Educational Objective:
Discuss radiological diagnosis of NEC.
Key Point:
Portal venous gas plus pneumatosis intestinalis are pathognomonic findings of NEC on plain abdominal radiographs.
Explanation:
NEC is the single most common GI emergency in neonates, affecting up to 4000 US infants every year. NEC usually develops 2-3 days following birth, with 90% developing within the first 10 days of life. The incidence is inversely proportional to gestational age, with 90% occurring in premature infants.
Pneumatosis intestinalis can appear like railroad tracks along the small bowel wall due to the presence of intramural air; railroad tracks are present in 75% of cases of NEC.
Portal venous gas appears as gas bubbles within the portal venous system and is less commonly seen (10%-30% of cases). Together, these two signs are the most specific signs for NEC, with pneumatosis intestinalis being pathognomonic for NEW and portal venous gas further strengthening the diagnosis.
Unfortunately, these strong indicators of NEW - portal venous gas plus pneumatosis intestinalis - are subtle, easily missed, and have poor interobserver reliability. In addition, these signs only occur during the later stages of NEC. This means that overall, radiographs have an overall poor sensitivity for detecting NEC at various stages, even though plain film of the abdomen remains method in which NEC is diagnosed most often
Bowel perforation frequently occurs with NEC and leads to pneumoperitoneum; however, this is not a specific sign for NEC. Absence of bowel gas, ileus or obstruction patterns can also occur with NEC, but these again are less specific.
Newer studies have found an ultrasound of the abdomen to be a helpful adjunct study that is highly specific for NEC. However, so far ultrasound has not been widely incorporated into the work-up of NEC.
References:
Kim JH. Role of Abdominal US in Diagnosis of NEC. Clin Perinatol. 2019 Mar;46(1):119-127.
Maloney PJ. Gastrointestinal Disorders. (Chapter 171) In: Walls R, et al. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 9th ed., 2018: 2126 -1804.e2
Dähnert W. Radiology review manual. Lippincott Williams & Wilkins. (2003) ISBN:0781738954.