Necrotizing enterocolitis: Clinical sciences

Necrotizing enterocolitis, or NEC for short, is a life-threatening condition most often seen in premature infants that can lead to intestinal necrosis and perforation. NEC commonly presents with feeding intolerance, bloody stools, and abdominal distension soon after enteral feeds are initiated.

Infants who survive NEC face many long-term sequelae, including short-gut syndrome, intestinal strictures, and neurodevelopmental delays. On the basis of history and physical exam findings, you can make a clinical diagnosis of NEC, and imaging can be used to support the diagnosis.

Now, here’s a clinical pearl! Breast milk contains macronutrients, micronutrients, natural prebiotics, and antibodies that offer protection against NEC in premature and low birth weight infants! For this reason, donor breast milk is often given to premature neonates whose caregiver is absent or cannot produce sufficient breast milk.

When a pediatric patient presents with a chief concern suggesting NEC, you should first perform an ABCDE assessment to determine if they are unstable or stable. If unstable, stabilize the airway, breathing, and circulation; and you may even need to intubate the patient. Next, obtain IV access and start broad-spectrum IV antibiotics. Put your patient on continuous vital sign monitoring, including blood pressure, heart rate, and pulse oximetry, and begin supplemental oxygen, if needed.

Once you stabilize the patient, obtain a focused history and physical exam, and order abdominal X-rays in the anteroposterior and lateral views. When obtaining the history, be sure to note any risk factors for NEC, which include prematurity or low birth weight. The infant may have developed a sudden change in feeding tolerance, or you may note vomiting, diarrhea, or bloody stools. Additionally, some infants with NEC might have apneic episodes lasting 20 seconds or more.

On the physical exam, the infant may show signs of hemodynamic instability, like hypotension; and signs of respiratory distress, such as tachypnea, retractions, or grunting. Meanwhile, the abdominal exam typically reveals distension, tenderness, and decreased or absent bowel sounds. You may even detect a palpable abdominal mass due to intestinal edema. Finally, in some infants, you might notice abdominal wall erythema from intestinal necrosis or crepitus from free air in the abdominal cavity after intestinal perforation.

As far as X-ray results go, you will typically see dilated loops of bowel and pneumatosis intestinalis, which is visible gas within the necrotic intestinal wall, and is a pathognomonic finding for NEC. Later findings can include portal venous gas, which is gas that has escaped into the hepatic portal vein and its branches, and pneumoperitoneum, which is free air within the abdominal cavity. A large amount of free air can be identified by the “football” sign on AP films.

With this combination of clinical and X-ray findings, you can diagnose NEC with intestinal perforation. Because this is a life-threatening condition, consult the surgery team immediately for exploratory laparotomy and resection of necrotic bowel. As far as medical management goes, be sure to stop all enteral feeds, continue broad-spectrum IV antibiotics, start IV fluids, and, if needed, transfuse blood products. After surgery, the neonate will require bowel rest and parenteral nutrition.

Now, here’s a clinical pearl to keep in mind! Radiographic evidence of pneumoperitoneum in a premature or low birth weight neonate almost always indicates NEC with intestinal perforation. However, pneumoperitoneum can also be seen in spontaneous intestinal perforation, or SIP, which is a single perforation site in an otherwise healthy bowel. SIP is associated with early use of postnatal corticosteroids and indomethacin. Clinically, neonates with SIP usually aren’t as ill as neonates with NEC, and a definitive diagnosis can be made by surgical exploration. Moreover, the presence of a healthy bowel indicates SIP while a necrotic bowel indicates NEC.

Now, let’s go back to the ABCDE assessment and look at stable infants with NEC. In this case, obtain a focused history and physical exam, and order a CBC, CMP, and blood culture. When obtaining the history, again, be sure to assess the infant’s risk factors for NEC, which include prematurity and low birth weight. Additionally, the infant might have developed sudden feeding intolerance, vomiting, diarrhea, or bloody stools.

Meanwhile, the physical exam findings may include abdominal distension or tenderness, as well as decreased bowel sounds.

Next, the CBC may show thrombocytopenia or neutropenia; the CMP may reveal electrolyte derangements like hyponatremia or metabolic acidosis; and the blood culture might be positive for infectious organisms.

With these clinical findings, you should suspect NEC, and promptly order abdominal X-rays in the anteroposterior and lateral views. Typically, X-rays reveal dilated loops of bowel, and sometimes, you might visualize pneumatosis intestinalis. With these findings, you can diagnose NEC!