Necrotizing enterocolitis
Encyclopedia
Necrotizing enterocolitis (NEC) is a medical condition primarily seen in premature
infant
s, where portions of the bowel undergo necrosis
(tissue death).
. More recently ultrasonography has proven to be useful as it may detect signs and complications of NEC before they are evident on radiographs. Diagnosis is ultimately made in 5-10% of very low-birth-weight infants (<1,500g). However, it is not known whether some underlying pathology contributes to premature birth and low birth weight
.
The clinical features are divided into 3 stages:
Stage 1 - Apnea, bradycardia, lethargy, abdominal distension and vomiting.
Stage 2 - Pneumatosis intestinalis and the above features.
Stage 3 - Low blood pressure, bradycardia, acidosis, disseminated intravascular coagulation (DIC) and anuria.
, which may be able to be reversed at a later time. Some children may suffer later as a result of short bowel syndrome
if extensive portions of the bowel had to be removed.
s (NICUs) have been seen, but no common organism has been identified. Pseudomonas aeruginosa
is suspected for causing necrotising enterocolitis in premature infants and neutropaenic cancer patients, often secondary to gut colonisation. A combination of intestinal flora, inherent weakness in the neonatal immune system, empirical
antibiotic use for 5 days or more, alterations in mesenteric
blood flow and milk feeding may be factors. The most common area of the bowel affected by NEC is near the ileocecal valve (the site of transition between the small and large bowel). NEC is almost never seen in infants before oral feedings are initiated. Formula feeding increases the risk of NEC by tenfold compared to infants who are fed breastmilk alone. Expressed breast milk protects the premature infant not only by its antiinfective effect and its immunoglobulin agents but also from its rapid digestion.
A study by the Neonatal Research Network, published in the journal Pediatrics in January 2009, conducted a study regarding the administration of empirical antibiotics in extremely low birth weight infants. The research demonstrated that empirical antibiotic therapy over 5 days for extremely low birth weight babies increased the chance of necrotizing enterecolitis by 4% for each additional day over 5 days.
(fats and/or oils) infusion for very low birth weight infants in the first week of life resulted in zero infants developing NEC in the experimental group, compared with 14 % with NEC in the control group (They started the experimental group at 2 g/kg/d of 20% IVFE and increased within two days to 3 g/kg/d; Amino acids were started at 3 g/kg/d and increased to 3.5). (Drenckpohl D, McConnell C, Gaffney S, Niehaus M, Macwan KS. Randomized trial of very low birth weight infants receiving higher rates of infusion of lipid emulsions during the first week of life Pediatrics 2008;122;743-751).
Neonatologists at the University of Iowa NICU reported on the importance of providing small amounts of trophic oral feeds of human milk starting ASAP, while the infant is being primarily fed intravenously, in order to prime the immature gut to mature and become ready to receive greater oral intake (Ziegler and Carlson, J Matern Fetal Neonatal Med. 2009 Mar;22(3):191-7.) Human milk from a milk bank or donor can be used if mother's milk is unavailable. The gut mucosal cells do not get enough nourishment from arterial blood supply to stay healthy, especially in very premature infants, where the blood supply is limited due to immature development of the capillaries, so nutrients from the lumen of the gut are needed.
Despite a significant mortality risk, long-term prognosis for infants undergoing NEC surgery is improving, with survival rates of 70-80%. "Surgical NEC" survivors are at-risk for complications including short bowel syndrome
, and neurodevelopmental disability.
Premature birth
In humans preterm birth refers to the birth of a baby of less than 37 weeks gestational age. The cause for preterm birth is in many situations elusive and unknown; many factors appear to be associated with the development of preterm birth, making the reduction of preterm birth a challenging...
infant
Infant
A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...
s, where portions of the bowel undergo necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
(tissue death).
Signs and symptoms
The condition is typically seen in premature infants, and the timing of its onset is generally inversely proportional to the gestational age of the baby at birth, i.e. the earlier a baby is born, the later signs of NEC are typically seen. Initial symptoms include feeding intolerance, increased gastric residuals, abdominal distension and bloody stools. Symptoms may progress rapidly to abdominal discoloration with intestinal perforation and peritonitis and systemic hypotension requiring intensive medical support.Diagnosis
The diagnosis is usually suspected clinically but often requires the aid of diagnostic imaging modalities. Radiographic signs of NEC include dilated bowel loops, paucity of gas, a "fixed loop" (unaltered gas-filled loop of bowel), pneumatosis intestinalis, portal venous gas, and pneumoperitoneum (extraluminal or "free air" outside the bowel within the abdomen). The pathognomic finding on plain films is pneumatosis intestinalisPneumatosis intestinalis
In radiology, pneumatosis intestinalis is a sign on x-ray which is highly suggestive for necrotizing enterocolitis.It refers to gas cysts in the bowel wall. This is in contrast to gas in the lumen which is normal.-References:...
. More recently ultrasonography has proven to be useful as it may detect signs and complications of NEC before they are evident on radiographs. Diagnosis is ultimately made in 5-10% of very low-birth-weight infants (<1,500g). However, it is not known whether some underlying pathology contributes to premature birth and low birth weight
Low birth weight
Low birth weight is defined as a birth weight of a liveborn infant of less than 2,500 g. regardless of gestational age-Causes:LBW is either the result of preterm birth or of the infant being small for gestational age , or a combination of...
.
The clinical features are divided into 3 stages:
Stage 1 - Apnea, bradycardia, lethargy, abdominal distension and vomiting.
Stage 2 - Pneumatosis intestinalis and the above features.
Stage 3 - Low blood pressure, bradycardia, acidosis, disseminated intravascular coagulation (DIC) and anuria.
Treatment
Treatment consists primarily of supportive care including providing bowel rest by stopping enteral feeds, gastric decompression with intermittent suction, fluid repletion to correct electrolyte abnormalities and third space losses, support for blood pressure, parenteral nutrition, and prompt antibiotic therapy. Monitoring is clinical, although serial supine and left lateral decubitus abdominal roentgenograms should be performed every 6 hours. Where the disease is not halted through medical treatment alone, or when the bowel perforates, immediate emergency surgery to resect the dead bowel is generally required, although abdominal drains may be placed in very unstable infants as a temporizing measure. Surgery may require a colostomyColostomy
A colostomy is a surgical procedure in which a stoma is formed by drawing the healthy end of the large intestine or colon through an incision in the anterior abdominal wall and suturing it into place. This opening, in conjunction with the attached stoma appliance, provides an alternative channel...
, which may be able to be reversed at a later time. Some children may suffer later as a result of short bowel syndrome
Short bowel syndrome
Short bowel syndrome is a malabsorption disorder caused by the surgical removal of the small intestine, or rarely due to the complete dysfunction of a large segment of bowel. Most cases are acquired, although some children are born with a congenital short bowel...
if extensive portions of the bowel had to be removed.
Cause
NEC has no definitive known cause. An infectious agent has been suspected, as cluster outbreaks in neonatal intensive care unitNeonatal intensive care unit
A Neonatal Intensive Care Unit —also called a Special Care Nursery, newborn intensive care unit, intensive care nursery , and special care baby unit —is an intensive care unit specializing in the care of ill or premature newborn infants.The problem of premature and congenitally ill infants is not a...
s (NICUs) have been seen, but no common organism has been identified. Pseudomonas aeruginosa
Pseudomonas aeruginosa
Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...
is suspected for causing necrotising enterocolitis in premature infants and neutropaenic cancer patients, often secondary to gut colonisation. A combination of intestinal flora, inherent weakness in the neonatal immune system, empirical
Empiric therapy
Empiric therapy is a medical term referring to the initiation of treatment prior to determination of a firm diagnosis. It may be thought of as taking the initiative against an anticipated and likely cause of infectious disease. It is most often used when antibiotics are given to a person before the...
antibiotic use for 5 days or more, alterations in mesenteric
Mesentery
In anatomy, the mesentery is the double layer of peritoneum that suspends the jejunum and ileum from the posterior wall of the abdomen. Its meaning, however, is frequently extended to include double layers of peritoneum connecting various components of the abdominal cavity.-Mesentery :The...
blood flow and milk feeding may be factors. The most common area of the bowel affected by NEC is near the ileocecal valve (the site of transition between the small and large bowel). NEC is almost never seen in infants before oral feedings are initiated. Formula feeding increases the risk of NEC by tenfold compared to infants who are fed breastmilk alone. Expressed breast milk protects the premature infant not only by its antiinfective effect and its immunoglobulin agents but also from its rapid digestion.
A study by the Neonatal Research Network, published in the journal Pediatrics in January 2009, conducted a study regarding the administration of empirical antibiotics in extremely low birth weight infants. The research demonstrated that empirical antibiotic therapy over 5 days for extremely low birth weight babies increased the chance of necrotizing enterecolitis by 4% for each additional day over 5 days.
Prevention
Once a child is born prematurely, thought must be given to decreasing the risk for developing NEC. Toward that aim, the methods of providing hyperalimentation and oral feeds are both important. A recent study, by researchers in Peoria, IL, published in Pediatrics in 2008, demonstrated that using a higher rate of lipidLipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
(fats and/or oils) infusion for very low birth weight infants in the first week of life resulted in zero infants developing NEC in the experimental group, compared with 14 % with NEC in the control group (They started the experimental group at 2 g/kg/d of 20% IVFE and increased within two days to 3 g/kg/d; Amino acids were started at 3 g/kg/d and increased to 3.5). (Drenckpohl D, McConnell C, Gaffney S, Niehaus M, Macwan KS. Randomized trial of very low birth weight infants receiving higher rates of infusion of lipid emulsions during the first week of life Pediatrics 2008;122;743-751).
Neonatologists at the University of Iowa NICU reported on the importance of providing small amounts of trophic oral feeds of human milk starting ASAP, while the infant is being primarily fed intravenously, in order to prime the immature gut to mature and become ready to receive greater oral intake (Ziegler and Carlson, J Matern Fetal Neonatal Med. 2009 Mar;22(3):191-7.) Human milk from a milk bank or donor can be used if mother's milk is unavailable. The gut mucosal cells do not get enough nourishment from arterial blood supply to stay healthy, especially in very premature infants, where the blood supply is limited due to immature development of the capillaries, so nutrients from the lumen of the gut are needed.
Prognosis
Typical recovery from NEC if medical, non-surgical treatment succeeds, includes 10–14 days or more without oral intake and then demonstrated ability to resume feedings and gain weight. Recovery from NEC alone may be compromised by co-morbid conditions that frequently accompany prematurity. Longterm complications of medical NEC include bowel obstruction and anemia.Despite a significant mortality risk, long-term prognosis for infants undergoing NEC surgery is improving, with survival rates of 70-80%. "Surgical NEC" survivors are at-risk for complications including short bowel syndrome
Short bowel syndrome
Short bowel syndrome is a malabsorption disorder caused by the surgical removal of the small intestine, or rarely due to the complete dysfunction of a large segment of bowel. Most cases are acquired, although some children are born with a congenital short bowel...
, and neurodevelopmental disability.
External links
- Pictures of Necrotizing Enterocolitis at MedPix