History: 28 w/o infant present abdominal distention.

Factoid Discussion: Necrotizing enterocolitis is a serious disease of newborns. It is characterized by various degrees of mucosal or transmural necrosis of the intestine. Very small, ill preterm infants are particularly susceptible to NEC, a rising incidence may reflect improved survival of this high-risk group of patients. The disease rarely occurs in term infants.

Etiology and Pathogenesis: The cause of necrotizing enterocolitis is unkown. Many factors may contribute to the development of a nectrotic segment of intenstine, the gas accumulation in the submucosa of the bowel wall (pneumatosis intestinalis), and progression of the necrosis leading to perforation, sepsis and death. The distal ileum and proximal colon are involved most frequently; fatal cases have gangrene from stomache to the rectum. Various factors such as polycythemia, hypertonic milk or oral medicines or too rapid feeding protocols may contribute to mucosal injury and subsequent infection leading to bowel necrosis. NEC also occurs in premature infants without stress, particularly during epidemics. The clustering of cases suggests a primary role for an infectious agent; Clostridium perfringens, Escherichia Coli, Staphylococcus epidermidis and rotavirus have been recovered from cultures. Nonetheless, in most situations no pathogen is identified.

Radiologic findings: Plain abdominal X-rays may demonstrate pneumatosis intestinales, a finding that is diagnostic of NEC in a newborn infant; 50-75% of patients have pneumotosis when treament is started. Portal vein gas is a sign of severe disease, and pneumoperitoneum indicates a perforation.

Epidemiology: Incidence ranges from 1-5% of admissions to neonatal intensive care units Onset usually occurs in the first 2 wks. But can occur as late as 3 months of age in very low birth weight infants. Age of onset is inversely related to gestational age.

Clinical Manifestations: The first signs are abdominal distention with gastric retention. Manifestations usually develop after onset of enteric feedings. Obvious bloody stools are seen in 25% of patients. The onset is often insidious, and sepsis may be suspected before an intestinal lesion is noted. There is a wide spectrum of illness from mild with only guaiac-positive stools to severe peritonitis, bowel perforation, systemic inflammatory response syndrome, shock and death. Progression may be rapid, but it is unusual for the disease to progress from mild to severe after 72 hrs.

Differential Diagnosis:

1.   Infectious disease
2.   Obstruction
3.   Volvulus
4.   Drugs
5.   Hirschprung's Disease
6.   Annular pancreas
7.   Intussusception
8.   Meconium Plug

Diagnosis:
A very high index of suspicion in treating infants at risk is essential. Cultures and X-rays may be diagnostic. Ultrasonography may detect portal venous gas despite normal abdominal X-rays.

Treatment:
Intensive therapy is advisable for suspected as well as diagnosed cases. Cessation of feeding, nasogastric decompression, and intravenous fluids with careful attention to respiratory status, coagulation profile, and acid-base and electrolyte balance are very important. Once blood cultures are taken, systemic antibiotics with an aminoglycoside should be started. When present, umbilical catheters should be removed and ventilation should be assisted if distention is contributing to hypoxia and hypercapnia. If hypotension develops, resuscitation with crystalloid, blood, plasma and dopamine is essential.
The patient\\\'s course should be monitored by frequent cross-table lateral abdominal X-rays in search of perforation and by hematocrit, platelet, electrolyte and acid-base determinations. Gown and glove isolation and grouping infants at similar increased risk into cohorts separate from other infants should be instituted to contain an epidemic.
A surgeon should be consulted early in the course of treatment. Evidence of perforation is usually an indication for resection of necrotic bowel. Pneumoperitoneum and brown paracentesis fluid suggest perforation. Failure to respond to medical management, a single fixed bowel loop, erythema of the abdominal wall, and a palpable mass are additional indications for exploratory laparatomy, resection of necrotic bowel, and external ostomy diversion. Peritoneal drainage may be helpful for patients in extremis with peritonitis who are unable to withstand bowel resection.