Overview
Definition:
Necrotizing enterocolitis (NEC) is a serious and potentially life-threatening inflammatory condition of the gastrointestinal tract, predominantly affecting premature infants
It is characterized by bowel wall inflammation, leading to ischemia, necrosis, and potentially perforation of the intestine.
Epidemiology:
NEC is the most common gastrointestinal emergency in neonates, occurring in approximately 1-5% of all NICU admissions and up to 10% of premature infants weighing less than 1500 grams
The incidence is inversely proportional to gestational age and birth weight
It is more common in male infants and those exclusively formula-fed.
Clinical Significance:
NEC is a leading cause of mortality and morbidity in neonates
Survivors often face long-term complications including short bowel syndrome, neurodevelopmental deficits, and increased risk of recurrent NEC
Early recognition and appropriate management are critical to improving outcomes and reducing mortality.
Clinical Presentation
Symptoms:
Abdominal distension and tenderness
Vomiting, often bilious
Hematochezia (bloody stools)
Lethargy and irritability
Apnea and bradycardia
Poor feeding tolerance
Temperature instability (hypo- or hyperthermia).
Signs:
Overtly distended, tense, and erythematous abdomen
Palpable abdominal mass
Absent bowel sounds or generalized decreased bowel sounds
Gastric residual increases
Signs of shock: hypotension, poor perfusion, oliguria.
Diagnostic Criteria:
Clinical signs and symptoms combined with radiographic evidence of pneumatosis intestinalis are key for diagnosis
The modified Bell staging criteria are widely used to classify the severity of NEC: Stage I (suspected NEC), Stage II (definite NEC), and Stage III (advanced NEC)
Specific findings for each stage are detailed in management sections.
Diagnostic Approach
History Taking:
Gestational age and birth weight are paramount
Feeding history (breast milk vs
formula, advancement)
History of asphyxia or other perinatal insults
Previous episodes of NEC or sepsis
Maternal risk factors.
Physical Examination:
Thorough abdominal examination for distension, tenderness, erythema, rigidity, and masses
Assess hydration status, perfusion, and vital signs (temperature, heart rate, respiratory rate, blood pressure)
Monitor for signs of sepsis and shock.
Investigations:
Abdominal X-rays are essential: initial supine and cross-table lateral views
Look for pneumatosis intestinalis (linear lucencies in the bowel wall), portal venous gas, free air in the abdomen (pneumoperitoneum), dilated bowel loops, and thickening of bowel wall
Complete blood count with differential (leukocytosis or leukopenia, thrombocytopenia)
Blood cultures if sepsis is suspected
Electrolytes, BUN, creatinine to assess hydration and renal function
Lactate levels to assess tissue perfusion and severity
Coagulation profile if surgery is considered.
Differential Diagnosis:
Intestinal obstruction (malrotation, atresia)
Sepsis
Hirschsprung disease
Intussusception
Volvulus
Meconium ileus
Feeding intolerance.
Management
Initial Management:
Immediate cessation of oral feeding
Nasogastric tube decompression to relieve distension
Intravenous fluid resuscitation to maintain hydration and perfusion
Broad-spectrum antibiotics to cover common enteric pathogens
Correction of coagulopathy
Frequent monitoring of vital signs and abdominal girth.
Medical Management:
For Bell Stage I and II NEC: Conservative management is initiated
Continued nasogastric decompression
Intravenous antibiotics are continued for 7-10 days
Careful monitoring for progression
Enteral feeding may be cautiously reinstituted after clinical improvement and resolution of radiographic signs, often starting with breast milk or hydrolyzed formula
Fluid and electrolyte balance are closely managed
Serial abdominal exams and X-rays may be performed to monitor progress
Specific antibiotics commonly used include ampicillin, gentamicin, and clindamycin or metronidazole, adjusted based on local resistance patterns and culture results
Doses are weight- and age-dependent.
Surgical Management:
Indications for surgery include signs of intestinal perforation (free air in the abdomen on X-ray), abdominal wall necrosis, clinical deterioration despite maximal medical therapy, persistent abdominal distension, fixed dilated bowel loops, or suspicion of portal venous gas
Surgical options include peritoneal drainage (in extremely premature or unstable infants) or laparotomy for bowel resection and ostomy creation
Resection is performed for necrotic or perforated bowel segments
Primary anastamosis is rarely performed in the acute setting
The goal is to remove non-viable bowel and secure abdominal drainage
Surgical approach is guided by the extent of NEC and the infant's stability
Post-operatively, infants require intensive support, including mechanical ventilation, parenteral nutrition, and close monitoring for complications.
Supportive Care:
Continuous cardiorespiratory monitoring
Strict aseptic technique to prevent secondary infections
Nutritional support via total parenteral nutrition (TPN) until enteral feeds are tolerated
Pain management
Management of fluid and electrolyte balance
Blood product transfusions as needed.
Bell Staging Criteria
Stage I Suspected:
Mild illness
Minimal abdominal distension
Mild abdominal tenderness
Rectal bleeding may be absent or minimal
Radiograph may show nonspecific findings like dilated loops or mild bowel wall thickening.
Stage Ii Definite:
Moderate illness
Moderate abdominal distension
Abdominal tenderness
Vomiting may be present
Hematochezia is usually present
Radiograph shows definite pneumatosis intestinalis (gas in the bowel wall)
Bowel sounds may be diminished
Platelet count may drop.
Stage Iii Advanced:
Severe illness
Marked abdominal distension, erythema, and rigidity
Sepsis may be evident
Hypotension, bradycardia, apnea, and respiratory distress
Radiograph shows pneumoperitoneum (free air in the abdominal cavity) or portal venous gas
Signs of peritonitis or perforation.
Complications
Early Complications:
Intestinal perforation leading to peritonitis
Sepsis and septic shock
Disseminated intravascular coagulation (DIC)
Bowel strictures
Necrotic bowel segments
Prolonged ileus.
Late Complications:
Short bowel syndrome requiring long-term TPN and risk of intestinal failure
Growth failure
Neurodevelopmental impairments (cerebral palsy, cognitive deficits)
Recurrent NEC
Intestinal obstruction due to strictures
Malabsorption
Recurrent infections.
Prevention Strategies:
Exclusive breastfeeding whenever possible
Gradual advancement of enteral feeds
Use of probiotics
Judicious use of antibiotics
Early recognition and prompt treatment of sepsis
Avoiding unnecessary umbilical catheterization in the distal bowel
Minimizing hypoxia and hypotension.
Prognosis
Factors Affecting Prognosis:
Gestational age and birth weight (smaller and more premature infants have poorer prognosis)
Severity of NEC (Bell stage)
Presence of intestinal perforation or other major complications
Need for surgery
Development of short bowel syndrome
Presence of sepsis.
Outcomes:
Mortality rates vary significantly with stage, ranging from 0-5% for medically managed NEC to 20-50% for surgically managed NEC, especially those with perforation
Survivors can have significant long-term morbidities impacting growth, development, and quality of life.
Follow Up:
Close monitoring of growth and weight gain
Nutritional assessment and management
Neurodevelopmental screening and early intervention
Monitoring for signs of bowel strictures or obstruction
Surgical follow-up for ostomy care and potential stoma reversal
Long-term assessment for consequences of short bowel syndrome.
Key Points
Exam Focus:
Bell staging criteria are crucial for DNB/NEET SS
Differentiating medical vs
surgical indications for NEC is a high-yield topic
Understand the immediate management steps and antibiotic choices
Recognize signs of perforation and sepsis.
Clinical Pearls:
Always consider NEC in any infant with abdominal distension and feeding intolerance, especially premature infants
Serial abdominal exams are more sensitive than single exams
Bilious aspirates are a red flag
Early surgical consultation is vital for critically ill infants.
Common Mistakes:
Delaying cessation of feeds or NG tube decompression
Underestimating the severity of NEC
Delaying surgical consultation for signs of perforation
Inadequate fluid resuscitation
Broad-spectrum antibiotics that are not appropriate for the suspected pathogens or local resistance.