Cholesterol stones are usually white or yellow in color and account for about 80 percent of gallstones. They are made primarily of cholesterol.
Pigment stones are small, dark stones made of bilirubin and calcium salts that are found in bile. They account for the other 20 percent of gallstones. Risk factors for pigment stones include cirrhosis, biliary tract infections, and hereditary blood cell disorders, such as sickle cell anemia. Stones of mixed origin also occur.
Gallstones can occur anywhere within the biliary tree, including the gallbladder and the common bile duct. Obstruction of the common bile duct is choledocholithiasis; obstruction of the biliary tree can cause jaundice; obstruction of the outlet of the pancreatic exocrine system can cause pancreatitis. Cholelithiasis is the presence of stones in the gallbladder - chole- means "gall bladder", lithia meaning "stone", and -sis means "process".
Gallstones vary in size and may be as small as a grain of sand or as large as a golf ball. The gallbladder may develop a single, often large, stone or many smaller ones, even several thousand.
What causes gallstones?
Progress has been made in understanding the process of gallstone formation. Researchers believe that gallstones may be caused by a combination of factors, including inherited body chemistry, body weight, gallbladder motility (movement), and perhaps diet.
Cholesterol gallstones develop when bile contains too much cholesterol and not enough bile salts. Besides a high concentration of cholesterol, two other factors seem to be important in causing gallstones. The first is how often and how well the gallbladder contracts; incomplete and infrequent emptying of the gallbladder may cause the bile to become overconcentrated and contribute to gallstone formation. The second factor is the presence of proteins in the liver and bile that either promote or inhibit cholesterol crystallization into gallstones.
Other factors also seem to play a role in causing gallstones but how is not clear. Obesity has been shown to be a major risk factor for gallstones. A large clinical study showed that being even moderately overweight increases one's risk for developing gallstones. This is probably true because obesity tends to cause excess cholesterol in bile, low bile salts, and decreased gallbladder emptying. Very low calorie, rapid weight-loss diets, and prolonged fasting, seem to also cause gallstone formation.
In addition, increased levels of the hormone estrogen as a result of pregnancy, hormone therapy, or the use of birth control pills, may increase cholesterol levels in bile and also decrease gallbladder movement, resulting in gallstone formation.
No clear relationship has been proven between diet and gallstone formation. However, low-fiber, high-cholesterol diets, and diets high in starchy foods have been suggested as contributing to gallstone formation.
Cholesterol gallstones can be sometimes be dissolved by oral ursodeoxycholic acid. Treatment of the obstruction of the common bile duct can sometimes be achieved by endoscopic retrograde sphinceterotomy (ERS) following endoscopic retrograde cholangiopancreatography (ERCP).
Cholecystectomy (gallbladder removal) has a 99% chance of eliminating the recurrence of cholelithiasis. There are two surgery options: open procedure and laparoscopic: see the cholecystectomy article for more details.
Open procedure: This involves a large incision into the abdomen (laparotomy) below the right lower ribs. A week of hospitalization, normal diet a week after release and normal activity a month after release.
Laparoscopic: 3-4 small puncture holes for camera and instruments (available since the 1980s). Typically same-day release or one night hospital stay, followed by a week of home rest and pain medication. Can resume normal diet and light activity a week after release. (Decreased energy level and minor residual pain for a month or two.)