My 5-year-old was complaining of stomach pain, and I was worried and had questions. I asked her how bad the pain was and where it hurt and whether it was getting worse. Being a kindergartner, she couldn't answer my anxious questions with much clarity.

I was worried about appendicitis. Maybe I'd been conditioned by my early devotion to the children's book Madeline and her sudden, urgent crisis in the middle of the night. Isn't appendicitis what all parents worry about when a child complains of stomach pain?

I called my pediatrician's office and got an after-hours call back. The doctor quickly guessed what was making me fret.

"If you want to check for appendicitis, you can do the jump test," she said.

"The what?"

"Just get her to jump and see if she doubles up in pain," she said. "If not, you don't need to worry so much — it's probably just something she ate or constipation."

I got off the phone and duly got my 5-year-old to jump. She wasn't happy about it, but it clearly didn't cause her a huge amount of pain. My stress level plummeted. I took a deep breath and went back to offering apple juice and saltines and riding it out.

The jump test is a real thing, Jennifer Shu, a pediatrician in Atlanta, assures me. "There are studies on the jump test," she explains. "They look at what are the chances if you have a positive jump sign that you also have appendicitis, and it's around 70% — so it's high, but it's not a perfect test."

The appendix is a small, dead-end tube that branches off the large intestine on the lower-right side of your abdomen. When it gets inflamed, it causes severe pain and needs to be surgically removed at a hospital quickly, before it ruptures.

The beauty of the jump test is that it's so simple and you don't need any special training to do it, Shu says. When you have inflammation or an infection anywhere in your abdomen, the lining of the abdominal cavity, called the peritoneum, can get inflamed, she explains. "That's called peritonitis, and some of the signs of peritonitis are not being able to walk or jump."

With the jump test, "the whole premise is that if you jostle that inflamed peritoneum, is there going to be pain?" she says. "And one way to check it is — if a child jumps, if there's pain, that's probably a sign that the peritoneum is inflamed."

There are a few other home tests you can try along with the jump test, Shu says. "If you're lying down and you press on the left-lower quadrant, is there pain in the right-lower quadrant?" she says. If there is, that's another sign of peritonitis and possibly appendicitis.

Another test: "If you press down over the appendix on the right-lower quadrant, is there more pain when you let up? That's called rebound." Rebound pain is another sign of possible trouble.

Shu also has tips for doing these tests with your kid. First, try to get the child distracted by putting on a video or something like that. Next, "start pushing on a place where you know it doesn't hurt — their arms, push on their chest, push on their legs — and then kind of move your way to the parts of the belly where the appendix is," she explains. "If they kind of flinch, then you kind of go away from it, go back to it, and if it's kind of reproducible and consistent, then you think, 'Oh, I'm a little bit worried.'"

She says typically the pain starts in the middle of the abdomen and then migrates to the lower right.

Shu also advises observing the whole child. Do they have a fever? Are they vomiting and have no appetite? Are they listless? Are they grimacing from pain?

If your reasons to be worried are adding up rather than diminishing, get your child into the pediatrician as soon as you can, or just head to the hospital.

Hospital staff may use blood tests and imaging, like an ultrasound or CT scan, to diagnose appendicitis. And if your child does have it, know that medicine has come a long way since Madeline, whose classmates loved seeing her scar.

"Many of my patients have laparoscopic surgery where they just go through the bellybutton and there's not really a big scar," Shu adds.

If you, like me, have a tendency to imagine the worst-case scenario when your kid is sick, it's helpful to know some basic statistics. Appendicitis is not super-common among preschool-age kids, explains Shu.

"I have about 5,000 patient visits a year — I had one child this year who had appendicitis," she says. "That's pretty typical."

That tracks with national estimates that 1 to 2 young children per 10,000 have acute appendicitis each year, although the incidence rises to 25 per 10,000 for kids ages 10 to 17.

"The most common causes of stomach pain would be things like constipation, a stomach virus, anxiety, eating some weird food," Shu notes.

Most likely, it's one of those things. If you're worried, just see what happens when they jump.