gallstones - Medical Dictionary

Home | gallstones - Medical Dictionary |


gallstones		Solid crystalline precipitates in the biliary tract, usually formed in the gallbladder.Gallstones, derived from the bile, consist mainly of calcium, cholesterol, or bilirubin. [ Articles \| Books \| Images \| Discussion groups ]

Additional comments : (Biliary Calculi) Understanding gallstones Gallstones affect an estimated 10 to 15 percent of the population, according to the National Institutes of Health. Most gallstones, composed mainly of hardened cholesterol clusters, are smaller than 2 centimeters in diameter--slightly smaller than an inch--and some patients never develop symptoms. But gallstones can cause serious problems, ranging from chronic pain and pancreas damage to blocked ducts requiring surgery and an increased risk of gallbladder cancer, the NIH has reported. How do gallstones form? After a meal, hormones prompt the gallbladder to release bile into the gastrointestinal tract. Produced in the liver and stored downstream in the gallbladder, this yellow-brown fluid breaks down fats, and it helps the body absorb fat-soluble vitamins such as A, D, E and K. Because water can't dissolve cholesterol, it must be delivered to the gastrointestinal tract inside carrier structures--mainly fluid-filled spheres or "vesicles" made from lecithin. A waxy substance found in egg yolks, lecithin "self-assembles," or curls up to form tiny spheres within bile. A second cholesterol carrier within bile is a rod-like cluster of bile salt molecules known as a micelle. Unfortunately, micelles prefer to dissolve lecithin, and tend to dissolve more lecithin than cholesterol. The action of micelles, therefore, results in cholesterol-enriched vesicles, which are prone to nucleation. Various proteins also affect the rate at which cholesterol "nucleates" or leaves the lecithin spheres. Once cholesterol clusters reach a critical size, they are considered to be a nucleus. At that point, the nucleus can only grow larger. It will never again dissolve back to free cholesterol. It will grow and eventually crystallize, sometimes resulting in macroscopic gallstones. Pinpointing growth factors Within the rich, chemical broth of bile, a number of proteins are believed to either promote or slow cholesterol nucleation and, therefore, gallstone growth. Clinicians describe these enzymes as "pro-nucleating" or "anti-nucleating" factors. To identify the key players in gallstone formation, UD researchers developed a system for observing the interactions of cholesterol and lecithin within artificial bile, a complex soup synthesized in Kaler's laboratory. Specifically, they "tagged" the two molecules with a pair of naturally glowing (fluorescent) analogs: dehydroergosterol, a chemical twin for cholesterol; and dansylated lecithin, which resembles the lecithin molecule found in bile. ("Dansyl" is an acronym for DimethylAminoNaphthalene-Sulfonyl.) Whenever these glowing, analog molecules come within 50 nanometers of each other--a distance equivalent to the diameter of a typical lecithin sphere--they undergo a process of energy transfer. Using a spectrometer to detect ultraviolet light, the UD researchers could "see" cholesterol leaving lecithin vesicles, based on changes in the extent of the energy transfer between the two analog molecules. An increase in the dehydroergosterol signal, coupled with a decrease in the dansylated lecithin signal, told the researchers that cholesterol had nucleated. As expected, introducing phopholipase C to the sample dramatically increased nucleation speeds. The enzyme seems to accelerate the process, through a chemical reaction involving calcium, which forms diacylglycerol on the outer layer of the lecithin vesicle. Because diacylglycerol doesn't dissolve in water, resulting vesicles more rapidly form cholesterol-rich clusters. Phospholipase C has long been known to promote gallstone growth, but the new UD technique made it possible to better understand the enzyme's chemical function and behavior. And, the UD technique gave researchers their first glimpse of nucleation events in process. Source: University of Delaware Weight cycling associated with increased risk for gallstones among men Intentionally losing weight and then regaining it may increase men’s risk for gallstones later in life, according to a report in the JAMA/Archives journals. Gallstone disease—which occurs when a solid mass of cholesterol, bile and calcium salts forms in the gall bladder—is common among adults in Western countries, according to background information in the article. Obesity is a risk factor for gallstone disease, as is rapid weight loss for the treatment of severe obesity. "Although approximately 30 percent of adult U.S. men are trying to lose weight, intentional weight loss is rarely sustained and is often associated with unintentional weight regain, leading to weight cycling," the authors write. "The long-term health consequences of repeated intentional weight loss and the mechanisms of weight recovery are still not well understood. Studies have suggested that large weight fluctuations at some point earlier in life represent an independent risk factor for chronic diseases, including metabolic syndrome." "The potential mechanisms contributing to the association between weight cycling and gallstone formation observed in our study are likely to be multiple," the authors write. When an individual loses and then regains weight, much of that additional weight is made up of body fat. "Studies have shown that large swings of body weight, especially the phase of weight recovery, are particularly sensitive to the accumulation of body fat and to the development of metabolic abnormalities, including insulin resistance, and thereby may facilitate gallstone formation," they write. In addition, levels of the compounds leptin and insulin in the blood have been shown to be higher in weight cyclers than weight maintainers, which could also contribute to gallstone risk. Source: JAMA and Archives Journals Lack Of Exercise, High Intakes Of Sugar And Saturated Fat: A Recipe For Gallstones, UB Study Finds The Western lifestyle of little exercise, lots of saturated fat, loads of refined sugar and little fiber is a major risk factor for the development of yet another chronic medical condition -- gallstones -- a new University at Buffalo study shows. Results showed that body mass index and intake of refined sugar and saturated fat were directly associated with the formation of gallstones. The relationship between saturated fat and gallstones was stronger in men than in women. Conversely, physical activity and a diet high in monounsaturated fat and insoluble dietary fiber were protective against gallstones, results showed. Dietary analysis showed that higher intake of monounsaturated fats and higher expenditure of calories lowered the risk of gallstones, while higher consumption of refined sugars and saturated fat were directly related to gallstone formation. Particularly interesting was the finding that saturated-fat intake appears to have a stronger relationship to gallstone formation in men than women, Trevisan said. Women had higher rates of gallstones at the first three quartiles of saturated fat consumption, but their risk increased slowly as consumption increased. However, the risk doubled for men at each quartile of consumption and at the highest quartile, men were at a higher risk of developing gallstones than women. Source: University at Buffalo Use of estrogen therapy may increase risk for gallbladder disease Cholelithiasis (gallstones in the gallbladder) is estimated to affect between 10 percent and 15 percent of the U.S. population, with one million new diagnoses yearly. Researchers conducted this study to determine the effect of estrogen therapy in postmenopausal women on gallbladder disease outcomes. The researchers found that both trials showed greater risk of any gallbladder disease or surgery with estrogen: 67 percent increased risk with use of CEE; 59 percent increased risk with use of E + P. Both trials indicated a higher risk for cholecystitis (inflammation of the gallbladder): 80 percent increased risk with CEE; 54 percent increased risk with E + P; and for cholelithiasis, a 86 percent greater risk with CEE; a 68 percent increased risk for estrogen users. Among women with hysterectomy(Excision of the uterus), CEE contributed to 31 excess events per 10,000 women annually. E + P contributed to an excess of 20 events per 10,000 women annually. Source: JAMA and Archives Journals

Back