When a neonate develops bilious vomiting, one should suspect a surgical condition.
[aafp.org]
Patients typically show features of bowel obstruction (abdominal pain, distension, bilious vomiting) or of bowel ischemia and gangrene ( tachycardia, hypotension, hematochezia
[amboss.com]
After the age of 2 months, bilious and non-bilious vomiting occur with equal frequency.
[patient.info]