Necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a life-threatening inflammation of the intestinal wall that results in tissue death. It most often affects premature infants. Typical symptoms include abdominal distention, feeding intolerance, rectal bleeding, and lethargy. An x-ray finding of gas within the wall of the intestine (pneumatosis intestinalis) confirms the diagnosis. Management is mainly supportive, involving bowel rest, parenteral nutrition, and antibiotics. Surgery is necessary for severe NEC with intestinal perforation. Mortality rates are high, and surviving infants may develop short bowel syndrome or other long-term complications.

• Hemorrhagic necrotizing inflammation of the intestinal wall
• Most commonly affects the distal ileum and proximal colon

• NEC is the most common cause of acute abdomen in premature infants. ^[1]
• Peak incidence: 2^nd–4^th week after birth ^[2]

Epidemiological data refers to the US, unless otherwise specified.

The causes of necrotizing enterocolitis are not fully understood but multiple factors contribute to the development of the condition. ^[3][4][5][6]

• Intestinal wall perfusion and motility disorders
• Defective or underdeveloped immune system
• Intestinal microbial overgrowth
• Formula feeding
• Rapid increase of enteral nutrition

General features ^[7][8]

• Feeding intolerance
• Abdominal distention
• Abdominal discoloration
• Vomiting
• Rectal bleeding
• Unstable temperature
• Lethargy
• Apnea, bradycardia

Advanced features ^[7][8]

• Stage II (proven NEC)
  • Lack of bowel sounds
  • Abdominal tenderness
  • Cellulitis of the abdominal wall
• Stage III (severe NEC)
  • Generalized peritonitis
  • Significant abdominal tenderness and/or distention
  • Cardiorespiratory instability
• See “Bell staging criteria” for details.

NEC is a clinical diagnosis supported by typical imaging findings; see also “Bell staging criteria” for an overview of clinical and imaging findings by stage.

Imaging ^[9][10]

• Abdominal x-ray: standard imaging modality
  • Pneumatosis intestinalis: pathognomonic finding of gas within the intestinal wall
  • Portal venous gas
  • Radiological signs of bowel obstruction: e.g., bowel dilatation, air-fluid levels
  • Increased intestinal wall thickness
  • Pneumoperitoneum in cases of intestinal perforation
• Abdominal ultrasound: adjunctive imaging modality ^[11]
  • May show intramural, intravenous, and intraperitoneal gas
  • Ultrasound-specific findings include:
    • Reduced or absent peristalsis
    • Increased intestinal wall thickness
    • Decreased intestinal wall perfusion
    • Free intraperitoneal fluid

Laboratory studies ^[8][9]

Laboratory studies can help establish the severity of NEC and guide resuscitation efforts, but they are not diagnostic.

• Basic laboratory studies, blood cultures, and urine cultures should be obtained in all patients.
• Potential findings include:
  • CBC: neutropenia, thrombocytopenia
  • CMP: laboratory findings of hypovolemia
  • Coagulation studies: signs of DIC (see “Diagnosis of DIC”)
  • Blood gas analysis: metabolic acidosis

The differential diagnoses listed here are not exhaustive.

General principles ^[7][9]

• Management is mainly supportive and includes bowel rest, gastric decompression, antibiotics, and parenteral feeding.
• Drainage or laparotomy is required if there is evidence of bowel necrosis.
• All patients with NEC require observation in a neonatal ICU and surgical consultation.

Nonoperative management ^[7][8]

• Initiate cardiovascular (e.g., IV fluids) and respiratory support as needed.
• Stop all enteral feeding and begin parenteral feeding.
• Place a nasogastric suction tube for decompression; use Broselow tape for tube size.
• Initiate broad-spectrum IV antibiotics. ^[7][8][16]
  • There is no preferred antibiotic regimen; follow local protocols and consult a specialist as needed. ^[17]
  • Common regimens include:
    • Ampicillin PLUS gentamicin PLUS metronidazole
    • Piperacillin/tazobactam
    • If MRSA infection is likely: Add vancomycin.
• Provide adequate pain management in children.

Surgical management ^[7][18]

• Indications
  • Absolute: bowel perforation indicated by free intra-abdominal air on x-ray
  • Relative
    • Findings concerning for bowel necrosis (e.g., peritonitis, shock, acidosis)
    • Clinical worsening despite medical therapy
• Procedures
  • Exploratory laparotomy with excision of necrotic bowel and/or enterostomy
  • Primary peritoneal drainage

• ABCDE survey
• Continuous monitoring
• IV fluid resuscitation
• Respiratory support as needed
• Bedside abdominal x-ray or abdominal ultrasound
• Urgent neonatology and pediatric surgery consult
• Discontinue enteral feeding.
• Insert NG tube using Broselow tape.
• Start broad-spectrum IV antibiotics (e.g., regimen of ampicillin, gentamicin, and metronidazole).
• Pain management in children
• Expedite surgery if there is bowel perforation.
• Admit to NICU.

Acute

• Intestinal perforation
• Peritonitis
• Sepsis

Chronic ^[9]

• Short bowel syndrome
• Intestinal stricture
• Intestinal fistula

We list the most important complications. The selection is not exhaustive.

Mortality rate: approx. 10–30% ^[19][20]

• Recommend exclusive breast milk. ^[7][21]
• Other preventative measures for newborns at risk of NEC include: ^[7]
  • Standardized feeding protocols
  • Probiotics
  • Avoidance of acid suppression medication
  • Avoidance of prophylactic antibiotics