How Are Gallstones Formed?

Cholesterol Gallstones

Cholesterol gallstones are the most common form of gallstones. Cholesterol gallstones are formed when the liver is unable to produce enough bile acids and lecithin. Cholesterol is often deposited in the liver to help get rid of excess cholesterol from the body. However, since cholesterol is a fat, and bile is a watery solution, the two do not mix well. In order for cholesterol to dissolve in the bile, the liver also secretes lecithin to break the cholesterol down to a form that can be carried through the bile ducts. If not enough lecithin is secreted, the cholesterol is allowed to float to the top and harden into stones. If the patient also has problems with the gallbladder not emptying frequently enough, that can also allow cholesterol gallstones to form.

Pigment Gallstones

Pigment gallstones are the next most frequent type of stone and can come in two varieties, brown and black. Brown pigment gallstone form when there is an obstruction in the bile ducts. This allows bacteria to enter the bile ducts. The bacteria reacts with bilirubin (hemoglobin from destroyed red blood cells) and calcium in the ducts to form pigments. These pigments turn into particles, which clump into stones. Black pigment stones are formed when too much bilirubin is present in the bile ducts, creating the same conditions in which it can combine with calcium or cholesterol to form particles, which then clump to form stones.

Other

There are rare circumstances in which stones can be formed through other means. For example, the antibiotics ceftriaxone can sometimes cause gallstones to form when the medication combines with calcium in the bile to form stones. The stones are usually dissolved once the patient ceases using the antibiotic.

References

• American College of Gastroenterology
• Mayo Clinic
• Gallstones