Necrotizing enterocolitis (NEC) is a disease that primarily affects premature infants, where portions of the intestine undergo necrosis and tissue death. It is the most common and lethal gastrointestinal disease affecting premature neonates. A 12-day old premature male infant presented with lethargy, hypothermia, feeding intolerance, bilious vomiting and bloody diarrhea. Physical exam revealed abdominal distension, loops of bowel visible in the abdomen, abdominal wall erythema and absent bowel sounds. NEC ranges from mild cases involving feeding intolerance to severe cases involving intestinal necrosis, perforation and septic shock. Risk factors include prematurity, low birth weight, initiation of feeding and bacterial infection. Diagnosis involves clinical and

1. NECROTIZING
ENTEROCOLITIS (NEC)
LEOR ARBEL, MS-3

2. CLINICAL VIGNETTE
A 12-day-old male born at 33 weeks becomes lethargic and hypothermic
over the course of 24 h. He is not tolerating his formula feeds, has two
episodes of bilious emesis, and has three episodes of bloody diarrhea.
Physical exam reveals abdominal distention, visible loops of bowel,
abdominal wall erythema, and absent bowel sounds.

3. EPIDEMIOLOGY
• Most frequent & lethal disorder affecting intestines of preterm neonate
• Occurs in ~6-7% of very low birth weight infants (< 1500 grams)
• May be seen in term infants too, but typically these infants have a preexisting illness (eg
congenital heart disease, sepsis)
• Incidence decreases with increasing gestational age and birth weight
• Overall mortality: 10-50%
• Depends on severity of illness & amount of bowel removed
• Predicted that NEC will soon surpass neonatal respiratory distress syndrome as
principal cause of death in preterm infants

4. RISK FACTORS
• Prematurity (>95% of cases)
• Birthweight ≤ 1,500 grams
• Initiation of enteral feeding
• Bacterial infection (may be an inciting or a permissive factor)
• Intestinal ischemia associated with asphyxia at birth

5. CLINICAL FEATURES
• MC involved sites: (1) terminal ileum (2) colon
• Gross findings: Bowel distension with patchy areas of thinning,
pneumatosis, gangrene or frank perforation
• Microscopic findings: “Bland infarct” with full-thickness necrosis

6. CLINICAL MANIFESTATIONS
• Abdominal distension
• Bloody stools/rectal bleeding
• Pneumatosis intestinalis
• Bilious emesis
• Absent bowel sounds
• Abdominal tenderness/redness
• Nonspecific signs (temp instability,
apnea/bradycardia, lethargy, hypotension)
Note: Actual spectrum of disease ranges from mild cases of feeding intolerance and
abdominal distension to severe cases characterized by intestinal necrosis, perforation
and septic shock.

7. ABDOMINAL RADIOGRAPH FINDINGS
Image Source:
Brunicardi FC, Andersen DK,
Billiar TR, Dunn DL, Hunter JG,
Matthews JB, Pollock RE. Figure
39-19 in Schwartz’s Principles of
Surgery, 10e, 2014.
Abdominal radiograph of
infant with necrotizing
enterocolitis. Arrows point
to area of pneumatosis
intestinalis (small gas
bubbles in bowel wall)
Other Radiographic
Findings in NEC
• Non-specific bowel
dilatation
• Thickening of bowel
wall
• Fixed, dilated loop
(unchanged on >1
radiograph)
• Portal venous gas
• Free intraperitoneal
gas (indicates
intestinal
perforation)

8. ABDOMINAL RADIOGRAPH FINDINGS
Source:
UpToDate.
Radiograph of
necrotizing
enterocolitis in
premature
infants.

9. LAB FINDINGS
• Low platelet count
• Metabolic acidosis (poor
prognostic sign)
• Heme-positive stool
• Abnormally ↑ or ↓ WBC
• Left shift of WBC
• Neutropenia
• Evidence of DIC

10. BELL’S STAGING CRITERIA
CLINICAL RADIOGRAPHIC MANAGEMENT
SUSPECTED
NEC
• Mild abd distension
• Poor feeding
• Emesis
• Mild ileus • Medical
• Work up for
sepsis
DEFINITE NEC • Same as Suspected
PLUS marked abd
distension
• Bloody stools
• Significant ileus
• Pneumatosis intestinalis
• Portal venous gas
• Medical
ADVANCED
NEC
• Same as Definite
PLUS unstable vital
signs
• Septic Shock
• Pneumatosis intestinalis
• Pneumoperitoneum
(“football sign” indicates
severe disruption of
intestinal barrier – ie
bowel perforation)
• Surgical

11. DDX
• Infectious Enterocolitis (eg Campylobacter, C. difficile, Salmonella, Shigella)
• Spontaneous Intestinal Perforation (no pneumatosis intestinalis, occurs within 1st
week of life, independent of feeding)
• Anal Fissures
• Cow’s Milk Protein Allergy (rare in preterm infants, rarely seen < 6 wks old, symptoms
resolve after changing feeds to protein hydrolysate or crystalline amino acid formula)
• Intestinal obstruction secondary to anatomic/functional condition (eg Hirschsprung
disease, ileal atresia, volvulus, meconium ileus)

12. MEDICAL MANAGEMENT – SUSPECTED NEC
- Make pt NPO
- Get baseline KUB
- Test all stool for occult blood
- CBC, platelets & blood culture
- Urine culture & CSF is systemic
signs present
- Maintenance IVF
- Serial abdominal examinations
- Consider gastric decompression,
abx, stool culture
- Observe closely for worsening
- If improvement occurs, consider
cautious feeding in 3 days

13. MEDICAL MANAGEMENT –
DEFINITE/ADVANCED NEC
• NPO for 7-10 days
• IVF (due to “third spacing”, fluid resuscitation
to improve bowel perfusion may be needed →
eg D5-lactated ringers at 150 ml/kg per 24 hr)
• Monitor urine output closely
• Gastric decompression
• Serial abdominal radiographs to check for
perforation (AP & cross table lateral q6-8hr)
• Endotracheal intubation/assisted ventilation
(as needed)
• Circulatory support (volume expanders,
dopamine)
• Blood culture & antibiotics (amp & gent for 7-
10 days)*
• Follow CBC/platelets/PT/PTT/fibrinogen
• Measure arterial pH and blood gas tensions
• Correct metabolic acidosis
• Monitor electrolytes (watch for hyperkalemia!)
*Anaerobic coverage usu not needed unless
infant if several wks old

14. SURGICAL CONSIDERATIONS
• Operative intervention is indicated when there is evidence of:
• Bowel perforation
• Necrotic bowel (fixed loop, metabolic acidosis, DIC, shock)
• Progressively worsening clinical condition despite appropriate medical mgmt
• For neonates with PDA who develop NEC, begin medical mgmt. Consider
urgent operative closure of the PDA, since indomethacin cannot be given to
an infant with suspected or definite NEC!
• Peritoneal drain may be utilized in extremely ill infants to delay/avoid laparotomy

15. COMPLICATIONS
• Intestinal Stricture → Bowel obstruction
• Short Bowel Syndrome
• Cholestasis (if prolonged dependence on TPN)

16. REFERENCES
• Schanler, RJ. Clinical features and diagnosis of necrotizing enterocolitis in
newborns. In: UpToDate, Post TW (Ed), UpToDate, Waltham, MA. (Accessed
on February 27, 2017.)
• Hackam DJ, Grikscheit T, Wang K, Upperman JS, Ford HR. Pediatric
Surgery. In: Brunicardi F, Andersen DK, Billiar TR, Dunn DL, Hunter JG,
Matthews JB, Pollock RE. Eds. Schwartz's Principles Of Surgery, 10e. New
York, NY: McGraw-Hill; 2015.
Http://Accessmedicine.Mhmedical.Com/Content.Aspx?Bookid=980&sectio
nid=59610881. Accessed February 27, 2017.
• UCSF Children’s Hospital. Necrotizing Enterocolitis. Intensive Care Nursery
House Staff Manual. 2004. The Regents of the University of California.