You are in: eMedicine Specialties > Radiology > PEDIATRICS Necrotizing EnterocolitisArticle Last Updated: Feb 21, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Beverly P Wood, MD, MS, PhD, Professor, Departments of Radiology and Pediatrics, Division of Medical Education, Keck School of Medicine, University of Southern California Beverly P Wood is a member of the following medical societies: American Academy of Pediatrics, American Association for Women Radiologists, American College of Radiology, American Institute of Ultrasound in Medicine, American Medical Association, American Roentgen Ray Society, Association of University Radiologists, Radiological Society of North America, and Society for Pediatric Radiology Editors: Fredric A Hoffer, MD, FAAP, FSIR, Professor of Radiology, University of Washington; Section Chief of Interventional Radiology, Department of Radiology, Seattle Children's Hospital and Regional Medical Center; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; David A Stringer, BSc, MBBS, FRCR, FRCPC, Professor, National University of Singapore; Clinical Director, Diagnostic Imaging, National University Hospital; Head, Diagnostic Imaging, KK Women's and Children's Hospital, Singapore; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; John Karani, MBBS, FRCR, Consulting Staff, Department of Radiology, King's College Hospital, London Author and Editor Disclosure Synonyms and related keywords: NEC, neonatal colitis, neonatal enteritis, necrotic appendicitis of the newborn, neonatal gastrointestinal disease, complication of prematurity INTRODUCTIONSection 2 of 10
  BackgroundNecrotizing enterocolitis (NEC) is a serious gastrointestinal disease of unknown etiology in neonates. NEC is characterized by mucosal or transmucosal necrosis of part of the intestine. Infants born before term who are undersized and ill are most susceptible to NEC; the incidence of NEC is increasing because of the improved survival rate in the high-risk group of premature infants.1, 2, 3 PathophysiologySeveral factors contribute to the development of neonatal NEC. The underlying pathology is one of gas accumulation in the submucosal layers of the bowel wall that progresses to necrosis. Eventual necrosis of the bowel loops, perforation, systemic sepsis, and death can result from NEC. The bowel regions most often affected are the right side of the colon and the distal ileum, although any portion of the bowel is susceptible. The major or most common contributor to NEC is sepsis; however, indwelling vascular catheters, assisted ventilation, respiratory acidosis, and hypoxemia are contributing factors as well. NEC is primarily a complication of premature birth with possible hypoxemia, acidosis, hypotension, sepsis, and stress. NEC can also occur in ill full-term neonates, particularly those with a history of sepsis, hypoxia, asphyxia, or difficult resuscitation. Polycythemia, the use of hypertonic formulas or medicines, and an establishment of feeding that is too rapid may cause mucosal injury. Epidemics of NEC have been documented, and infectious agents such as Clostridium perfringens, Escherichia coli, Staphylococcus epidermidis, and rotavirus have been identified in association with NEC. Most often, no pathogen is identified. FrequencyUnited StatesThe occurrence of NEC varies from isolated cases to nursery epidemics. The population group most often affected is ill, preterm neonates.4 InternationalThe incidence rates of NEC are similar in all developed countries in which premature infants can survive as a result of complicated treatment measures. Mortality/MorbidityCurrently, the mortality rate of NEC is less than 20% when infants with NEC are identified and treated early in the illness. Without treatment, the mortality rate is extremely high. Morbidity associated with NEC includes bowel stricture, peritoneal adhesions, and bowel perforation. If perforation occurs, the necrotic bowel is surgically resected. Resection of large lengths of bowel may result in short-bowel syndrome.5 SexNEC exhibits no sexual predilection. AgeThe incidence in premature neonates is highest in those with very low birth weights.6 NEC is less commonly seen in premature neonates with higher birth weights and in full-term neonates. AnatomyThe distal ileum and proximal colon are most commonly involved in NEC, although any region of the bowel may be involved. The stomach can be involved as well. Clinical DetailsThe onset of NEC can occur from 2 weeks to several months after birth. Meconium is usually passed normally, and the initial signs of NEC include abdominal distention and gastric retention of fluid. Manifestations of the disease develop after enteric feedings begin. Obviously bloody stool is observed in approximately 25% of patients. The onset of NEC can be insidious, and sepsis may occur before any intestinal abnormality is noted. The spectrum of presentations ranges from mild NEC with guaiac-positive stool to severe NEC with peritonitis, bowel perforation, shock, and possible death. The progression of NEC may be rapid; however, progression of the disease after 72 hours is usual. Pneumatosis is a late finding in NEC and usually indicates some necrosis of the bowel wall. The presence of irritability and bowel distention, especially when associated with bloody stool, is diagnostic of NEC. Preferred ExaminationInfants with suspected NEC should undergo periodic radiography of the abdomen. In some centers, infants in whom NEC is highly suspected undergo routine frontal abdomen radiography every 4-6 hours. Cross-table lateral examinations with a horizontal beam are useful for detecting subtle, early collections of free air (see Images 5-7), although some clinicians prefer to use lateral decubitus radiographs to detect free air. In the presence of peritoneal adhesions, keeping the patient in the decubitus position for a prolonged time ensures that the air moves to the highest point. Limitations of TechniquesSmall amounts of free air may not be easily visible on supine abdominal radiographs. Also, thickening of bowel wall may not be easily observed in the presence of a dilated bowel. DIFFERENTIALSSection 3 of 10
Other Problems to Be ConsideredObstruction resulting from tenacious intestinal content in infants who are fed high-energy formulas RADIOGRAPHSection 4 of 10
FindingsA high index of suspicion is essential for the diagnosis of NEC. Abdominal radiographs may demonstrate multiple dilated bowel loops that change little in their location and appearance with sequential studies. Pneumatosis intestinalis, or gas in the bowel wall with a linear or bubbly pattern (see Images 1-4), is present in 50-75% of patients. Portal venous gas and gallbladder gas are indicative of serious disease. Pneumoperitoneum indicates a bowel perforation. Computed tomography (CT) scanning or a water-soluble enema examination (see Image 8) may be used to demonstrate pneumatosis or a site of perforation. Degree of ConfidenceRadiography is sufficient for an accurate diagnosis of NEC, and the presence of air on a horizontal-beam radiograph is sufficient to diagnose a bowel perforation. CT SCANSection 5 of 10
FindingsThe use of CT is not advocated in the diagnosis of NEC or free air. CT scanning or an examination with a water-soluble enema may be used to demonstrate pneumatosis or a site of perforation. ULTRASOUNDSection 6 of 10
FindingsUltrasonography of the abdomen characteristically shows thick-walled loops of bowel with hypomotility. Intraperitoneal fluid is often present. In the presence of pneumatosis intestinalis, gas is identified in the portal venous circulation within the liver. INTERVENTIONSection 7 of 10
The presence of free air indicates a bowel perforation; in this case, surgical exploration and resection of necrotic bowel is needed. Intensive therapy is started immediately, and feeding is stopped, nasogastric decompression is performed, and intravenous fluids are administered. Once cultures of blood, stool, and cerebrospinal fluid are obtained, systemic antibiotics are started; these may include anti-Pseudomonas medications and an aminoglycoside.7 When present, umbilical catheters are removed, and assisted ventilation should be initiated if distention contributes to hypoxia. If hypotension develops, resuscitation is initiated with the administration of blood, plasma, crystalloid, and/or dopamine, as indicated. The patient's course is monitored with frequent radiography, including cross-table lateral views, to evaluate perforation. Medical treatment fails in approximately 20% of patients with associated pneumatosis intestinalis. Pneumatosis intestinalis is lethal in at least 25% of these patients. Strictures develop at the site of the necrotizing lesion in approximately 10% of patients. Resection of the stricture is curative. Complications that can occur after massive intestinal resection include short-bowel syndrome, cholestatic jaundice, and conditions related to total parenteral alimentation via central venous catheters.5 Complications may be prevented with judicious feeding and the use of breast milk. FURTHER READINGSection 8 of 10
For more information on necrotizing enterocolitis, see Current Controversies in the Understanding of Necrotizing Enterocolitis, Surgical Intervention for the Treatment of Necrotizing Enterocolitis, and Color Doppler Ultrasound May Be Helpful in Diagnosing Necrotizing Enterocolitis, available on Medscape. MULTIMEDIASection 9 of 10
REFERENCESSection 10 of 10
Necrotizing Enterocolitis excerpt Article Last Updated: Feb 21, 2008 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
