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Necrotizing Enterocolitis

Definition

Necrotizing enterocolitis is a serious bacterial infection in the intestine, primarily of sick or premature newborn infants. It can cause the death (necrosis) of intestinal tissue and progress to blood poisoning (septicemia).

Description

Necrotizing enterocolitis develops in approximately 10% of newborns weighing less than 800 g (under 2 lbs). It is a serious infection that can produce complications in the intestine itself—such as ulcers, perforations (holes) in the intestinal wall, and tissue necrosis—as well as progress to life-threatening septicemia. Necrotizing enterocolitis most commonly affects the lower portion of the small intestine (ileum). It is less common in the colon and upper small bowel.

Causes and symptoms

The cause of necrotizing enterocolitis is not clear. It is believed that the infection usually develops after the bowel wall has already been weakened or damaged by a lack of oxygen, predisposing it to bacterial invasion. Bacteria proliferate in the bowel and cause a deep infection that can kill bowel tissue and spread to the bloodstream.

Necrotizing enterocolitis almost always occurs in the first month of life. Infants who require tube feedings may have an increased risk for the disorder. A number of other conditions also make newborns susceptible, including respiratory distress syndrome, congenital heart problems, and episodes of apnea (cessation of breathing). The primary risk factor, however, is prematurity. Not only is the immature digestive tract less able to protect itself, but premature infants are subjected to many stresses on the body in their attempt to survive.

Early symptoms of necrotizing enterocolitis include an intolerance to formula, distended and tender abdomen, vomiting, and blood (visible or not) in the stool. One of the earliest signs may also be the need for mechanical support of the infant's breathing. If the infection spreads to the bloodstream, infants may develop lethargy, fluctuations in body temperature, and periodically stop breathing.

Diagnosis

The key to reducing the complications of this disease is early suspicion by the physician. A series of x rays of the bowel often reveals the progressive condition, and blood tests confirm infection.

Treatment

Over two-thirds of infants can be treated without surgery. Aggressive medical therapy is begun as soon as the condition is diagnosed or even suspected. Tube feedings into the gastrointestinal tract (enteral nutrition) are discontinued, and tube feedings into the veins (parenteral nutrition) are used instead until the condition has resolved. Intravenous fluids are given for several weeks while the bowel heals.

Some infants are placed on a ventilator to help them breathe, and some receive transfusions of platelets, which help the blood clot when there is internal bleeding. Antibiotics are usually given intravenously for at least 10 days. These infants require frequent evaluations by the physician, who may order multiple abdominal x rays and blood tests to monitor their condition during the illness.

Sometimes, necrotizing enterocolitis must be treated with surgery. This is often the case when an infant's condition does not improve with medical therapy or there are signs of worsening infection.

The surgical treatment depends on the individual patient's condition. Patients with infection that has caused serious damage to the bowel may have portions of the bowel removed. It is sometimes necessary to create a substitute bowel by making an opening (ostomy) into the abdomen through the skin, from which waste products are discharged temporarily. But many physicians are avoiding this and operating to remove diseased bowel and repair the defect at the same time.

Postoperative complications are common, including wound infections and lack of healing, persistent sepsis and bowel necrosis, and a serious internal bleeding disorder known as disseminated intravascular coagulation.

Prognosis

Necrotizing enterocolitis is the most common cause of death in newborns undergoing surgery. The average mortality is 30-40%, even higher in severe cases.

Early identification and treatment are critical to improving the outcome for these infants. Aggressive nonsurgical support and careful timing of surgical intervention have improved overall survival; however, this condition can be fatal in about one-third of cases. With the resolution of the infection, the bowel may begin functioning within weeks or months. But infants need to be carefully monitored by a physician for years because of possible future complications.

About 10-35% of all survivors will eventually develop a stricture, or narrowing, of the intestine that occurs with healing. This can create an intestinal obstruction that will require surgery. Infants may also be more susceptible to future bacterial infections in the gastrointestinal tract and to a delay in growth. Infants with severe cases may also suffer neurological impairment.

The most serious long-term gastrointestinal complication associated with necrotizing enterocolitis is short-bowel, or short-gut, syndrome. This refers to a condition that can develop when a large amount of bowel must be removed, making the intestines less able to absorb certain nutrients and enzymes. These infants gradually evolve from tube feedings to oral feedings, and medications are used to control the malabsorption, diarrhea, and other consequences of this condition.

Prevention

In very small or sick premature infants, the risk for necrotizing enterocolitis may be diminished by beginning parenteral nutrition and delaying enteral feedings for several days to weeks.

Some have suggested that breast milk provides substances that may be protective, but there is no evidence that this reduces the risk of infection. A large multicenter trial showed that steroid drugs given to women in preterm labor may protect their offspring from necrotizing enterocolitis.

Key terms

Enteral nutrition — Liquid nutrition provided through tubes that enter the gastrointestinal tract, usually through the mouth or nose.

Necrosis — The death of cells, a portion of tissue, or a portion of an organ due to permanent damage of some sort, such as a lack of oxygen supply to the tissues.

Parenteral nutrition — Liquid nutrition provided through tubes that are placed in the veins.

Sepsis — The presence of pus-forming or other disease-causing organisms in the blood or tissues. Septicemia, commonly known as blood poisoning, is a common type of sepsis.

Sometimes necrotizing enterocolitis occurs in clusters, or outbreaks, in hospital newborn (neonatal) units. Because there is an infectious element to the disorder, infants with necrotizing enterocolitis may be isolated to avoid infecting other infants. Persons caring for these infants must also employ strict measures to prevent spreading the infection.

Resources

Other

Neonatology on the Web. http://www.neonatology.org.

enterocolitis /en·tero·co·li·tis/ (-ko-li´tis) inflammation of the small intestine and colon.

antibiotic-associated enterocolitis that in which treatment with antibiotics alters the bowel flora and results in diarrhea or pseudomembranous enterocolitis.

hemorrhagic enterocolitis enterocolitis characterized by hemorrhagic breakdown of the intestinal mucosa, with inflammatory cell infiltration.

necrotizing enterocolitis , pseudomembranous enterocolitis an acute inflammation of the bowel mucosa with formation of pseudomembranous plaques overlying an area of superficial ulceration, with passage of the pseudomembranous material in the feces; it may result from shock and ischemia or be associated with antibiotic therapy.

ne·cro·tiz·ing enterocolitis (n

-t

ng)

Extensive ulceration and necrosis of the ileum and colon in premature infants in the neonatal period.

necrotizing enterocolitis (NEC),

an acute inflammatory bowel disorder that occurs primarily in preterm or low-birth weight neonates, typically within the first 2 weeks of life. It is characterized by ischemic necrosis of the GI mucosa that may lead to perforation and peritonitis. The cause of the disorder is unknown, although it appears to be a defect in host defenses, with infection resulting from normal GI flora rather than from invading organisms. Also called pseudomembranous enterocolitis. See also enteritis.

observations Significant predisposing factors for the condition include prematurity, hypovolemia, respiratory distress syndrome, sepsis, an indwelling umbilical catheter, exchange transfusion, and feeding with hyperosmolar or high-caloric formulas. The condition results from a reflex shunting of blood away from the GI tract, which leads to convulsive vasoconstriction of the mesenteric vessels supplying the intestines. The diminished blood supply interferes with the normal production of mucus and with other bowel functions and results in severe necrosis with bacterial invasion of the bowel wall. Bottle-fed infants are more susceptible to the disorder, possibly because formula lacks the immunoglobulin A antibodies and macrophages found in breast milk that may protect the GI mucosa from damage and bacterial invasion. Initial symptoms, which usually develop after several days of life, include temperature instability (usually hypothermia), lethargy, poor feeding, vomiting of bile, abdominal distension, blood in the stools, and decreased or absent bowel sounds. Signs of deterioration are apnea, pallor, hyperbilirubinemia, oliguria, abdominal tenderness, and erythema and edema of the anterior abdominal wall or palpable masses, with eventual respiratory failure leading to death. Diagnosis is confirmed by x-ray visualization of the intestine or by the presence of increased peritoneal fluid or pneumoperitoneum.

interventions Treatment includes discontinuation of oral feeding, IV infusion, abdominal decompression by nasogastric suction, hydration, plasma or whole blood transfusion, and administration of broad-spectrum antibiotics (usually ampicillin, gentamicin, or kanamycin). With routine supportive management, improvement usually occurs within 48 to 72 hours. Oral feedings usually are not resumed for 10 days to 2 weeks. Total parenteral nutrition is necessary during that period. Surgical resection of the affected bowel segment may be necessary, especially if signs of intestinal perforation or peritonitis develop. If a large part of bowel is affected, an ileostomy or colostomy may be necessary. Stenosis of the involved bowel segment may present later complications.

nursing considerations The primary concern of the nurse is to observe high-risk, formula-fed infants for early symptoms of necrotizing enterocolitis, especially for difficulty in feeding, bile-stained regurgitation, bloody stools, temperature fluctuations, or a distended shiny abdomen. After the diagnosis is confirmed, the nurse initiates nasogastric intubation for abdominal decompression and continues to monitor the baby constantly for dehydration and electrolyte balance. Daily weight is taken. Infants who are unable to take fluids by mouth require special oral care. A pacifier helps meet the infant's need to suck. Parents are encouraged to visit and are helped to meet the emotional needs of the infant and to provide tactile, auditory, and visual stimulation. The nurse explains the usual course of the disease and the medical and nursing procedures and keeps the parents informed of the infant's progress. Frequent visits to the care unit facilitate family-infant relationships and provide the nurse with an opportunity to teach proper care techniques before discharge. Most infants who develop NEC recover fully and do not have further feeding problems.

necrotizing enterocolitis

Neonatology A disease of premature infants, affecting the terminal ileum 3-10 days after birth, representing 2% of neonatal ICU admissions and 10% of admissions of premature infant, or low birth weight neonates, causing significant M&M Clinical Banal to fulminant with abdominal distension, vomiting, hematochezia, intestinal gangrene, perforation, sepsis, shock; survival 80%; NEC is rare in breast-fed children, who may be protected by IgA in maternal milk; oral IgA-IgG solution in LBW infants may be protective. Cf Pigbel.