A 7-day-old girl in the neonatal intensive care unit with truncus arteriosus has poor feeding and abdominal distension. The patient has been hospitalized since birth at 38 weeks gestation via normal spontaneous vaginal delivery and is awaiting adequate weight gain prior to the repair of her congenital heart disease. She has been taking oral formula and has regained her birth weight. Temperature is 35 C (95 F), blood pressure is 60/30 mm Hg, pulse is 180/min, and respirations are 65/min. Pulse oximetry is 82% on room air. Physical examination shows a lethargic, cyanotic neonate with moderate abdominal distension and absent bowel sounds. Bright red blood is visible in her stool. A nasogastric tube is placed for decompression and bilious fluid is recovered. Abdominal x-ray is obtained. What is the most likely diagnosis in this patient?
Necrotizing enterocolitis | |
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This patient's temperature instability, abdominal distension, bloody stools, and x-ray findings are consistent with necrotizing enterocolitis (NEC). Although the majority of affected infants are premature or have a very low birth weight, term infants with reduced mesenteric oxygen delivery from cyanotic congenital heart disease and/or hypotension are also at risk for intestinal ischemia and infarction. Poor intestinal perfusion leads to enterocyte dysfunction, including impaired nutrient absorption, mucosal inflammation and necrosis, and translocation of gas-producing bacteria into the bowel wall.
Classic features of NEC include feeding intolerance, increasing abdominal girth (eg, distension), bloody stools, and vomiting. These symptoms are usually preceded by nonspecific lethargy and vital sign instability (eg, hypothermia), as seen in this patient. The pathognomonic radiologic finding is pneumatosis intestinalis, which represents extravasation of bowel gas into the damaged bowel wall. Air in the portal venous system may also be seen.
Given the risk of lethal septic shock, empiric broad-spectrum antibiotics should be started immediately. Severe bowel wall damage can also result in perforation and pneumoperitoneum and requires surgical intervention.
(Choice A) Clostridioides difficile colitis presents with abdominal distension and watery (sometimes bloody) stools. Neonates are often colonized with C difficile but do not develop symptomatic disease due to absent intestinal receptors to the bacterial toxins.
(Choice B) Intussusception can cause bloody stools but typically presents at age 6 months to 3 years. X-rays can show a soft tissue mass in the right upper quadrant and a crescent sign, which represents the intussusceptum projecting into large bowel gas. A "target sign" or "bull's-eye lesion" (2 concentric circles of telescoped bowel) is classically seen on ultrasound.
(Choice C) Malrotation with midgut volvulus typically presents with bilious vomiting and abdominal pain in neonates or young infants. X-ray usually reveals proximal gaseous distension and distal gasless abdomen due to obstruction involving the duodenum. This infant has pneumatosis, which is highly specific for NEC, as well as visible air in the large bowel.
(Choice D) Milk protein–induced allergic proctocolitis (milk protein intolerance) presents in otherwise healthy infants age 2-8 weeks as blood-tinged stools after sensitization to milk protein. This diagnosis is less likely in this case based on the patient's age, cardiac comorbidity, and severity of illness.
Educational objective:
Necrotizing enterocolitis should be suspected in newborns with temperature instability, feeding intolerance, abdominal distension, and bloody stools. Risk factors include prematurity, hypotension, and congenital heart disease. The hallmark x-ray finding is air within the bowel wall (pneumatosis intestinalis).