Gallstones are pebble-like nuisances that can form inside the gallbladder. The gallbladder is a pouch that collects bile as that liquid flows from the liver to the intestine through the bile ducts. Bile is a fluid that is made, in part, to help with digestion. The salts in bile make it easier for you to digest fat. Bile also contains some waste products including cholesterol and bilirubin (created when old red blood cells are destroyed). Gallstones form in the gallbladder when cholesterol or bilirubin particles begin to cluster together into a solid lump. The stone grows in size as the bile fluid washes over it, much like a pearl forms inside an oyster.
Most of the time, gallstones do not cause any symptoms or problems. Small gallstones can leave the gallbladder and its draining ducts, then pass out of the body through the intestines. However, gallstones can cause symptoms if they become caught in the narrow outlet of the gallbladder, or in the ducts that drain the gallbladder. After meals, especially meals high in fat, thin muscles in the wall of the gallbladder squeeze to help release bile into the intestines. If the gallbladder squeezes against a gallstone, or if a gallstone blocks the fluid from draining easily, the gallbladder can ache with a strong, steady pain.
More serious problems can develop if a gallstone gets into the drainage-duct system but does not make it all the way through to the intestines. In this case, the stone can cause a blockage with buildup of bile in the gallbladder or liver. Since the digestive tract is contaminated by bacteria, blocked fluid can lead to a very serious infection. If a gallstone lodges low down in the draining ducts, it can also block drainage of digestive enzymes from the pancreas. This can lead to inflammation of the pancreas (pancreatitis).
Gallstones are very common. They occur in 1 out of 5 women by age 60, and they are half as common in men. Gallstones occur more commonly in older people, in people who are overweight, and in people who lose weight suddenly. They also are more likely to occur in women who have been exposed to extra estrogen over their lifetime by having multiple pregnancies, by taking birth control pills, or by taking hormone replacement after menopause.