IS case 464: Pneumatosis intestinalis secondary to necrotizing enterocolitis
Imaging Sciences URMC 2010
Publication Date: 2010-08-30
Patient is a two-day-old, ex-30 week premature, infant found to have increasing abdominal distension and residuals after initiation of tube feedings. After developing signs of sepsis the patient required pressors and intubation. A chest radiograph was obtained and subsequently the patient was taken to the OR on the basis of the clinical and radiologic findings.
Abdominal radiograph showed dilated loops of large and small bowel which have a diffusely mottled, bubble-like appearance. There was a rim of lucency tracking along the walls of the bowel. There was no free air or portal venous gas.
Necrotizing enterocolitis (NEC) is an inflammatory disease of the lower gastrointestinal tract of 1-5% of neonates in the intensive care setting. Prematurity is a major risk factor, as well as low birth weight. However term infants with congenital cardiac malformations account for 10% of cases. These infants present between week 1 and 3 of life and have signs ranging from feeding intolerance and diarrhea to abdominal erythema and septic shock. Mortality for NEC is estimated at between 30-35% but as high as 65% if complicated by perforation. Bowel rest, hydration and antibiotics are the first line of management, but surgery is indicated for complications such as peritonitis, bowel necrosis or perforation.
The only true radiologic criterion for surgical intervention is free air. However, radiologic evaluation is directed at detecting bowel compromise early in the natural history of the disease and may guide the surgeon to intervene to minimize complications. Radiographic stages mirror the progression of the disease, and include (in increasing severity): distended bowel, distended bowel with mottling in a pattern suggestive of stool, focal dilation of bowel loops, separation or focal thickening of bowel loops, featureless or separated bowel loops, possible pneumatosis with other findings, fixed distension of loops on serial films, pneumatosis (definite findings), portal venous gas, and pneumoperitoneum.
Pneumatosis intestinalis is thought to result from mucosal perforation due to local ischemia resulting from infection, immature immunity, intraluminal contents, vasoconstriction, or local inflammation. Air either from bowel lumen or gas-producing bacteria infiltrating the area dissects through the bowel wall. Bacteria can then access the systemic circulation and cause sepsis, or else the local inflammatory response compromises the microvasculature and produces tissue ischemia and subsequent perforation. However, pneumatosis alone is not an indication for surgery as the bowel may recover with conservative therapy, and can be found in several conditions such as obstruction, Hirschsprung's, and obstruction.
In this case the finding of pneumatosis intestinalis, combined with the clinical scenario of respiratory failure and circulatory collapse, guided the surgeon to intervene. Pathology findings were consistent with NEC.
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