Gallstones are small hard accumulations of substances within the gallbladder or in the bile duct system. The two most common classifications of gallstones are cholesterol gallstones and pigment gallstones, reports National Digestive Diseases Information Clearinghouse. Pigment stones are usually small, and black or brown. The stones can range in size from extremely tiny to as large as a golf ball. Understanding what causes pigment stones can help in the prevention and diagnosis of the condition. Treating the underlying cause typically reduces the risk of developing pigment gallstones.
Hemolytic anemia is a condition characterized by a deficiency of blood cells caused by a destruction of the cells. The cells are either structurally abnormal or deficient in certain nutrients. Hemolytic anemia can be a cause of pigment stones, according to the University of Maryland Medical Center. Pigment stones caused by hemolytic anemia are typically black. As the red blood cells are destroyed, they release a dark reddish brown pigment called bilirubin. This pigment is what gives the gallstones their color.
Escherichia Coli Infection
Escherichia coli, or E. coli, infection can cause pigment stones, states the "Annals of Surgery" in the article “Pathogenesis of calcium bilirubinate gallstone.” E. coli is a bacteria that is found within the colon and stool of the digestive system. Patients are infected with the bacteria when they accidentally ingest contaminated food or water products. E. coli usually causes food poisoning, but research shows that many patients with pigment stones have large concentrations of the bacteria within their bile. Eliminating the infection can reduce the risk of pigment gallstones.
Sickle Cell Anemia
Sickle cell anemia can be a cause of pigment gallstones, according to the National Digestive Diseases Information Clearinghouse. Sickle cell disease is a genetic disease that causes deformation of red blood cells. The cells become shaped like a crescent or sickle. These deformed cells are easily broken as they travel through the vessels and organs of the body. As the cells are destroyed, they release large amounts of bilirubin, which accumulates in the gallbladder. This accumulation leads to the development of many pigment stones.
Roundworms, such as Ascaris lumbricoides, can contribute to the formation of pigment stones, reports the "Annals of Surgery." Over 70 percent of patients with pigment gallstones have parts of roundworms or their eggs within the stones. These roundworms populate the gallbladder and the bile ducts, often causing a buildup of bile. As the worms die and breakdown, they aid in the formation of pigment stones.
Livers that are chronically being damaged begin to scar. This scarring of the liver is called cirrhosis, and causes the liver to function abnormally. Cirrhosis is a cause of pigment stones, according to the National Digestive Diseases Information Clearinghouse. The cirrhosis causes the liver to produce large amounts of bilirubin, which increases the risk of the formation of pigment gallstones.