

What are the clinical features of Stage IIa (Definite NEC - early)?

Answer 42

Specific features of gastrointestinal sepsis, including bloody stool/vomitus, progressive distension, absent bowel sounds, abdominal tenderness, and palpable bowel loops.

Question 43

What are the radiological features (AXR) of Stage IIa (Definite NEC - early)?

Answer 43

Pneumatosis intestinalis (air in the bowel wall). Tubular thickened bowel loops.

Question 44

What is the management for Stage IIa (Definite NEC - early)?

Answer 44

As per Stage I: Bowel rest (gastric tube drainage, nil per mouth), treat sepsis with broad-spectrum antibiotics, intravenous fluids, high-care monitoring of vital signs, and electrolyte monitoring.

Question 45

What are the clinical features of Stage IIb (Definite NEC - moderate)?

Answer 45

As Stage IIa, with additional alterations in haemodynamic status (e.g., tachycardia). Thrombocytopaenia, hyponatraemia, and mild acidosis.

Question 46

What are the radiological features (AXR) of Stage IIb (Definite NEC - moderate)?

Answer 46

Ascites

Question 47

What is the management for Stage IIb (Definite NEC - moderate)?

Answer 47

As per Stage IIa, but with intensive care monitoring, support, and surgical consultation.

Question 48

What are the clinical features of Stage IIIa (Severe NEC with organ dysfunction)?

Answer 48

Deteriorating vital signs, including septic shock with organ dysfunction, hypotension, apnoea, disseminated intravascular coagulopathy (DIC), progressive metabolic acidosis, peritonitis, and a tender mass (usually in the right iliac fossa) from sealed-off bowel perforation.

Question 49

What are the radiological features (AXR) of Stage IIIa (Severe NEC with organ dysfunction)?

Answer 49

White-out of the abdomen (ascites). Persistent fixed loop of bowel for >24 hours.

Question 50

What is the management for Stage IIIa (Severe NEC with organ dysfunction)?

Answer 50

As per Stage IIb, with multisystem support such as ventilation, inotropes. Consider paracentesis of ascites (look for bacteria or "prune juice" of necrotic bowel). Possible surgical exploration to exclude dead bowel.

Question 51

What are the clinical features of Stage IIIb (Severe NEC with perforation)?

Answer 51

As per Stage IIIa, with additional features including frank peritonitis. May have oedema, redness, and blue-black discolouration of the abdominal wall. Hyperkalaemia and refractory metabolic acidosis.

Question 52

What are the radiological features (AXR) of Stage IIIb (Severe NEC with perforation)?

Answer 52

Pneumoperitoneum (often best visualized on lateral shoot-through X-ray). Rigler’s sign, football sign, liver lucency, etc.

Question 53

What is the management for Stage IIIb (Severe NEC with perforation)?

Answer 53

As per Stage IIIa, but with surgery, including peritoneal drainage and/or laparotomy.

Question 54

What can an AP abdominal film, aided by a lateral shoot-through, reveal in cases of NEC?

Answer 54

- Tubular distension of bowel loops. - Thickened loops of bowel and free fluid, causing bowel loops to be displaced from each other. - Pneumatosis intestinalis (gas within the bowel wall). - Portal vein gas outlining the portal veins in the liver. -The gas is hydrogen produced by bacteria in the bowel wall.

Question 55

What is Pneumatosis intestinalis, and how can it be identified on radiology?

Answer 55

Pneumatosis intestinalis is gas within the bowel wall. It can be submucosal ("soapy bubbles") or intermuscular with a linear configuration ("tram-track": black line between white lines). In older children, it may mimic the appearance of stool, but faecal loading should not normally be seen in a child on milk feeds.

Question 56

What radiological features can be seen in the liver related to NEC?

Answer 56

Liver lucency and outlining of the falciform ligament with gas create the "football" sign.

Question 57

What is Pneumoperitoneum, and how is it visualized on X-ray?

Answer 57

Pneumoperitoneum is the presence of air in the peritoneal cavity. It may be seen on lateral shoot-through X-ray. "Rigler’s sign" is a feature of pneumoperitoneum, where gas outlines both sides of the bowel wall.

Question 58

In which stages of NEC is surgical intervention required, and what is the rate of surgery in these cases?

Answer 58

Surgical intervention is required in all Stage 3b cases and many Stage 3a cases. Surgery occurs in 30 to 50% of cases, although lower rates are reported in highly developed, high-income settings.

Question 59

What is the role of initial peritoneal drainage in NEC management

Answer 59

Initial peritoneal drainage may help release abdominal compartment syndrome. In selected extremely low birth weight (ELBW) babies, peritoneal drainage might be the only intervention required, as the underlying small, spontaneous perforation may seal off without further intervention in a third of ELBW babies.

Question 60

What are the goals of surgery once the baby has stabilized in Stage 3a or 3b NEC?

Answer 60

- Confirmation of bowel viability. - Resection of necrotic bowel. - Evacuation of stool from the peritoneal cavity in the case of perforation with soiling. - Re-establishment of intestinal continuity, which may involve staging with an initial stoma in the case of diseased distal bowel or damage-control surgery in very sick infants. - Preservation of bowel length if intestinal recovery is expected.

Question 61

When is stoma reversal feasible in infants with NEC, and what needs to be excluded before reversal?

Answer 61

Stoma reversal is often feasible 4-6 weeks after surgery in thriving infants. Before reversal, distal bowel strictures due to fibrosis from partial bowel necrosis should be excluded by contrast enema.

Question 62

What are some common complications associated with stoma formation in NEC?

Answer 62

30% stoma problems including: High output Prolapse Stenosis Anastomotic leak at reversal

Question 63

What are the common wound complications after NEC surgery?

Answer 63

10-25% wound problems, including: Wound breakdown Infection

Question 64

What intestinal complications can arise after NEC?

Answer 64

10% intestinal strictures following surgery.

Question 65

What are the long-term neurological outcomes for babies with NEC?

Answer 65

Poor long-term neurological outcomes are common: - 30-50% of babies with NEC experience brain injury and developmental delay. - This is often associated with prolonged intensive care and poor nutritional intake (especially in babies with short bowel syndrome or high output stomas). - As many as 50% may experience permanent neurological damage, including severe cerebral palsy. - Normal neurodevelopment is seen in less than a quarter of survivors.

Question 66

What is the mortality rate for babies with NEC, and what factors influence it?

Answer 66

Mortality rates: - 15% in high-income settings. - 30-50% in middle-income settings. - Up to 90% in low-income settings. Lower gestational age is associated with higher mortality.