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What is Necrotising Enterocolitis?


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What is Necrotising Enterocolitis?

September 1, 2023

Necrotising Enterocolitis (NEC) is a catastrophic gastrointestinal illness that is seen predominantly in babies born prematurely, especially those born at less than 30 weeks gestation. It is sometimes also seen in babies with intrauterine growth restrictions, babies who are born very ill, or babies with anatomical differences that may reduce blood flow to the gut (for example, heart defects). NEC occurs when bacteria infect and irritate the immature neonatal bowel. This infection can cause tissue necrosis (tissue death) within the bowel and eventually lead to something called a perforation. This is when the irritated and necrosed bowel has torn and there is a hole in the gut lining, meaning that the contents usually contained within the bowel wall (like bacteria, stool and air) can now leak out into the abdominal cavity. Once the bowel has perforated, it is considered a medical emergency and surgery must be performed immediately.

NEC can be difficult to definitively diagnose prior to the complication of perforation. Perforations are relatively easy to diagnose because x-ray films show that there is air inside the abdominal cavity indicating that the bowel has been leaking. The medical team will usually use a combination of clinical data, ultrasound scans and x-ray films to looks for signs of NEC. Surgical intervention is recommended when it is presumed that the bowel has necrosed in order to remove the deceased bowel and prevent spread. A bowel perforation is a clear sign of necrosis, but ideally surgical intervention occurs before then. The goal is to avoid operating on babies who do not yet have necrosis, but not wait on a baby that does, a delicate balancing act.

A baby with suspected NEC may exhibit the following clinical symptoms. Abdominal distention, bilious (green/yellow) vomiting, feed intolerance, loose stools, bloody stools and a change in their baseline vital signs. This includes changes in their heart rate, temperature, level of respiratory support, oxygen requirement, and changes in their bloodwork. Their blood work often shows signs of infection and sometimes even bacteria growing in their blood stream.

On x-ray films, the medical team and radiologists may see a thickened bowel wall, dilated or enlarged loops of bowel, pneumatosis (air in the bowel wall), portal venous gas (a clear indication that there is trouble in the gut) and ultimately a perforation. Similarly, an ultrasound scan can also show these signs as well as reduced blood flow to the bowel.

Treatment for NEC is relatively standard. The medical team will try to manage suspected NEC medically before resorting to surgical intervention if caught early enough. The baby will be placed on gut rest, meaning they will not have any oral feeds to give their bowels a rest. At this time all their nutritional needs will be met using intravenous nutrition which is a mix of sugar, fats and vitamins going directly into a baby’s blood stream via an intravenous line. A nasogastric tube will be inserted and left on free drainage to relieve the stomach and intestines of any residual gastric contents or air, for further reading on this topic, please read our blog on What is a nasogastric and orogastric tube? The baby will also be placed on three different antibiotics (amoxicillin, amikacin and metronidazole) to help fight the bad bacteria in the gut. The baby will usually require an endotracheal breathing tube for ventilation support and sedation (such as morphine and midazolam) to manage their pain and discomfort during this time. A urinary catheter will help drain their bladder and the medical team will monitor how much fluid goes into the baby and how much comes out. This is called a fluid balance. Sometimes when babies are medically unstable, their kidney’s do not work as well, and they have trouble making urine. When a baby in unable to make urine, they can become very oedematous (swollen), in which case they may need some medication to help them. The baby may also require additional medication to help with their blood pressure and heart rate.

When it becomes evident that there is necrosis in the bowel, or there has been a perforation, the baby will require surgical intervention. In addition to all the treatments listed above, the baby will be transported to theatre to undergo a laparotomy. During this procedure, the surgeon will open the baby’s abdomen and confirm the diagnosis of NEC by assessing the bowel. They will remove the necrotic bowel and thoroughly check the remaining bowel for any additional signs of necrosis. Sometimes they only need to remove a small portion of bowel, and other times a large amount of bowel needs to be removed from multiple different segments.

The surgeon will only remove severely damaged bowel. The surgeon will surgically join the healthy ends of the intestine back together but generally they will need to make a stoma because the baby is very un-well so it is safest to bring out a stoma to let the gut rest and wait for the swelling to subside. A stoma sits on the abdomen and collects the fluid contents (chyme), that transit through the intestine, into a stoma bag. The healthy proximal end of the intestine that descends from the stomach and the healthy distal end of the intestine that continues down to the rectum are brought up to the surface of the abdomen and an ostomy appliance is placed on the tummy to collect the chyme. To read further on this topic please read What is a stoma?

Once safe to do so, it is standard of care to perform chyme reinfusion while the baby has a stoma. Chyme reinfusion is a therapy whereby the chyme that comes out into the ostomy appliance, is reinfused downstream through the distal end of the stoma. To read further on this topic please read What is chyme reinfusion? This is completed until the baby does not require a stoma anymore and the surgeon reverses their stoma.

The road to recovery for babies with NEC is often difficult. They are often very sick, requiring significant medical support while they recover and heal. After they overcome the initial period of being very unwell, they often have difficulty with their growth due to the reduced surface area in their bowel for nutrient absorption. When a baby has had a significant bowel reception of necrosed bowel they often continue to struggle with growth and vitamin deficiency throughout their childhood. To read further on this topic, please read Nutrition in Intestinal Failure and Nutrient Absorption in the Gastrointestinal System.

The babies who have had stoma formations will eventually need to undergo another operation to reverse their stoma and join the two healthy ends of their bowel back together. This operation is usually performed once the infant has healed fully and gained weight. Many babies who have had NEC are pre-term babies who were very small at the time of their initial surgery, so the surgeons prefer to wait to perform the second surgery when they are much older and closer to the size of a term baby. Once the stoma has been reversed, the baby’s gastrointestinal tract will function normally like it did before they became un-well. Babies often recover much faster from this surgery, especially if they have had chyme reinfusion therapy. Once they have fully recovered from stoma reversal surgery, they begin getting ready for discharge home.

The journey home for these infants is complex. After they have healed from their surgery, they need to learn to feed on their own and breath without extra support. Many babies who have had NEC have long extended hospital stays and do not leave the hospital before they turn 100 days old, a NICU milestone. No one is more excited than their parents when babies are finally discharged home. The stress and anxiety that comes with having a baby with NEC is overwhelming and they do an amazing job, supporting each other, and their baby along the way.

Written by

Taylor Harrington, NICU Nurse.

Newborn Services Clinical Practice Committee.Necrotising Enterocolitis (NEC) in the neonate. 2020. Starship Child HealthClinical Guideline.

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