Necrotizing Enterocolitis (NEC)

By Dr. Namrata Todurkar

Photo Credit: https://www.sickkids.ca/

There is hardly a NICU health care staff who has not been shaken to the core by Necrotizing Enterocolitis (NEC). NEC is nothing but the ‘death of tissues in the intestine’. The progression is very rapid, and the outcomes are almost always devastating. Even after years of research, there is no clear answer as to why NEC happens in the first place. There has been no decline in the incidence of NEC over the past decades and it remains one of the most important challenges to Neonatologists to date. The bitter truth however is that NEC is untreatable. Every parent of a preterm infant should be aware of NEC to take informed decisions in the NICU. This blog post will give an overview of the condition itself, management approaches, complications of NEC (both short-term and long-term), and preventive measures.

NEC develops after the initiation of feeds. It is the most common gastrointestinal emergency in the NICU and a leading cause of death among preterm and very low birth weight infants (birth weight less than 1500 grams). NEC may also develop in term infants who have certain conditions that lead to decreased blood flow to the gut such as congenital heart disease (CHD), birth asphyxia, intrauterine growth restriction, severe infection, or respiratory disease.

The current understanding of the disease is that it is multifactorial. The most convincing risk factors for NEC are prematurity and low birth weight. Formula feeding is associated with a 2.8 fold increased risk of NEC development, compared to feeding with human milk. A decrease in oxygen delivery to the gut will damage the lining of the intestinal wall. This will allow the bacteria that normally reside inside the intestine to invade the wall and cause local infection and inflammation. All these events eventually lead to rupture or perforation of the intestine.

An affected infant with NEC can have a wide range of symptoms ranging from vomiting, tummy distension, and bloody stools to low blood pressure, lethargy, and respiratory failure. Also, the time course for worsening can be variable, with the potential for rapid progression if unrecognized. Abdominal X-rays and ultrasound along with blood investigations help establish the diagnosis. The diagnosis of NEC is usually confirmed by the presence of gas or air bubbles in the wall of the intestine on an abdominal X-ray.

Necrotizing Enterocolitis that recovers only by conservative management is called ‘Medical NEC’. And the more complex ones are called ‘Surgical NEC’. The most important thing that differentiates medical NEC from surgical NEC is the integrity of the intestine. If free air or fluid with the debris is noted in the abdominal cavity, it indicates that the intestinal wall has given away.

Treatment for NEC is generally supportive care since no therapy or intervention has been identified to slow or stop the progression of this disease process. Prompt initiation of broad-spectrum antibiotics, stopping feeds, and gastric decompression are the keys to treatment. Despite optimal neonatal intensive care, up to 50% of infants with NEC will require surgical intervention.

Mortality from NEC reaches 50% in patients that require surgery. Surgery consists of removing the portion of the intestine that has ruptured or is about to rupture. The surgeons preserve as much intestine as possible and may resort to creating an ostomy gut connected to abdominal skin) in certain circumstances. The baby will poop out of the stoma (opening of the ostomy), which will remain in place until the baby recovers. Surgeons may then perform a reversal of stoma to restore continuity of the bowel so that the poop will come out of the anus once again.

The short-term consequences of NEC range from shock, bleeding into the brain, growth failure, and electrolyte disturbances to sepsis, respiratory failure, and death. NEC survivors may suffer from long-term complications such as intestinal stricture (obstruction of the gut), short bowel syndrome (SBS), and neurodevelopmental impairment (NDI). The most common delayed complication in survivors of both medical and surgical NEC is the formation of intestinal strictures, leading to feeding intolerance. It can occur in up to 35% of NEC survivors. Other complications associated with NEC include infections from long-term central venous access and parenteral nutrition-associated liver disease.

Long-term NDI is common in survivors of surgical NEC. Previous studies have demonstrated NDI in up to 50% of NEC survivors at 12 to 20 months of age. The risk of cerebral palsy and cognitive and severe visual impairment was significantly higher in neonates with NEC, more so in infants who had a perforation of the bowel. The finding that an increased risk of NDI is even more relevant to neonates with surgically managed NEC probably reflects the severity of illness with resultant exposure to a higher level of harmful chemical mediators for a longer duration. Survivors of surgical NEC are also expected to be subjected to longer and possibly more significant exposure to suboptimal nutrition and multiple episodes of sepsis due to prolonged enteral feed intolerance and dependence on central venous catheters for parenteral nutrition. NEC has a significant adverse impact on the preterm brain, and this has been represented in the diagram below.

Prevention: Current evidence suggests that the two most promising strategies for NEC prevention are the exclusive use of human milk and probiotic supplementation. In addition to the practice of using human milk, many centers have demonstrated that carefully regimented feeding regimens may decrease the incidence of NEC. Donor milk supplementation should be considered in place of preterm formula. Despite the theoretical benefits, several research studies have found no difference in NEC incidence with fast versus slow feeding advancement, delayed versus early initiation of enteral feeds, and continuous versus bolus enteral feeding. There are several randomized controlled trials showing a decrease in NEC incidence in very low birth weight infants after supplementation with probiotics. And lastly, antenatal steroids are given to pregnant women who are at risk of preterm birth, which also help prevent necrotizing enterocolitis.

Overall, it is important to remember that NEC is more than just an impact on the bowel. It is a systemic disease with significant adverse outcomes and parents may have to carefully consider treatment options for their little one by keeping the long-term quality of life in mind.

More information about NEC can be obtained on the following website: necsociety.org

Dr. Namrata Todurkar, MBBS, MD (Pediatrics), DNB (Pediatrics). Fellowship in Neonatology from National Neonatology Forum India. Fellow in Neonatal-Perinatal Medicine at the University of British Columbia. Areas of interest: Neonatal nutrition, Fluid and Electrolyte Management, Inborn Errors, Neurodevelopmental follow-up of preterm infants. Dr. Todurkar is a volunteer blogger at CPBF.

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