Gallstones

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.

The gallbladder is connected to the liver and the small intestine by a series of ducts that transport bile. Collectively, these ducts are called the biliary system. Bile is a yellowish fluid produced by the liver and is made up of soap-like chemicals that keep the cholesterol in the gallbladder in liquid form. The liver can produce as much as three cups of bile in 1 day, and at any one time, the gallbladder can store up to a cup of bile. Cholesterol stones...account for about 80 percent of gallstones in the United States. As food passes from the stomach into the small intestine, the gallbladder contracts and sends its stored bile into the intestine through the common bile duct. Once in the intestine, bile helps to digest and absorb the fats from food that has been broken down by enzymes secreted from the pancreas and the intestine.

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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:

• Women who have been pregnant or who have used oral contraceptives or menopausal estrogen therapy;

• both men and women who are overweight;

• people over 60 years old; and

• people who go on "crash" diets or who lose a lot of weight quickly.

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.

• X-RAYS. There are three different tests that use X-rays to examine the gallbladder or biliary system.

  Oral Cholecystography. This test is used to detect stones in the gallbladder. The procedure requires a patient to swallow pills containing a dye the night before X-rays are taken. This dye is absorbed into the bile and outlines on X-ray film the gallbladder and any stones that may be present.

  PTC (Percutaneous Transhepatic Cholangiography). In this test dye is injected through a very thin tube, called a catheter, that pierces the skin and the wall of the abdomen and is guided through the liver into the bile duct system. The injected dye outlines the network of bile ducts when an X-ray picture of the abdomen is taken and thus can detect stones lodged in the bile ducts.

  ERCP (Endoscopic Retrograde Cholangiopancreatography). This test involves the use of an endoscope, which is a long, flexible tube through which a doctor can directly view the digestive tract. The instrument is passed through a patient's mouth and throat down the esophagus and through the stomach to the site in the small intestine where the common bile duct empties. A smaller tube within the endoscope is used to inject dye directly into the common bile duct, creating a sharp image on X-ray film. Like the PTC test, this procedure also can detect stones that may be blocking the bile ducts.

• ULTRASOUND. An ultrasound examination, also known as ultrasonography, uses sound waves to detect gallstones in the gallbladder. Based on the same technology used to develop sonar during World War II, ultrasonography can create images of internal organs from sound waves that pass through the body.

  To detect gallstones, pulses of sound waves are sent into the abdomen to create an image of the gallbladder. If stones are present, the sound waves will bounce off the stones, revealing their location.

  Although ultrasonography usually is more expensive than other diagnostic tests, it has several advantages. It is a noninvasive technique, which means nothing is injected into or penetrates the body. In addition, ultrasound is painless, it has no known side effects, and it avoids exposure to radiation.

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.

• Endoscopic Papillotomy. In this procedure, an endoscope is passed down the throat and through the stomach into the small intestine to the opening where the bile duct empties into the small intestine. The endoscope is used to widen this opening to allow stones in the bile duct to move more easily into the intestinal tract where they can be passed painlessly out of the body. Sometimes, a wire basket or snare attached to the end of the endoscope is used to actually grab lodged stones and pull them through the opening valve into the intestine. This procedure is useful only for removing stones lodged in the bile ducts. It cannot be used to remove stones from the gallbladder.
• Monooctanoin (Moctanin). Monooctanoin is a chemical solvent that was approved in November 1985 by the U.S. Food and Drug Administration for dissolving stones lodged in the bile duct. The drug is injected directly into the bile duct either through an endoscope guided from the mouth, through the digestive tract and into the duct, or through a T-tube left in place after surgery. Small amounts of the chemical are flushed continuously into the bile duct to slowly dissolve the stones. This procedure is effective only in dissolving cholesterol gallstones located in the bile ducts.
• Chenodiol (Chenix). Chenodiol is a prescription drug that can dissolve cholesterol gallstones in some people. Chenodiol is actually an acid normally found in bile that plays a role in keeping biliary cholesterol in solution. Chenodiol tablets work by decreasing the levels of cholesterol secreted in the bile. This action allows the normal cholesterol-dissolving mechanisms in bile to concentrate on redissolving the cholesterol gallstones. The drug is recommended primarily for those people who are not healthy enough to undergo surgery, because treatment can take 2 years or longer and cause side effects including diarrhea and reversible elevation of liver enzymes in the blood. Chenodiol works only on cholesterol gallstones, and its effectiveness depends on the size and number of stones a person has. In fact, even in patients whose stones dissolve completely, 25 to 50 percent of those people may have gallstones recur within 5 to 10 years after chenodiol treatment has ended.
• Methyl Tert-butyl Ether (MTBE). MTBE is a chemical that currently is being tested as another means to dissolve gallstones. MTBE is a common laboratory dissolving solution closely related to diethyl ether, a commonly used anesthetic. In this experimental procedure, a tiny catheter is inserted into the abdomen through the skin and guided through the liver, directly into the gallbladder. Then, small amounts of MTBE are continuously flushed in and out of the gallbladder through the catheter. In tests so far, stones have begun to dissolve within a few hours and have completely disappeared within 1 to 3 days. In patients tested so far, very few side effects have occurred. Occasionally, some MTBE may escape into the intestine and cause nausea. MTBE treatment is still experimental and full-scale tests still need to be done to see if the chemical causes any other side effects and how often stones recur. However, if MTBE therapy proves to be successful, it may provide a safe and cost-effective means of treating gallstones without surgery.
• Ursodiol (Actigall). Ursodiol is a newly-available drug that dissolves cholesterol gallstones when taken orally and has been found to be a safe and effective alternative to gallbladder surgery for some patients. Ursodiol is a bile acid that lowers the amount of cholesterol in the bile and slowly dissolves gallstones within 6 to 24 months, depending on the size of the stones. The action of ursodiol is similar to that of chenodiol, already described.

  Many people who have cholesterol gallstones, with no obstruction of bile flow to and from the gallbladder, may be candidates for treatment with ursodiol. The treatment may be of particular interest for patients who are at high risk for surgery. The drug has been tested in Europe, Asia, and the United States, and has been found to be well tolerated by patients, with only rare instances of mild, transient diarrhea reported.

• Shock Wave Therapy. Extracorporeal shock wave lithotripsy (ESWL) was developed in West Germany as a method of shattering kidney stones instead of removing them through surgery. Currently, ESWL is being used to disintegrate gallstones at certain medical centers throughout the United States. ESWL is generally performed in conjunction with ursodiol/chenodiol treatment.

  During ESWL therapy, high energy shock waves are created and sent through water and into the patient's body. When the shock waves hit the stones, the stones shatter into small fragments that are then more easily dissolved by ursodiol and Chenodiol.

  Unlike the kidneys, which are unobstructed by other organs from the back side of the body, the gallbladder lies buried deep within the body. If not done properly, misdirected shock waves may damage lung tissue.

  Another factor complicating the use of shock waves on gallstones involves the shape of the gallbladder. The opening from the gallbladder to the bile duct is near the top of the organ, but gravity tends to make shattered pieces of gallstones settle to the bottom of the gallbladder, preventing the pieces from passing into the bile ducts. In addition, the cystic duct leading from the gallbladder is tiny and shaped like a corkscrew. If not removed, some stone fragments may move into the bile duct and cause blockage. Some scientists suggest the possible use of a combination treatment involving shock waves to shatter gallstones and a solvent such as MTBE to rapidly dissolve the remaining fragments.

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