Gallstones are crystallized substances that can occur within the biliary tree, including the gallbladder and the common bile duct. These stones are composed of cholesterol, bile pigments, and calcium salts. The size varies as well as its chemical structure. It can be as small as a sand grain or as large as a golf ball.

Most likely, the gallstone forms in gallbladder as it stores a concentrate of bile. This bile came from the liver that aids digesting food in the intestine, particularly in fat emulsification. The gallstone that forms in gallbladder can block the normal flow of bile when it dislodges into the ducts; the hepatic ducts that carry bile out from the liver. The cystic duct that take bile to and from the gallbladder. And the common bile duct that passes the bile from cystic and hepatic ducts to the small intestine.

Cholesterol gallstones

Cholesterol gallstones are primarily made of cholesterol, which are the most common type of gallstone. The formation of cholesterol gallstone occurs when there is too much cholesterol and less bile salts. Besides too much cholesterol concentration, there are two other processes that cause gallstones. First, the abnormal rapid formation and growth of cholesterol particles, which can be link to the presence of proteins in the liver and bile that either promote or inhibit cholesterol formation into gallstone. Second, the process of irregular contraction and emptying of the gallbladder that store concentrated bile. The incomplete and infrequent emptying allows the bile to stay in the gallbladder longer that contributes to gallstone formation, allowing the cholesterol particles to form and grow.

Pigment gallstones

Pigment gallstones are the second most common type of gallstone. Pigment is a waste product formed from hemoglobin, a principal component of red blood cells. When red cells are broken down due to aging or defects, they produce bilirubin. The bilirubin is then removed from the blood by the liver. When there is more bilirubin in bile, the bilirubin combines with calcium to form pigment. This pigment dissolves poorly in bile and forms particles that grow in size. Much more when the pigment is combined with fats in bile, e.i. cholesterol and fatty acids, it then forms particles that grow into gallstones.

Gallstones can cause several different disorders:
Cholelithiasis is defined as the presence of gallstones within the gallbladder.
Choledocholithiasis is the presence of gallstones within the common bile duct.
Cholecystitis is a disorder marked by inflammation of the gallbladder.
Cholesterolosis or cholesterol polyps is characterized by deposits of cholesterol crystals in the lining of the gallbladder.
Gallstone ileus is a condition in which results from a gallstone’s blocking the entrance to the large intestine.
Cholangitis is a condition in which bile in the common, hepatic, and intrahepatic ducts becomes infected.
Jaundice is a condition in which bilirubin accumulates in the body.
Pancreatitis means the inflammation of the pancreas.
Gangrene of the gallbladder is a condition in which the inflammation of cholecystitis cuts off the supply of blood to the gallbladder.
Sepsis is a condition in which bacteria from any source within the body, including the gallbladder or bile ducts, get into the blood stream and spread throughout the body.
Fistula is an abnormal tract through which fluid can flow between two hollow organs or between an abscess and a hollow organ or skin.
Cancer of the gallbladder.