U.S. Department of Health and Human Services Public Health Service National Institutes of Health
What Does the Gallbladder Do?
The gallbladder is a small pear-shaped sac located beneath the liver on the right side of the abdomen. The gallbladder's primary function is to store and secrete bile into the intestine at the proper time to aid in digestion.
What Are Gallstones?
Gallstones are clumps of solid material that form in the bile stored in the gallbladder. There are two major types of gallstones - cholesterol stones and pigment stones.
Cholesterol stones are composed primarily of cholesterol, and they account for about 80 percent of gallstones in the United States.
Pigment stones, which account for other 20 percent of gallstones are composed of bile pigments such as bilirubin, and other substances such as calcium, which are found in the bile.
Gallstones can vary in size. They can be as small as a grain of sand or as big as an egg. The gallbladder may develop a single, often large, stone or many smaller ones, even several thousand.
Small stones can move into the bile ducts and become lodged there, blocking the flow of bile and causing pain and jaundice. Larger stones can block the outlet from the gallbladder and cause steady, sharp pain when the gallbladder tries to empty.
What Causes Gallstones?
Gallstones form when certain chemicals in the bile, either cholesterol or bile pigments, start to clump together. These clumps become the cores from which larger stones can grow. If more cholesterol or bile pigments are deposited, these masses can grow even more and, like a snowball rolling down a hill, can eventually become quite large.
Although researchers do not understand why some people get gallstones and others do not, progress is being made in understanding the process of stone formation.
Scientists have found that certain proteins present in bile saturated with cholesterol or bile pigments may play a role in either causing or preventing gallstones. One of these proteins seems to promote the formation of stones, while a second protein is thought to inhibit stone formation.
Researchers currently believe that an imbalance of these two proteins may cause gallstones. That is, stones may be more likely to form in people who have too much of the promoting factor or too little of the inhibiting factor. The gallbladder itself also may contribute to the problem by incomplete or infrequent emptying of bile.
Who Gets Gallstones?
This year over 1 million people in the United States will find out that they have gallstones. They will join the estimated 20 million Americans - roughly 10 percent of the population - who already have gallstones.
Although anyone may be a potential candidate for gallstones, the condition occurs more often in women than in men. In fact, among people between the ages of 20 and 60, women are three times more likely to develop gallstones than are men. However, by age 60 the statistics even out, and nearly 30 percent of all men and women have gallstones. The people most likely to develop gallstones are:
The highest incidence of gallstones in the United States occurs in people of Mexican-American and Native American descent. For example, in some American Indian tribes such as the Pima Indians of Arizona, 70 percent of women have gallstones by age 30. A majority of Native American men have gallstones by the time they reach 60.
American blacks of both sexes have the lowest incidence of gallstones; both male and female whites have a rate twice that of blacks.
What Are the Symptoms of Gallstones?
Most people who have gallstones don't know it. They have what are called "silent" stones. Silent stones are usually detected when a person is undergoing a routine medical checkup or is being examined for some other suspected illness.
Although most people with silent stones may live their entire lives without ever having a gallstone attack, it is impossible to determine who will and who will not have an attack. One of the most difficult questions for people with silent stones is deciding whether (1) to have the gallbladder removed to prevent possible attacks, which may never occur, or (2) to leave the gallbladder intact until an attack does occur, which may happen in later life when the patient could be at a much higher risk for surgery. Such a decision is best made under the guidance of a physician or specialist familiar with the particular patient's case and past medical history.
A gallstone attack usually is marked by a steady, severe pain in the upper abdomen. Such attacks may last only 20 or 30 minutes, but more often they last for several hours. A gallstone attack also may cause pain between the shoulder blades or in the right shoulder and may cause nausea or vomiting. Typically, attacks may be separated by weeks, months, or years. Once a true attack occurs, subsequent attacks are much more likely.
Sometimes, gallstones can make their way out of the gallbladder and into the cystic duct, which is the channel through which bile travels on its way to the small intestine. If stones get lodged in the cystic duct, they block the flow of bile, which may lead to a condition called cholecystitis, an inflammation of the gallbladder. Blockage of the cystic duct is a relatively common complication caused by gallstones.
A less common yet equally serious problem can occur if gallstones lodge themselves in the common bile duct, which can block bile flow not only from the gallbladder but also from the liver. Stones also may interfere with the flow of digestive fluids secreted by the pancreas into the small intestine and lead to pancreatitis, an inflammation of the pancreas.
Prolonged blockage of any of these ducts can cause severe damage to the gallbladder, liver, or pancreas, which can be fatal.
How Are Gallstones Diagnosed?
There are several diagnostic tests available to detect stones.
How Are Gallstones Treated?
Surgery is by far the most common method for treating gallstones. Each year, over 500,000 Americans have their gallbladders surgically removed.
A routine gallbladder operation usually lasts 1 to 2 hours and is performed under a general anesthetic. After the organ is removed the surgeon checks the bile ducts for any stones that may have passed into these channels. However, it is possible for even the best surgeon to miss some stones hidden in the bile ducts. In fact, as many as 10 percent of patients coming out of surgery have stones remaining in the bile ducts.
In some patients, after the gallbladder is removed a T-shaped tube is placed through the abdominal wall connecting the bile ducts to the outside of the body. This tube is left in place for a few days following surgery to enable the surgeon to remove any residual stones without additional surgery.
Although there is always some risk involved in any type of operation, gallbladder surgery is a routine procedure that is relatively risk free when performed by an experienced surgeon in an otherwise healthy individual who has no other complications.
In most people, removal of the gallbladder does not seem to affect the digestion process. Once the gallbladder has been removed, bile produced by the liver flows directly into the small intestine.
However, not all people with gallstones are good candidates for surgery, either because they may be too weak to withstand an operation or because they may have another medical condition that greatly increases the risks involved in surgery. For these patients, other treatments to remove gallstones without surgery may be helpful.
What Are the Alternatives to Gallbladder Surgery?
There are a variety of other methods for treating gallstones, although some are still experimental and are not yet widely available.
The Division of Digestive Diseases and Nutrition
The Division of Digestive Diseases and Nutrition of the National Institute of Diabetes and Digestive Diseases (NIDDK) supports a large amount of research into the causes, treatments, and prevention of gallstones. Through NIDDK support, the results of many basic and clinical research studies are beginning to give scientists a better understanding of why gallstones form. This new knowledge someday may lead to methods for preventing gallstones in those people most likely to develop stones.
In addition, NIDDK-supported researchers are working to develop safer and more cost-effective methods for removing gallstones, which may improve the quality of life for all those afflicted with this disorder.
The Division and the Institute support the National Digestive Diseases Information Clearinghouse (NDDIC), which produces fact sheets and bibliographic information for health professionals and patients. Information on digestive diseases is available from the NDDIC, c/o DD/NIDDK, Building 31, Room 9A04, 9000 Rockville Pike, Bethesda, MD 20892.
Written by Bill Hall Office of Health Research Reports National Institute of Diabetes and Digestive and Kidney Diseases
NIH Publication No. 87-2897
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