Picture trying to squeeze a golf ball through a straw. Those suffering from gallstones need not imagine it; they may experience it firsthand.

Certainly, not all gallstones are the size of a golf ball. They can be as small as a pea or a grain of sand. But whatever the girth, the result is the same: pain.

"Gallstone pain, or biliary colic, is believed to be due to a temporary blocking of the cystic duct or the common bile duct. This leads to increased pressure and distension, which causes the pain," says gastroenterologist Shelly Lu, M.D., professor of medicine at the Keck School of Medicine of USC. "Usually the pain is relieved when the stone either falls back into the gallbladder or passes out of the bile duct."

Gallstones form when certain components in bile solidify. Bile, which is created by the liver and is stored in the gallbladder, helps the body digest fats. When bile is needed, the gallbladder contracts and squeezes bile into the common bile duct, a tube that carries it to the small intestine.

Water, proteins, fats, cholesterol, salts and bilirubin all make up the recipe for bile. But if bile contains too much cholesterol, salts or bilirubin, these can precipitate and form stones. Most stones are made mainly of hardened cholesterol.

Although many people believe that eating high-fat or fried foods brings on gallstones, Lu calls that a misconception.

"Because fat is the most potent stimulus for cholecystokinin release - a type of a hormone that stimulates gallbladder contraction - it seems logical that painful attacks might occur more with rigorous gallbladder contraction, but there is no proof that this is true," she says.

High triglyceride levels - but not cholesterol level - are associated with cholesterol stones, Lu says, but no specific diets have been proven to lower the risk. She notes, "However, it is always a good idea to encourage a low-fat diet for overall health."