Gallstones

Gallbladder Gallstones Diet, Pain, Causes, Symptoms, Treatment

What causes gallstones? (Part 3)

Pigment gallstones

Pigment gallstones are the second most common type of gallstone. Although pigment gallstones comprise only 15% of gallstones in individuals from Europe and the Americas, they are more common than cholesterol gallstones in Southeast Asia. There are two types of pigment gallstones 1) black pigment gallstones, and 2) brown pigment gallstones.

Pigment is a waste product formed from hemoglobin, the oxygen-carrying chemical in red blood cells. The hemoglobin from old red blood cells that are being destroyed is changed into a chemical called bilirubin and released into the blood. Bilirubin is removed from the blood by the liver. The liver modifies the bilirubin and secretes the modified bilirubin into bile.

Black pigment gallstones: If there is too much bilirubin in bile, the bilirubin combines with other constituents in bile, for example, calcium, to form pigment (so-called because it is dark brown in color). Pigment dissolves poorly in bile and, like cholesterol, it sticks together and forms particles that grow in size and eventually become gallstones. The pigment gallstones that form in this manner are called black pigment gallstones because they are black and hard.

Brown pigment gallstones: If there is reduced contraction of the gallbladder or obstruction to the flow of bile through the ducts, bacteria may ascend from the duodenum into the bile ducts and gallbladder. The bacteria alter the bilirubin in the ducts and gallbladder, and the altered bilirubin then combines with calcium to form pigment. The pigment then combines with fats in bile (cholesterol and fatty acids from lecithin) to form particles that grow into gallstones. This type of gallstone is called a brown pigment gallstone because it is more brown than black. It also is softer than black pigment gallstones.

Other types of gallstones. Other types of gallstones are rare. Perhaps the most interesting type is the gallstone that forms in patients taking the antibiotic, ceftriaxone (Rocephin). Ceftriaxone is unusual in that it is eliminated from the body in bile in high concentrations. It combines with calcium in bile and becomes insoluble. Like cholesterol and pigment, the insoluble ceftriaxone and calcium form particles that grow into gallstones. Fortunately, most of these gallstones disappear once the antibiotic is discontinued; however, they still may cause problems until they disappear. Another rare type of gallstone is formed from calcium carbonate.

Reviewed on 4/11/2014
Gallstones Related Articles