Bile is made by the liver, stored and concentrated in the gallbladder, and released after meals to help digest fat. Stones form when its components crystallise — most commonly cholesterol stones, though pigment stones occur in conditions where red cells break down excessively, including thalassemia and sickle cell disease.
They are very common, and the majority cause no symptoms at all. Silent stones found incidentally on an ultrasound performed for another reason generally require no treatment, because the chance of them ever causing trouble is modest.
Symptoms appear when a stone temporarily blocks the gallbladder outlet — biliary colic, a severe constant pain in the upper right abdomen, often radiating to the back or right shoulder blade, typically after a fatty meal, lasting from thirty minutes to a few hours.
The complications are what make gallstones important. Persistent blockage causes cholecystitis, an inflamed and infected gallbladder. A stone escaping into the bile duct causes obstructive jaundice, and if that duct becomes infected, cholangitis — a genuine emergency. And a stone lodging near the pancreatic duct causes acute pancreatitis, which is among the most serious complications of all.