Necrotising enterocolitis and point of care neonatal abdominal USS

Abstract

Neonatal intensive care has seen dramatic improvements over last four decades in rates of survival for most preterm newborns. Limits of survival were generally regarded 27 weeks gestation in the 80’s, are now 23 weeks gestation. These micro-premies are much smaller (500 to 800 grams birth weight) and are now increasingly managed with nasal continuous positive airway pressure as respiratory support. Acute abdominal emergencies are common in these infants and can be difficult to distinguish from dysmotile intestinal function in early stages. Preterm infants treated with nasal continuous positive airway pressure often have distended abdomens with feed intolerance requiring evaluation for potentially life-threatening conditions such as necrotising enterocolitis. Plain abdominal radiography is the gold standard modality for diagnosis, monitoring and guiding management in clinically suspected diseased neonatal bowel states. Timely access of expert surgical opinion poses frequent dilemmas of transporting a critically ill preterm infant to a surgical facility. There is compelling evidence demonstrating diagnostic bowel ultrasound findings in necrotising enterocolitis by trained medical ultrasonographers. There is a growing interest in utility of performing bowel ultrasound amongst point-of-care neonatal clinicians. Despite technical challenges, point-of-care bowel ultrasound has the added ability to measure bowel wall thickness, provide real-time evaluation of bowel peristalsis, perfusion, detection of free abdominal fluid; in addition to detection of pneumatosis intestinalis, portal venous gas and pneumoperitoneum like plain abdominal radiographs. This provides a more complete understanding of bowel state. Specific color doppler bowel wall arterial flow patterns have been described in necrotising enterocolitis, as “zebra”, “Y” and the “ring” patterns corresponding to inflamed viable bowel. Bowel ultrasound is more sensitive than abdominal radiography in the detection of pneumotosis intestinalis in early stages of necrotising enterocolitis. As the disease progresses, the visualization of thinned bowel wall with lack of bowel wall perfusion on ultrasound implies nonviable bowel with impending perforation. Detection of this bowel state early is valuable in the clinical management as pneumoperitoneum suggesting bowel perforation on plain abdominal radiograph is a late sign. Rarer diagnoses with acute neonatal surgical conditions can also be assessed with the use of bowel ultrasound such as malrotation. With widening of knowledge and appropriate training in ultrasound techniques, neonatologists will be able to enhance their diagnostic acumen by performing point-of-care bowel ultrasound in addition to plain radiography for a broad array of diseased bowel states in neonates.