What is the diagnosis for a 15-day-old male presenting with bilious vomiting and abdominal distension, and a gasless abdomen on X-ray?

The clinical presentation of a 15-day-old male with bilious vomiting, abdominal distension, and a gasless abdomen on X-ray strongly indicates a diagnosis of midgut malrotation.

In midgut malrotation, the mesenteric attachments of the small intestine are abnormal, which can lead to obstruction. The lack of gas in the abdomen suggests that there is a blockade preventing gas from passing through the intestines, which aligns with the symptoms of bilious vomiting and abdominal distension. Bilious vomiting occurs because the obstructed intestines are unable to process and pass the included bile backward, indicating that the obstruction is distal to the duodenum where bile enters the intestinal lumen.

Identifying midgut malrotation is crucial because it can lead to serious complications, such as volvulus, where the intestines twist around themselves and can compromise blood supply, leading to necrosis.

The other conditions listed may present with similar symptoms but differ significantly in their clinical presentation or age of onset. Pyloric stenosis typically presents with projectile non-bilious vomiting in infants usually aged 3-12 weeks, intestinal atresia often presents with bilious vomiting very early after birth, and meconium ileus typically occurs in newborns with cyst