Gallstones are hardened deposits of digestive fluid that form within the gallbladder, a small organ located beneath the liver. The gallbladder stores and concentrates bile, which is produced by the liver to help the body digest fats. When an imbalance occurs in the chemical makeup of this fluid, crystals can form and eventually solidify into stones. These stones can range from the size of a grain of sand to a golf ball.
Gallstones Versus Kidney Stones
The misunderstanding about gallstone passage arises from their similar name to kidney stones, but the two are distinct conditions. Gallstones form in the biliary system, which is part of the digestive tract. The pain typically presents in the upper right or central abdomen, sometimes radiating to the back or shoulder blade.
Kidney stones are crystal formations that develop in the kidneys and are part of the urinary system, which filters waste from the blood to create urine. These stones exit the body through the urinary tract (ureters and urethra), leading to their expulsion in the urine. Gallstones follow the path of the digestive tract and do not enter the urinary system, meaning they cannot be “peed out.”
Composition and Formation
The chemical composition of gallstones dictates their behavior and formation. The majority of gallstones (about 80%) are known as cholesterol stones, which appear yellowish in color. These stones form when bile contains an excessive amount of cholesterol that bile salts cannot fully dissolve, causing the excess to crystallize and harden.
The less common type are pigment stones, which are dark brown or black and form when bile contains too much bilirubin. Bilirubin is a yellow pigment produced when the body breaks down old red blood cells, and its excess can be related to conditions like liver cirrhosis or certain blood disorders. Both types can also form if the gallbladder does not contract or empty frequently enough, allowing the bile to become overly concentrated.
The Natural Passage Route
If a gallstone is small enough to move out of the gallbladder, it follows the anatomical route of the biliary tree and the digestive system. The stone first travels from the gallbladder into the cystic duct. From there, it moves into the common bile duct, which carries bile from the liver and gallbladder down to the small intestine.
The stone’s movement through this narrow duct can cause sudden, intense pain known as biliary colic, which occurs when the stone temporarily blocks the flow of bile. If the stone successfully navigates this pathway, it passes through the major duodenal papilla and enters the small intestine. Once in the intestine, the gallstone is eliminated from the body in the stool.
When Medical Intervention is Necessary
While a small gallstone may pass on its own, most symptomatic gallstones require medical intervention because they are too large or become lodged and cause complications. A common complication occurs when a stone blocks the cystic duct, leading to inflammation of the gallbladder called cholecystitis. Blockage of the common bile duct or the pancreatic duct can lead to serious issues like jaundice or pancreatitis.
The definitive treatment for symptomatic gallstones is surgical removal of the entire gallbladder, a procedure called cholecystectomy. This is most often performed using a minimally invasive laparoscopic technique, which involves several small incisions and a camera. For stones stuck in the common bile duct, an endoscopic procedure called Endoscopic Retrograde Cholangiopancreatography (ERCP) can be used to locate and remove them. Non-surgical options, such as oral dissolution medications, are rarely used and are reserved for select patients with small, non-calcified cholesterol stones who cannot undergo surgery, as the treatment can take months or years to be effective.