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What Is the Gallbladder?

The gallbladder is a four-inch, olive-shaped muscular sac that lies under the liver in the right side of the abdomen. It acts as a reservoir for bile, a fluid made in the liver. Bile is important for the digestion of fat and also carries some waste products out of the body. The gallbladder is connected to the liver and small intestine through a system of small channels called ducts. When food enters the small intestine, a hormone called cholecystokinin is released, signaling the gallbladder to contract and release bile. The bile flows through the common bile duct into the small intestine. Bile breaks down (emulsifies) fat so that it can be absorbed along with fat-soluble nutrients such as vitamins A, D, E, and K into the bloodstream. Bile is composed of water, bile salts, lecithin (a fat known as a phospholipid), and cholesterol.

Gallstones can develop

Gallstones are small, hard pellets that form in the gallbladder when the concentration of cholesterol or bilirubin in the bile becomes higher than normal, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Gallstones can vary in size from a few millimeters to several centimeters in diameter. Usually, gallstones occur as people get older. They are more common in women than in men. Other risk factors for gallstones include diabetes, being overweight, weight cycling (losing then regaining weight), Crohn's disease, and cirrhosis of the liver.    

Most gallstones are made of cholesterol. Others are made of calcium bilirubinate, or calcified bilirubin. Bilirubin is formed from the breakdown of hemoglobin, the red oxygen-carrying component in red blood cells, and is normally excreted in bile.

Gallstones can remain in the gallbladder or pass into the ducts that carry bile to the small intestine. Most people with gallstones don't even know they have them. But in some cases, a stone may cause the gallbladder to become inflamed, a condition called cholecystitis. This can cause pain and—possibly—infection, the NIDDK says.

When symptoms occur

Gallstones that remain in the gallbladder generally cause no symptoms, or only vague symptoms such as gas, nausea, and abdominal discomfort after meals. If a gallstone becomes lodged in the system of ducts that carry bile to the small intestine, a condition called choledocholithiasis, it may cause symptoms that include:

  • Severe, cramping pain in the upper right abdomen

  • Fever and chills

  • Nausea and vomiting

  • Yellowing skin (jaundice)

If the pain lasts for hours, the gallbladder can become inflamed. A serious complication of acute, untreated inflammation is infection that can cause an abscess, gangrene, or septicemia—an infection that spreads to other parts of the body.

A gallstone can also block the duct from the pancreas that joins the common bile duct. If this occurs, it can cause pancreatitis, inflammation of the pancreas, which can also be life-threatening.

Gallstones can be treated by medicine that will slowly dissolve the stones, by sound waves that break up stones, and by surgery that removes the gallbladder, the NIDDK says.