Nearly everyone has had a stomachache at some point. But really, any organ in your abdomen (there are many) could be to blame.
Gallstones are stones that form in the gallbladder, a tiny sac that hangs out under the liver, disgorging bile as needed to digest fats.

These stones cause swelling and can block the duct into the intestine, resulting in pain. Gallstone pain tends to strike the right side of the upper abdomen, particularly after fatty meals.

Such meals trigger the gallbladder to contract. “If the gallbladder is inflamed, any contraction of that nature will be amplified and typically will cause pain to the patient,”