Neonatal Necrotizing Enterocolitis (NEC)

Nelson Textbook of Pediatrics, 18th editon

By:

S.M.A Shahkarami, MDResident of Pediatrics

Isfahan University of Medical Sciences

GENERAL CONSIDERATIONS

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NEC is the most common life-threatening emergency of the

gastrointestinal tract in the newborn period.

Mucosal or transmural necrosis of the intestine.

The cause of NEC remains unclear (multifactorial).

The incidence of NEC is 1–5% of infants in NICU

Both incidence and case fatality rates increase with decreasing birthweight and gestational age.

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PATHOLOGY AND PATHOGENESIS

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Development of a necrotic segment of intestine,

Gas accumulation in the submucosa of the bowel wall (pneumatosis intestinalis)

Progression of the necrosis to perforation, peritonitis, sepsis, and death

The distal part of the ileum and the proximal segment of colon are involved most frequently

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This triad has classically been linked to NEC:

intestinal ischemia (injury),

enteral nutrition (metabolic substrate),

and pathogenic organisms

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The greatest risk factor for NEC is prematurity.

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S.M.A Shahkarami, MD 9

Coagulation necrosis is the characteristic histologic finding of intestinal specimens.

Various bacterial and viral agents, including Escherichia coli, Klebsiella, Clostridium perfringens, Staphylococcus epidermidis, and rotavirus, have been recovered from cultures.

Nonetheless, in most situations, no pathogen is identified

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NEC rarely occurs before the initiation of enteral feeding and is much less common in infants fed human milk.

Aggressive enteral feeding may predispose to the development of NEC.

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CLINICAL MANIFESTATIONS

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The onset of NEC usually occurs in the 1st 2 wk of life but can be as late as 3 mo of age in VLBW infants.

Age of onset is inversely related to gestational age.

The 1st signs of impending disease may be nonspecific including lethargy and temperature instability or related to gastrointestinal pathology such as abdominal distention and gastric retention.

Obvious bloody stools are seen in 25% of patients.

Because of nonspecific signs, sepsis may be suspected before NEC.

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The spectrum of illness is broad and ranges from mild

disease with only guaiac-positive stools to severe illness with bowel perforation, peritonitis, systemic inflammatory response syndrome, shock, and death.

Progression may be rapidbut

it is unusual for the disease to progress from mild to severe

after 72 hr

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DIAGNOSIS

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Plain abdominal x-rays are essential to make a diagnosis of NEC

pneumatosis intestinalis (air in the bowel wall) confirms the clinical suspicion of NEC and is diagnostic

Portal venous gas is a sign of severe disease, and pneumoperitoneum indicates a perforation.

Hepatic ultrasonography may detect portal venous gas despite normal abdominal roentgenograms.

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Differential Diagnosis

specific infections (systemic or intestinal) gastrointestinal obstruction Volvulus isolated intestinal perforation

Idiopathic focal intestinal perforation can occur spontaneously

Or

after the early use of postnatal steroids and indomethacin.

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TREATMENT

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Rapid initiation of therapy is required for suspected as well as proven NEC

No definitive treatment ,therefore, therapy is directed at supportive care: cessation of feeding, nasogastric decompression, and administration of

intravenous fluids. Careful attention to respiratory status, Ventilation should be assisted in the presence of apnea or if abdominal

distention is contributing to hypoxia and hypercapnia. coagulation profile, acid-base and electrolyte balance systemic antibiotics (with broad coverage based on the antibiotic sensitivity

patterns of the gram-positive, gram-negative, and anaerobic organisms) should be started immediately.

If present, umbilical catheters should be removed

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Close Monitoring

frequent physical assessments

sequential anteroposterior and cross-table lateral or lateral decubitus abdominal x-rays to detect intestinal perforation

and serial determination of hematologic, electrolyte, and acid-base status

Gown and glove isolation

and grouping infants from other infants to contain an epidemic.

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A surgeon should be consulted early

Indications for surgery: evidence of perforation on abdominal X-rays:(pneumoperitoneum) positive abdominal paracentesis (stool or organism on Gram stain

from peritoneal fluid).

Relative indications for exploratory laparotomy: a single fixed bowel loop on roentgenograms, abdominal wall

erythema, or a palpable mass

Ideally, surgery should be performed after intestinal necrosis develops, but before perforation and peritonitis occurs.

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The role of peritoneal drainage in lieu of laparotomy in a patient with perforation secondary to NEC remains to be determined

more successful in patients with isolated intestinal perforation

In many patients with isolated intestinal perforation treated by drainage, no further surgical procedure is needed

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PROGNOSIS

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Medical management fails in about 20–40% of patients with pneumatosis intestinalis at diagnosis; of these, 10–30% die.

Early postoperative complications include wound infection, dehiscence, and stomal problems (prolapse, necrosis).

Later complications: intestinal strictures that develop at the site of the necrotizing lesion in about 10% of

surgically or medically managed patients.

After massive intestinal resection, complications from postoperative NEC include short-bowel syndrome (malabsorption, growth failure, malnutrition),

complications related to central venous catheters (sepsis, thrombosis), and cholestatic jaundice.

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PREVENTION

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Newborns exclusively breast-fed have a reduced risk of NEC

Whereas early initiation of aggressive feeding protocols may increase the risk of NEC in VLBW infants

gut stimulation protocol of minimal enteral feeds followed by

judicious volume advancement may decrease↓ the risk

Probiotic preparations have also decreased the incidence of NEC.

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HIGHLY TRULY YOURS&

WARM REGARDS

S.M.A Shahkarami, MD

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