My son has a loss of appetite and and extremely rumbling stomach. what could this be?

Rumbling tummy : Loss of appetite and a rumbling stomach in a healthy 3 year old may be caused by a virus infection, or most likely food that he/she just is not tolerating well. Check on any unusual of foods that may have been ingested, if so avoid for several weeks and then re-introduce to see if symptoms can be duplicated. Monitor for any vomiting, diarrhea, fever, pain. Maintain a bland diet for 48 hours.

Loss of appetite: Your child's rumbling stomach and loss of appetite may be a sign on impending diarrhea.