Lynn Ramirez-Avila, HMS IV

Gillian Lieberman, MD

The Radiologic Manifestations of Necrotizing Enterocolitis

Lynn Ramirez-AvilaHarvard Medical School Year IV

Gillian Lieberman, MD

September 2003

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Baby R

• Former 28.5 weeker with episodes of respiratory distress in the first days of life

• On day of life 8 Baby R started full feeds

• On day of life 8 Baby R developed marked abdominal distension & guaiac positive stools

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Objectives

• Overview of necrotizing enterocolitis

• Overview of common radiologic findings in nectrotizing enterocolitis

• Review the future role of imaging modalities in diagnosing necrotizing enterocolitis

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Necrotizing Enterocolitis (NEC)

• Is the necrosis of the mucosa or submucosa of any portion of the GI tract

• Affects predominantly preterm & low birth weight infants

• Other risk factors include:– Compromise of mucosal integrity & bowel integrity– Compromised mesenteric blood supply– Changes in bowel lumen

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Pathophysiology• Multifactorial process that usually affects terminal ileum

and right colon

• Exact pathophysiologic mechanism is not known, but it is thought that:

• Bacterial colonization• Intestinal hypoxia • Formula feeding

Activation of proinflammatory

mediators & subsequently bowel

necrosis

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Arterial Supply of the ColonSuperior Mesenteric Artery

Ileocolic, Right colic, Superior Mesenteric Arteries

Norman W, http://mywebpages.comcast.net/wnor/smlintestinebloodsupply.jpg

Terminal Ileum, Cecum, Right Colon

Venous Tributaries

Superior Mesenteric Vein

Hepatic Portal Vein

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Clinical Presentation

• Usually occurs in days 3-10 of life

• Systemic symptoms include:– Apnea, bradycardia, temperature instability, lethargy,

poor feeding

• Gastrointestinal symptoms include: – Diarrhea, abdominal distention, gastric retention,

gasterointestinal bleeding

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

BELL CriteriaStage Clinical Signs

I (Suspected) Abdominal distension, poor feeding, vomiting

II (Definite) Abdominal distension, poor feeding, vomiting, GI bleeding

III (Advanced) Abdominal distension, poor feeding, vomiting, GI bleeding &

septic shock

Summarized from Rencken et al, 1997

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Imaging Modalities• Radiologic imaging is key to diagnosis and

monitoring

• If NEC is suspected, abdominal films are obtained every 12-24 hours

• Supine abdominal, cross table lateral view, or left-side-down decubitus are standard

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Plain films and Bell CriteriaStage Clinical

SignsRadiologic Findings

I (Suspected) Abdominal distension, poor feeding, vomiting

Ileus

II (Definite) Abdominal distension, poor feeding, vomiting, GI bleeding

Intestinal pneumatosis & portal venous air

III (Advanced) Abdominal distension, poor feeding, vomiting, GI bleeding & septic shock

Ileus, intestinal pneumatosis, portal venous air,

pneumoperitoneum

Summarized from Rencken et al, 1997

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Normal Neonatal Abdominal Radiograph

• Liver is prominent in pediatric abdominal films

• Difficult to discern the small from large intestine

• Bowel gas pattern bordering the liver is likely to be the transverse colon

• Bowel gas pattern in the lower pelvic region likely to be the rectum

Courtesy Dr. W. Durgin, BIDMC

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Radiography & Stage I NEC

• Nonspecific radiographic findings:

– Diffuse gaseous distension of intestine

– Loss of normal bowel gas pattern symmetry

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Bowel Distension

From Buonomo, C. 1999. Imaging of neonatal gastrointestinal obstruction. Rad Clin North America, 37(6): 1187-98.

• Occurs in the small intestine, colon, or both

• Distension of the small intestine often occurs 4-48 hours before the onset of clinical signs

• Distension of large colon occurs in 30% of NEC patients

• This is a relatively non-specific sign

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Bowel Distension Radiographic Differential

– Meconium Ileus

– Total Colonic Anganlionosis

– Mid-gut volvulus

– Gastroenteritis, peritonitis, sepsis

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Abnormal Gas Distribution

From Buonomo, C. 1999. Imaging of neonatal gastrointestinal obstruction. Rad Clin North America, 37(6): 1187-98.

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Radiology & Stage II NEC

• Pneumatosis intestinalis is essentially pathognomonic for NEC

• Portal venous gas is correlated with worse prognosis

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Pneumatosis Intestinalis

Courtesy of Dr. Makris, Children’s Hospital Boston

• Intramural Air

• Focal versus diffuse

• Air can be located in the

- Submucosa

Bubbly/cystic

- Subserosa

Linear/curvilinear

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Pneumatosis Intestinalis (continued)

Courtesy of Dr. Makris, Children’s Hospital Boston

Radiographic Differential

•In combination with dilated bowel indicative of NEC

•Feces

•Milk impaction secondary to onset of feeding

•Benign pneumatosis from extension from air in the mediastinum

•Congenital obstruction (atresias, imperforate anus, meconium plug, etc.

•Hirschsprung’s

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Portal Venous Gas (PVG)

• Associated with severe NEC and babies with PVG have worst outcomes

• Visualized better on cross table lateral view

• On ultrasound PVG is seen as moving echogenicity in portal vein

Courtesy Dr. W. Durgin, BIDMC

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

PVG (continued)

http://www.hawaii.edu/medicine/pediatrics/neoxray/neoxray.html

Radiographic Differential

•Iatrogenic via umbilical vein catheters

•Air in biliary tree secondary to duodenal atresia with incompetent Sphincter of Oddi

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Radiology & Stage III NEC• Persistent (sentinel) loop sign

• Asymmetric bowel dilatation

• Ascites

• Pneumoperitoneum

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Persistent Loop Sign (Sentinel Loop)

• Is the persistence of a dilated loop of bowel on subsequent radiographs for 24 to 36 hours

From Buonomo, C. 1999. Imaging of neonatal gastrointestinal obstruction. Rad Clin North America, 37(6): 1187-98

Radiographic Differential

•Appendicitis

•Paralytic Ileus

•Pancreatitis

•Drug-induced

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Pneumoperitoneum

http://bms.brown.edu/pedisurg/Brown/Image%20bank%20pages/NEC.html

Radiographic Differential

•Idiopathic perforation

•Focal intestinal perforation

•Intestinal obstruction

•Iatrogenic (puncture with nasogastric tube)

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Baby R

• Baby gram radiographic findings:

- Distended bowel loops

-Pneumatosis intestinalis

- Free Air under the left diaphragm

Courtesy of Dr. Makris, Children’s Hospital Boston

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Treatment of NEC• Clinical Management

– Discontinue feeds– IV fluids– Gastric decompression via NG tube– Total parenteral nutrition– Broad-spectrum antibiotics

• Surgical Management– Indications include pneumoperitoneum, sentinel loops,

ascites, or worsening clinical picture

– Resection of the necrotic bowel, proximal enterostomy, with subsequent reanastomosis at a later time

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Outcome of Baby R

•Underwent exploratory laparotomy

•Subsequently had right hemicolectomy with ileocecal valve resection

• Follow-up radiograph is shown

Courtesy of Dr. Makris, Children’s Hospital Boston

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Chronic Complications of NEC

• Usually occurs a few weeks after acute disease

• Radiographic follow-up conducted for 2 years

• Course can be complicated by NEC strictures, bowel obstruction, enterenterofistulae, enterocysts

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Post-NEC Stricture•Single or multiple strictures occur

•Commonly occur in the left colon

• Spontaneous resolution of NEC strictures occurs

• Routine barium enemas are performed in children who undergo surgery, but not in children who have had medical management of NEC

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

NEC Strictures

From Buonomo, C. 1999. Imaging of neonatal gastrointestinal obstruction. Rad Clin North America, 37(6): 1187-98

From Rabinowitz, JG. “Radiographic Manifestations” in Neonatal Necrotizing Enterocolitis, Brown EG, Sweet AY eds. 1980

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

NEC & other Imaging Modalities• Abdominal plain radiographs are

nonspecific in the early and late stages of NEC

• The use of computed tomography in NEC diagnosis has been explored

• Use of MRI in NEC diagnosis is under study

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

NEC & CT

• The permeation of contrast administered into ischemic bowel has been reported in animal models of NEC

• The contrast is resorbed from the peritoneum & is excreted into the urinary system

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

NEC & CT (continued)• Study included babies with NEC and controls (n=22) who were orally

given non-ionic contrast

• After contrast administration, they collected the urine of babies with NEC and controls and CT the urine

• They found that after contrast, the urine of babies with suspected and definite NEC have higher Hounsfield Units than controls

ControlUrine

Urine of babies who underwent other GI

study

Urine of babies with suspected NEC

Urine of babies with definite NEC

5.6 HU +/- 3.9 6.7 HU +/- 3.2 26.0 HU +/- 3.4 71.0 HU +/- 18.8

summarized from Rencken et al, 1997

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

NEC & MRI• Maalouf et al report MRI findings of NEC amongst a

group of low birth weight and preterm infants and their controls

• They conclude that the following characteristics were associated with severe forms of NEC: – Fluid levels within lumen– Intramural gas– Bubble-like appearance in bowel wall

• Bowel areas with a bubble-like appearance corresponded to areas of bowel that were surgically resected

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

NEC & MRI

From Maalouf: Pediatrics, Volume 105(3).March 2000.510-514

Bubble-like Appearance Air-fluid levels

Intramural Air

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

NEC & Ultrasound

From Kodroff et al, 1984

Pseudo-kidney sign

• Non-specific sign seen in any process where blood, pus, fluid, tumor invades bowel wall

• Necrotic bowel cannot be distinguished from inflammatory bowel disease

•Given, demographics of preterm population, this sign is most consistent with NEC

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Portal Venous Gas & Ultrasound

Right Upper Quadrant

U/SLiver Ultrasound of Neonate with NEC

From Merrit et al, 1984

Echogenicities in liver parenchyma

Microbubble in portal veinNormal Ultrasound

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Conclusion• The incidence of NEC is increasing secondary to

increased survival of low-birth weight and pre- term infants

• Diagnostic imaging, specifically plain films are important in the diagnosis, progression, and follow-up of NEC

• But, secondary to the sensitivity of current abdominal plain films, the use of CT, MRI, and U/S could provide a more sensitive and specific imaging alternative

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

References• Brown University Department of Pediatric Surgery http://bms.brown.edu/pedisurg/Brown/Image%20bank%20pages/NEC.html

• Buonomo C (1999). The Radiology of Necrotizing Enterocolitis in Neonatal Imaging Rad Clin North America 37: 1999.

• Caplan MS, Jilling T (2001). New Concepts in necrotizing enterocolitis. Curr Opin Ped 13: 111.

• Kodroff MB, Hartenberg, MA, Goldschmidt RA (1984). Ultrasonographic diagnosis of gangrenous bowel in neonatal necrotizing enterocolitis. Ped Rad 14: 168.

• Fotter R, Sorantin (1994). Diagnostic imaging in necrotizing enterocolitis. Acta Paed Supp 398: 41.

• Kodroff MB, Hartenberg, MA, Goldschmidt RA (1984). Ultrasonographic diagnosis of gangrenous bowel in neonatal necrotizing enterocolitis. Pediatr Radiol 14: 168.

• Merritt CRB, Goldsmith JP, Sharp MJ. (1984) Sonographic Detection of Portal Venous Gas in Infants with Necrotizing Enterocolitis. AJR 143: 1059.

• Maalouf EF, Fagbemi A, Duggan PJ, Jayanthi S, Counsell SJ, Lewis HJ, Fletcher AM, Lakhoo K, Edwards AD. (2000) Magnetic Resonance Imaging of Intestinal Necrosis in Preterm Infants. Pediatrics 105: 510.

• Norman, W. Superior Mesenteric Artery Ilustration available [Online] http://mywebpages.comcast.net/wnor/smlintestinebloodsupply.jpg. September 10, 2003.

• Rabinowitz, JG. (1980). Radiographic Manifestations in Monographs in Neonatology: Neonatal Necrotizing Enterocolitis Brown EG, Sweet AY (eds). New York: Grune and Stratton.

• Reeder MM, WG Bradley (2001). Reeder and Felson’s Gamuts in Radiology: Comprehensive List of Roentgen Differential Diagnosis. New York: Springer Verlag Publishing.

• Renken IO, Sola A, Al-Ali F, Solano JP, Goldbergt HI, Cohen PA, Gooding CA. (1997). Necrotizing Enterocolitis: Diagnosis with CT Examination of Urine after Enteral Administration of Iodinated Water-soluble Contrast Material. Ped Radiology 205: 87.

• Schanler RJ. (2003). Up to Date: Clinical features and treatment of necrotizing enterocolitis in newborns available [Online] www.uptodate.com September 10, 2003.

• Wood BP. (2002). E medicine: Necrotizing Enterocolitis available [Online]: http://www.emedicine.com/radio/topic469.htm.

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Lynn Ramirez-Avila, HMS IV Gillian Lieberman, MD

Acknowledgements

• Dr. J. Makris, Children’s Hospital Boston• Dr. W. Durgin, BIDMC• Dr. G. Lieberman, BIDMC• Pamela Lepkowski• Larry Barbaras, BIDMC Webmaster