Ileocecal region is a watershed area and often affected. Mucosa demonstrates hemorrhage and acute inflammation. However, the mucosa is intact with no actual mucosal sloughing -- thus, this bowel is most consistent with the resolving phase of necrotizing enterocolitis.
Dissecting hemorrhage in the underlying stroma and mucosal inflammation are evident. Can you spot the neutrophils in the epithelium? (Look left at about 10 o'clock). Again, the mucosal architecture is fairly intact. This represents an area less severely affected, as complete mucosal necrosis is not evident.
Necrotizing enterocolitis is most commonly seen in premature infants, affecting approximately 1 out of 10 infants born less than 1500 grams (3 lbs and 4 oz) and carries a mortality rate of up to 50%. The etiology is still not completely clear, but intestinal ischemia from hypoperfusion (maternal hypertension or pre-eclampsia leading to placental insufficiency), immaturity of GI tract, genetic susceptibility and alteration of gut bacteria have all been implicated. It is probably a complex interplay of all these factors, ultimately leading to mucosal breakdown and necrosis of the bowel. Sepsis and shock will set in in advanced disease.1,2
Grossly, the involved segment of bowel may be distended, congested or entirely gangrenous. Gas bubbles may be visible in the bowel wall. The terminal ileum and right colon are preferentially affected. Microscopically, mucosal or transmural ulceration, hemorrhage, necrosis and submucosal gas collections may be found.
Early signs are often subtle and nonspecific such as lethargy, feeding intolerance and abdominal tenderness. More specific signs include abdominal distention, blood stools, absent bowel sounds and vomiting. Radiographs may demonstrate penumatosis intestinalis (gas within the abdominal wall).
In milder cases, conservative and medical management (stop enteral feedings, antibiotics, IVF and parental nutrition) may suffice. Surgical resection may be required in more severe instances.
Depending on the severity of the disease, necrotizing enterocolitis carries a mortality rate ranging from 10-50% in premature infants. Nearly 1/3 have a fulminant course with intestinal perforation, requiring bowel resection. Long-term complications are common and include short gut syndrome, malabsorption, stricture and fibrosis from the healing process (post-NEC strictures).1,2
1 Kumar V, Abbas AK, Fausto N. Robbins and Cotran Pathologic Basis of Disease. 7th Ed. Philadelphia, PA: Elsevier; 2005: 483.
2 Springer, Shelley. Necrotizing Enterocolitis: eMedicine. Last updated on 9/22/09. Available at: http://emedicine.medscape.com/article/977956-overview