Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Seek emergency medical care immediately if a baby or child has:
Dark or bright green vomit
Sudden, severe, or worsening abdominal pain
A swollen, hard, or very tender abdomen
Blood in vomit or stool
Unusual sleepiness, limpness, confusion, or difficulty waking
Pale, cold, mottled, or bluish skin
Breathing difficulty, collapse, or signs of shock
Repeated vomiting with an inability to keep fluids down
Do not give food or drink unless the emergency team advises it, because anaesthesia and surgery may be needed.
If vomit becomes green or the child becomes acutely unwell, seek emergency care instead.
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Do not wait for a routine appointment when volvulus is possible.
For less urgent concerns, arrange routine medical review for repeated abdominal pain, feeding difficulty, poor growth, persistent changes in bowel habits, or vomiting that keeps returning.
Every sign above is quoted from the sofidex article on Volvulus - childhood. If you are not sure, err upward — it is always reasonable to be checked.