“If the child is complaining about stomach pain, but is still playing, laughing and eating, chances are it’s nothing serious,” says Dr. Michelle Goldberg, a physician on the medical staff at Children’s Medical Center of Dallas. “If the child is complaining about very severe pain and is not doing these things as he or she normally does, have the child seen by a doctor right away.”

Here are three good reasons to take a troubled tummy to the doctor at once:

1. Severe pain that starts near the navel and spreads to the lower right part of the belly. This can mean appendicitis.
2. Belly pain with blood in either the vomit or stool.
3. Green liquid vomit. This could be bile, a sign of torsion — a twisting of intestines that must be treated quickly.

One common problem, gastroenteritis, looks like an emergency but usually isn’t. Usually caused by a virus, it strikes fast and hard with abdominal pain, vomiting and diarrhea. Most cases ease up quickly. But if it doesn’t — or if your child exhibits dehydration, a bloated abdomen or an altered mental state — see the doctor.

“Dehydration is serious, and requires treatment,” Dr. Goldberg adds. “Watch out for decreased fluid intake, decreased urine output and a decrease in the production of tears.”

For many children, however, stomach pain is a result of constipation. Common causes of constipation are an inadequate intake of fluids and diets high in fats. Simple dietary fixes often can correct the problem. Infrequent constipation is normal; however, constipation that lasts longer than three weeks should be referred to a pediatrician.