On the basis of their composition, gallstones can be divided into the following types: cholesterol stones, pigment stones, and mixed stones. An ideal classification system is yet to be defined. Cholesterol stones
Cholesterol stones vary from light yellow to dark green or brown or chalk white and are oval, usually solitary, between 2 and 3 cm long, each often having a tiny, dark, central spot. To be classified as such, they must be at least 80% cholesterol by weight (or 70%, according to the Japanese classification system). Between 35% and 90% of stones are cholesterol stones. Pigment stones
Bilirubin ("pigment", "black pigment") stones are small, dark (often appearing black), and usually numerous. They are composed primarily of bilirubin (insoluble bilirubin pigment polymer) and calcium (calcium phosphate) salts that are found in bile. They contain less than 20% of cholesterol (or 30%, according to the Japanese classification system). Between 2% and 30% of stones are bilirubin stones. Mixed stones
Mixed (brown pigment stones) typically contain 20–80% cholesterol (or 30–70%, according to the Japanese classification system). Other common constituents are calcium carbonate, palmitate phosphate, bilirubin and other bile pigments (calcium bilirubinate, calcium palmitate and calcium stearate). Because of their calcium content, they are often radiographically visible. They typically arise secondary to infection of the biliary tract which results in the release of β-glucuronidase (by injured hepatocytes and bacteria) which hydrolyzes bilirubin glucuronides and increases the amount of unconjugated bilirubin in bile.
Gallstones within the ampulla of Vater can obstruct the exocrine system of the pancreas and can result in pancreatitis. Signs and symptoms
Gallstones, regardless of size or number, are often asymptomatic. These "silent stones" do not require treatment and can remain asymptomatic even years after they form.A characteristic symptom of a gallstone attack is the presence of colic-like pain in the upper-right side of the abdomen, often accompanied by nausea and vomiting. Pain from symptomatic gallstones may range from mild to severe and can steadily increase over a period lasting from 30 minutes to several hours. Other symptoms may include fever, as well as referred pain between the shoulder blades or below the right shoulder. If one or more gallstones block the bile ducts and cause bilirubin to leak into the bloodstream and surrounding tissue, jaundice and itching may also occur. In this case, liver enzyme levels are likely to be raised.Often, gallbladder attacks occur after eating a heavy meal. Attacks are most common in the evening or at night. Other complications
In rare cases, gallstones that cause severe inflammation can erode through the gallbladder into adherent bowel, potentially causing an obstruction termed gallstone ileus.Other complications can include ascending cholangitis, which occurs when a bacterial infection causes purulent inflammation in the biliary tree and liver, and acute pancreatitis caused by blockage of the bile ducts that prevents active enzymes from being secreted into the bowel, instead damaging the pancreas. Rarely, gallbladder cancer may occur as a complication.