Abdominal Distension in Neonates: Etiology and Diagnosis

Anatomic Causes by Location

The American Academy of Pediatrics recommends that duodenal atresia be suspected in neonates presenting with bilious vomiting within the first 2 days of life and the classic "double bubble" sign on radiographs, which is caused by failure of recanalization of the primitive gut lumen during embryologic development, and is characterized by absent or abnormal meconium passage at birth 2
The American College of Radiology suggests that contrast enema is the diagnostic procedure of choice for suspected distal obstruction, as it differentiates between functional abnormalities, surgical pathologies, and conditions requiring therapeutic enema, and may show multiple dilated loops and absent or decreased distal gas, with microcolon visualized due to lack of contents moving through the bowel 3, 4

The Society of Critical Care Medicine states that necrotizing enterocolitis (NEC) presents with increased apnea/bradycardia episodes, followed by abdominal distension, bloody stools, and bilious emesis, and has a survival rate close to 95% unless it involves the entire bowel, which occurs in approximately 25% of cases with 40-90% mortality, and the three essential components for NEC include substrate for bacterial growth, infectious agent, and bowel damage from vascular compromise 1
The American Institute of Ultrasound in Medicine recommends that point-of-care ultrasound (POCUS) be used to detect free fluid, bowel wall thickness, pneumatosis intestinalis, portal venous gas, and vascular perfusion in NEC, as it outperforms conventional radiography for detecting pneumatosis intestinalis or portal venous gas 5, 6

The American College of Radiology suggests that plain abdominal radiographs be the first imaging study for all suspected bowel obstruction, as they demonstrate dilated bowel loops, air-fluid levels, and presence or absence of distal gas, and upper GI series remains the reference standard for suspected malrotation/volvulus 3
The Society of Critical Care Medicine recommends that POCUS be used to detect free intra-abdominal fluid, assess bowel peristalsis, and guide peritoneal drainage in critically ill neonates 5, 6