How Often Does Pneumatosis Intestinalis Occur with NEC?

Patient Presentation
A 38-day old male, former 29-week premature infant was doing well weaning off mechanical ventilation.
He was not on antibiotics but had a previous suspected sepsis episode.
He was receiving intravenous fluids and 1/3 of his fluids by nasogastric enteral feedings with breastmilk plus human milk fortifier.
He was not having any apnea or bradycardia spells.
The nursing staff noted that he had a bloody stool, where the blood was mixed into the stool and on top of the stool.
The review of systems was otherwise negative.
The pertinent physical exam showed a weight of 1.465 grams, heart rate = 188 beats/minute, respiratory rate of 66 breaths/minute, and blood pressure of 77/48. His vital sign trends were unchanged.
HEENT showed an anterior fontanelle that was soft, open and flat.
Lungs were without adventitial breath sounds and no increased work of breathing.
Heart was regular rate and rhythm without a murmur.
Abdomen was soft, nontender, rounded with hypoactive bowel sounds present. No masses were palpable or abnormal skin coloring of the abdomen or flanks.
Neurological examination showed normal tone, strength and moving all extremities appropriately.
The work-up included a complete blood count that showed an increased white blood cell count of 16.5 x 1000/mm2 and platelet count of 625 x 1000/mm2. A C-reactive protein, and urinalysis were negative.
The radiologic evaluation showed thickened small bowel loops with pneumatosis intestinalis predominantly in the left lower quadrant. No portal venous gas or free air was noted.
The diagnosis of necrotizing enterocolitis with pneumatosis intestinalis was made.
Antibiotics were begun, enteral feedings were stopped and surveillance abdominal radiographs were ordered.
The patient’s clinical course revealed that he received 10 days of antibiotics and never had clinical evidence of sepsis or other deterioration in his condition.
His blood, urine and stool cultures were negative for bacteria and enteroviral cultures Clostridium difficile toxin were also eventually negative. His hematochezia resolved in 2-3 days. He continued to wean off his ventilator settings and nasogastric feedings were resumed.


Figure 62 – AP supine radiograph of the abdomen demonstrates pneumatosis intestinalis in the left lower quadrant, consistent with a diagnosis of necrotizing enterocolitis. There was no evidence of free air or portal venous gas.

Discussion
Necrotizing enterocolitis (NEC) is unfortunately a common acute life threatening disease for infants. The terminal ileum is the most common area affected by NEC.
It is a clinical entity where the patient has feeding intolerance, blood in the stools and radiographic changes.
Patients with NEC often show abdominal distension, feeding intolerance (i.e. emesis, increased residual nasogastric feedings, bilious emesis or bilious residuals), blood in the stool, erythema or other abdominal/flank skin color changes and lethargy.
Clinically, patients may also have difficulty with ventilation, apnea, bradycardia, bruising or bleeding problems, hypotonia, and decreased stooling.
Radiographically patients may have focal but non-specific bowel loop distension, edematous thickening of the bowel wall, fixed dilated bowel loops indicating lack of peristalsis and possible necrosis, pneumatosis intestinalis, portal venous gas, or free intraperitoneal air from perforation.
Laboratory testing may show evidence of metabolic acidosis, coagulopathy, increased inflammatory markers such as C-reactive protein and increased stool reducing substances from carbohydrate intolerance. NEC can be relatively mild or severe with sepsis

NECs exact cause still is not elucidated and most likely multifactorial. The most widely accepted risk factors are prematurity, enteral feeding, bacterial colonization and mucosal injury. But how each of these factors initiates, continues or contributes to NEC is not completely elucidated.

  • Prematurity is a fairly consistent factor with 5-10% of infants < 1500 gram birth weight developing NEC. The incidence of NEC decreases with gestational age and full term infants can have NEC.
  • Enteral feedings have almost always begun when NEC occurs. NEC often occurs temporally around changes in feedings (i.e. advancement, re-initiation). Use of human milk appears to decrease the incidence of NEC but does not eliminate it.
  • Bacterial colonization occurs within 12-24 hours after birth; nitially with maternal vaginal flora and then that of external environment. Lactobacilli and Bifidobacterium are normal commensal bacteria that colonize weeks later. Overgrowth of a pathogen is implicated as part of the NEC pathogenesis but one single pathogen has not been identified. Gram-negative bacteria are most common but gram-positive bacteria, viruses and yeast also are involved.
  • Ischemia of the gastrointestinal tract is a factor. It may be an initial inciting event that eventually leads to NEC (i.e. ischemia causing mucosal edema, inflammation, etc.) or the end result (i.e. initial event causes mucosal edema, inflammation, etc. which then decreases the tissue perfusion and oxygenation).
  • Inflammatory response, especially activation of the cytokine cascade, also appears to be a factor. Platelet activating factor is one of the most studied mediators.

Learning Point
Pneumatosis intestinalis is an imaging sign and not a diagnosis itself. It is defined as abnormal gas in the gastrointestinal tract wall. In infants, it can also be caused by intestinal atresia, midgut volvulus and Hirschsprung’s disease with enterocolitis.
It is most commonly seen in the small intestine but can be found in all areas of the gastrointestinal tract from esophagus to rectum and can be seen in all ages from infancy to adulthood.

In premature infants who develop NEC, pneumatosis intestinal is found ~50% of the time. Therefore if it is seen, it helps to diagnose NEC; some infants may have NEC but not pneumatosis intestinalis.
Pneumatosis intestinalis may not be seen on the initial abdominal radiograph but serial radiographs may eventually show this finding.

Questions for Further Discussion
1. How common is NEC in full term infants?
2. How quickly should preterm infants have their enteral feedings increased?
3. What is the potential role of probiotics in the treatment of NEC?
4. What surgical techniques are used for treatment of NEC?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Information prescriptions for patients can be found at MedlinePlus for this topic: Premature Babies

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

Rudolph CD, et.al. Rudolph’s Pediatrics. 21st edit. McGraw-Hill, New York, NY. 2003:140-143.

Kim WY, Kim WS, Kim IO, Kwon TH, Chang W, Lee EK. Sonographic evaluation of neonates with early-stage necrotizing enterocolitis.
Pediatr Radiol. 2005 Nov;35(11):1056-61. Epub 2005 Aug 3.

Kawase Y, Ishii T, Arai H, Uga N. Gastrointestinal perforation in very low-birthweight infants.
Pediatr Int. 2006 Dec;48(6):599-603.

Duran R, Vatansever U, Aksu B, Acunas B. Gastric pneumatosis intestinalis: an indicator of intestinal perforation in preterm infants with necrotizing enterocolitis?
J Pediatr Gastroenterol Nutr. 2006 Oct;43(4):539-41.

Gibbs K, Lin J, Holzman IR. Necrotising Enterocolitis: The State of the Science. Indian J Pediatr 2007;74:67-72.
Available from the Internet at http://www.ijppediatricsindia.org/text.asp?2007/74/1/67/30401 (rev. 2007, cited 4/21/08).

Duran R, Vatansever U, Aksu B, Acunas B. Gastric pneumatosis intestinalis: an indicator of intestinal perforation in preterm infants with necrotizing enterocolitis?
J Pediatr Gastroenterol Nutr. 2006 Oct;43(4):539-41.

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    7. All medical and invasive procedures considered essential for the area of practice are competently performed.
    8. Health care services aimed at preventing health problems or maintaining health are provided.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.

  • Systems Based Practice
    23. Differing types of medical practice and delivery systems including methods of controlling health care costs and allocating resources are known.
    24. Cost-effective health care and resource allocation that does not compromise quality of care is practiced.

    Author
    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital

    Date
    June 13, 2008