Child vomiting yellow liquid, what kind of disease is it?

Patient's question:

Patient Gender: Male
Detailed Condition and Purpose of Consultation:
My youngest son was fine last night,
but when he woke up this morning, he started vomiting. By the morning, he had vomited 5-6 times,
and all of the vomit was yellow liquid. He has never vomited before.
Could you please ask the expert what might be the reason for this, or what is the most likely cause? Is it serious?
Thank you! Looking forward to a prompt reply.
First Follow-up Question: There is abdominal pain.
He went to the hospital, and they prescribed Motilium.

Doctor's answer:

In your case, it may be gastroesophageal reflux gastritis, also known as alkaline reflux gastritis. This refers to a syndrome caused by bile reflux into the stomach, generally characterized by a series of symptoms such as upper abdominal pain, vomiting bile, bloating, and weight loss. It is recommended to use triple therapy to eradicate Helicobacter pylori, while also adding prokinetic drugs for treatment.