Necrotizing Enterocolitis Neonatal

Necrotizing enterocolitis is a life-threatening intestinal illness that primarily strikes premature babies, causing inflammation and death of intestinal tissue that can lead to serious infection and requires urgent medical care.

Table of contents

• What is necrotizing enterocolitis?
• Who is affected by this condition?
• Types of necrotizing enterocolitis
• What causes this condition?
• Risk factors
• Signs and symptoms
• How is it diagnosed?
• Treatment
• Outlook and prognosis

What is necrotizing enterocolitis?

Necrotizing enterocolitis, commonly called NEC, is a serious gastrointestinal problem that affects newborn babies, particularly those born prematurely. The name describes what happens in the body: “necrotizing” means damage and death of cells, “entero” refers to the intestine, and “colitis” means inflammation of the colon, which is the lower part of the intestine^[1].

In babies with NEC, the intestinal tissue becomes inflamed and damaged, causing it to die. This is called necrosis (death of body tissue). The condition can affect both the small and large intestine. When the intestinal wall becomes severely damaged, a hole called a perforation may form in the intestine^[1].

When perforation occurs, bacteria from the intestine can leak into the baby’s abdomen or belly, or even pass into the bloodstream. This can cause a severe, life-threatening infection throughout the body. The intestine can no longer hold waste properly, and sections of the intestine may die and need to be surgically removed^[6].

• Small intestine
• Large intestine (colon)
• Gastrointestinal tract

Who is affected by this condition?

Nearly all babies who develop NEC—9 out of 10—are born prematurely. The condition most commonly affects babies who are born before the 37th week of pregnancy, are fed through a tube in the stomach, and weigh less than 5½ pounds at birth^[1].

Among premature infants, NEC is a common and serious gastrointestinal illness. It affects approximately 1 in 1,000 premature babies. The risk is greatest for babies weighing less than 2 pounds. NEC can affect up to 5 percent of babies in newborn intensive care units, and close to 10% of infants who weigh less than 1,500 grams (about 3 pounds, 4 ounces)^[1][5].

The condition is much less common in full-term babies. Only about 1 in 10,000 full-term babies develop NEC. When full-term infants do get NEC, it is usually associated with an event that causes low oxygen levels, such as a congenital heart defect (a heart problem present at birth)^[1][3].

The smaller and earlier the baby is born, the higher the risk for NEC. The condition is especially common in very sick or premature babies, particularly those who weigh less than 3 pounds, 4 ounces^[3].

Types of necrotizing enterocolitis

Healthcare providers classify NEC into different types based on when symptoms begin and what appears to cause the condition^[1].

Classic NEC is the most common type. It tends to affect infants born before 28 weeks of pregnancy. This type occurs three to six weeks after birth. In most cases, the baby appears stable and is doing well when the condition suddenly develops without warning^[1].

Transfusion-associated NEC occurs when a premature infant receives a blood transfusion to treat anemia (lack of red blood cells). About 1 in 3 premature babies develop NEC within three days of receiving a blood transfusion^[1].

Atypical NEC is rare. In this type, an infant develops NEC in the first week of life or even before the first feeding^[1].

Term infant NEC affects babies born at full term who usually have a birth defect. Possible causes include a congenital heart condition, gastroschisis (intestines that form outside of the body), or low oxygen levels at birth^[1].

Although rare, NEC outbreaks can happen in neonatal intensive care units where several infants develop NEC at the same time. Bacteria such as E. coli or other germs may cause these uncommon outbreaks^[1].

What causes this condition?

Healthcare providers do not know exactly what causes NEC. The specific mechanism and cause are not yet fully understood^[2][3].

What is known is that NEC is caused by bacterial invasion into the intestinal wall. This leads to inflammation and destruction of the wall of the intestine. If not recognized and treated, an intestinal perforation may occur, causing spillage of intestinal contents into the peritoneum (the membrane lining the abdominal cavity), which results in peritonitis (inflammation of the peritoneum)^[2].

Premature infants have weaker immune systems. The immune system is the body’s defense against infections. An infant’s digestive system is also weaker and less mature. When premature babies get an intestinal infection, their immune and digestive systems have difficulty fighting it^[1].

In premature babies, oxygen-carrying blood has a harder time reaching the intestines. Not enough blood and oxygen may reach the baby’s immature intestinal tissues. This diminished blood flow can damage intestinal tissue. The damage allows bacteria to leave the intestines and enter the abdominal cavity or bloodstream^[1][3].

Contact between bacteria from the environment and the immature tissues seems to cause the baby’s body to respond with an inflammatory response (the body’s reaction to harmful stimuli). This can harm the tissues and cause them to die. When this happens, a hole may form in the intestine, causing a severe infection in the baby’s belly^[3].

Risk factors

Several factors may raise a baby’s risk for developing NEC^[3].

Premature birth is the primary risk factor. Premature babies are less mature than full-term babies, meaning they may have trouble with blood and oxygen circulation. Their body is not always ready for digestion and fighting infections. This increases their chance of having NEC. Nearly 70% of NEC cases occur in premature infants born before 36 weeks gestation^[2][3].

Low birth weight is another important risk factor. Prematurity and low birth weight have been identified as primary risks for developing NEC^[2].

Formula feeding increases the risk of NEC. Any premature baby is at risk for NEC, but babies who do not receive human milk, especially their mother’s own milk, are more likely to get NEC. Human milk contains substances that help fight infection and help intestinal cells mature. It is also easier to digest. NEC is much less common in babies who are fed breast milk and is rare in babies who have not received feedings^[3][6].

Specifically, high osmotic strength formula feeding has been implicated as a risk factor^[2].

Difficult birth or low oxygen levels at birth increase the likelihood of NEC. Babies who had a difficult birth or low oxygen levels at birth are more likely to get NEC. When there is too little oxygen, the body sends blood and oxygen to the brain and heart first. This reduces the blood flow to the intestinal tract, which can cause less oxygen in blood to reach the colon^[3].

Infections in the intestine raise the risk. Babies with infections in their intestines are more likely to get NEC^[3].

Genetic factors may also play a role in the development of necrotizing enterocolitis^[2].

Signs and symptoms

NEC typically occurs two to six weeks after birth, depending on the type and cause. In premature infants, onset is typically during the first several weeks after birth, with the age of onset inversely related to gestational age at birth. In term infants, the reported median age of onset is 1 to 3 days, but onset may occur as late as age 1 month^[5].

Symptoms may develop over a few days or appear suddenly in babies. The signs and symptoms of NEC are nonspecific, so healthcare providers must remain suspicious when presented with these signs and symptoms in newborns^[2].

Initial symptoms may be subtle and can include one or more of the following^[5][6]:

• Belly bloating or swelling (abdominal distention)
• A swollen or tender belly
• Red, blue, or gray discoloration of the belly
• Abdominal tenderness
• Trouble feeding or poor feeding
• Food does not move through to the intestines
• Food staying in the stomach longer than expected
• Delayed gastric emptying
• Vomiting, including green vomit containing bile
• Constipation
• Diarrhea and dark or bloody stools (bowel movements)
• Bloody bowel movements (hematochezia)
• Greenish-colored fluid (bile) in the stomach
• Decreased bowel sounds or ileus (blockage of the intestine)
• Abdominal wall erythema (redness) in advanced stages

Systemic signs (affecting the whole body) are nonspecific and can include any combination of the following^[5][6]:

• Being lethargic or less active (sluggishness)
• A low or unstable body temperature
• Breathing that stops and starts (apnea)
• Slow heart rate (bradycardia)
• Low blood pressure (hypotension)
• Decreased peripheral perfusion (poor blood flow to outer parts of the body)
• Shock in advanced stages
• Cardiovascular collapse
• Bleeding diathesis (consumption coagulopathy, a problem with blood clotting)

Symptoms of NEC can vary from baby to baby and can be similar to those caused by other digestive problems^[6].

How is it diagnosed?

Healthcare providers should obtain radiographic studies if any concern about NEC is present. Laboratory studies should be pursued, especially if the abdominal study findings are worrisome or the baby is manifesting any systemic signs^[5].

In babies with symptoms of NEC, a diagnosis can be confirmed if an abnormal gas pattern shows up on an X-ray. This looks like a bubbly or streaky appearance of gas in the walls of the intestine. In severe cases, air escapes from the intestine and shows up in the large veins of the liver or the abdominal cavity^[6].

A complete blood count (CBC) with manual differential is usually performed and may be repeated at least every 6 hours if the patient’s clinical status continues to deteriorate. Relevant findings may include^[5]:

• White blood cell count: Moderate to profound neutropenia (low absolute neutrophil count, less than 1,500 per microliter) strongly suggests established sepsis (widespread infection)
• Hematocrit and hemoglobin: Blood loss from bloody stools or a developing consumptive coagulopathy can appear as an acute decrease in hematocrit; an elevated hemoglobin level and hematocrit may indicate hemoconcentration due to notable accumulation of fluid outside blood vessels
• Platelet count: Thrombocytopenia (low platelet count) may be present

Other laboratory findings include^[5]:

• Blood culture is usually negative
• Hyponatremia: An acute decrease in serum sodium (less than 130 milliequivalents per liter) is alarming
• Low serum bicarbonate (less than 20) may be seen in babies with poor tissue perfusion, sepsis, and bowel necrosis

A doctor may order other tests such as abdominal ultrasound or paracentesis (removing fluid from the abdomen for testing) to help with diagnosis^[5].

Treatment

Treatment of infants with NEC generally includes a regimen of bowel rest, gastric decompression, systemic antibiotics, and parenteral nutrition (nutrition given through a vein rather than by mouth)^[14].

Patients with mild NEC require gastrointestinal rest to allow the intestinal inflammatory process to resolve. These babies are traditionally kept on a diet of nothing by mouth for 7 to 10 days. Switching to intravenous (IV) feedings helps by giving the intestines time to heal^[1][11].

Cessation of feeding and initiation of broad-spectrum antibiotics are standard treatments. Antibiotics empirically cover anaerobic bacteria and Gram-negative bacteria. The most common regimen reported is intravenous administration of ampicillin and gentamicin combined with metronidazole for a period of 10 to 14 days^[13].

However, no sufficient evidence has been found for any specific recommendation on the choice of antibiotics, the route of administration, or the duration in infants treated for NEC. Several studies have investigated different antibiotic combinations, but none demonstrated clear superiority^[13].

Some infants need surgery to remove the damaged intestine. Infants with perforation are generally operated upon. During surgery, the damaged or dead portion of the intestine is removed. There has been recent interest in primary peritoneal drainage as an alternative surgical approach^[1][14].

Many babies require difficult intravenous access for prolonged parenteral nutrition, which frequently requires placing central venous catheters. These have attendant risks and complications that include thromboembolic events (blood clots) and nosocomial infections (infections acquired in the hospital)^[11].

Outlook and prognosis

NEC is a life-threatening illness with a mortality rate as high as 50 percent. As NEC progresses, it can lead to intestinal perforation causing peritonitis, sepsis, and death^[2].

In some infants, NEC is mild. Others experience severe, life-threatening symptoms^[1].

The National Center for Health Statistics and multicenter trials have estimated that there are between 1,200 and 9,600 cases per year in the United States, resulting in up to 2,688 deaths^[14].

Prevention of NEC remains challenging. Avoidance of preterm birth, use of antenatal steroids, and breast-milk feeding are practices that offer the greatest potential benefits^[14].