Causes and Risk Factors of Gallstones

gallstones causes and risk factors
Illustration by Joshua Seong. © Verywell, 2018. 

Although scientists aren't entirely sure why and how gallstones form, they seem to occur when your bile has too much cholesterol, too much bilirubin, not enough bile salts, or when your gallbladder is functioning abnormally. Some people are more likely to have risk factors for gallstones too, as age, obesity, certain diseases, and dieting are risk factors.

Common Causes

Gallstones develop, perhaps obviously, in the gallbladder, a pear-shaped organ beneath the liver on the right side of the abdomen. The gallbladder is about 3 inches long and 1 inch wide at its thickest part, and it stores and releases bile into the intestine to aid digestion.

Bile is a fluid made by the liver that helps in digestion. Bile contains substances called bile salts that act like natural detergents to break down fats in the food we eat. As food passes from the stomach into the small intestine, the gallbladder releases bile into the bile ducts. These ducts, or tubes, run from the liver to the intestine. Bile also helps eliminate excess cholesterol from the body. The liver secretes cholesterol into the bile, which is then eliminated from the body via the digestive system.

Most researchers believe at least one of four conditions is necessary to form gallstones:

  1. Excess cholesterol in your bile: Bile becomes supersaturated with cholesterol, which means it contains more cholesterol than your bile can dissolve. This can result in the cholesterol crystallizing and eventually turning into stones.
  1. Excess bilirubin in your bile: There are certain health conditions that can lead to too much bilirubin in your bile, including liver cirrhosis, specific genetic blood disorders, and infection in your biliary tract. Too much bilirubin can lead to pigment gallstones.
  2. Too few bile salts in your bile: This can result in gallstones either because you don't have enough bile salts to break down the cholesterol in your bile or as a result of having too much cholesterol in your bile for the bile salts to dissolve.
  1. Abnormal gallbladder functioning: The gallbladder doesn't contract enough to empty its bile regularly or fully, which can result in your bile becoming concentrated.

Genetics

If you have a family history of gallstones, your chances of developing them are greater. However, multiple studies have shown that genes only make up about 25 percent of the overall risk for developing gallstones.

If you're Native American, there may be a genetic predisposition to secrete higher levels of cholesterol in your bile.

Lifestyle Risk Factors

There are a number of lifestyle risk factors that may contribute to gallstones, including obesity, rapid weight loss, and dieting.

Obesity

Obesity is a strong risk factor for gallstones. Scientists often use a mathematical formula called body mass index (BMI) to define obesity (BMI = weight in kilograms divided by height in meters squared). The more obese you are, the greater your risk of developing gallstones.

Several studies have shown that women with a high BMI are almost three times as likely to develop gallstones as women with a healthy BMI.

Why obesity is a risk factor for gallstones is unclear, but researchers believe that in obese people, the liver produces too much cholesterol.

The excess cholesterol leads to supersaturation in the gallbladder.

Losing Weight Rapidly

People who lose a lot of weight rapidly are at greater risk of developing gallstones. In fact, gallstones are one of the most medically important complications of voluntary weight loss. The relationship of dieting to gallstones has only recently received attention.

Studies have also shown that obese people develop gallstones while on a very low-calorie diet. Very low-calorie diets are usually defined as those containing 800 calories a day, often composed of food that is in liquid form and taken for a prolonged period, typically 12 to 16 weeks.

The gallstones that develop in people on very low-calorie diets are usually silent and don't produce any symptoms. However, about a third of the dieters who developed gallstones in the studies did have symptoms and a proportion of them required gallbladder surgery.

Gallstones are also common among obese patients who lose weight rapidly after gastric bypass surgery, in which the size of the stomach is reduced, preventing the person from overeating. Gallstones are most likely to occur within the first few months after surgery.

Dieting

Researchers believe dieting may cause a shift in the balance of bile salts and cholesterol in the gallbladder. The cholesterol level is increased and the amount of bile salts is decreased. Going for long periods without eating (skipping breakfast, for example), a common practice among dieters, may also decrease gallbladder contractions. If the gallbladder does not contract often enough to empty out the bile, gallstones may form.

If substantial or rapid weight loss increases the risk of developing gallstones, more gradual weight loss would seem to lessen the risk of getting gallstones. However, studies are needed to test this theory.

Some very-low-calorie diets may not contain enough fat to cause the gallbladder to contract enough to empty its bile. A meal or snack containing approximately 10 grams (one-third of an ounce) of fat is necessary for the gallbladder to contract normally. But again, no studies have directly linked a diet's nutrient composition to the risk of gallstones.

Also, no studies have been conducted on the effects of repeated dieting on gallstone formation, through a pattern of repeatedly losing and gaining weight has been shown to possibly increase your chances of developing gallstones.

Other Lifestyle Factors

Other lifestyle factors that may increase your chances of developing gallstones include:

  • A diet that's high in fat, high in cholesterol, and/or low in fiber
  • Not getting enough exercise
  • Fasting, which slows down your gallbladder's movement, allowing cholesterol to collect

Other Risk Factors

Other risk factors for gallstones include:

  • Age 40 or over
  • Gender (women are at higher risk than men)
  • Ethnicity, especially Native American and Mexican American
  • High triglyceride levels
  • Low high-density lipoprotein (HDL) cholesterol
  • Taking cholesterol-lowering drugs
  • Diabetes
  • Crohn's disease in the terminal ileum
  • High estrogen levels from pregnancy, hormone replacement therapy, or birth control pills
  • Liver disease
  • Bile duct infection
  • Cirrhosis
  • Anemia

When Gallstones Are an Emergency

Gallstones can lead to serious complications. Some symptoms that you should discuss with your doctor immediately include gallbladder attacks that are accompanied by sweating, chills, fever, jaundice or clay-colored stools. If you have severe abdominal pain accompanied by vomiting or diarrhea, you should seek medical attention immediately.

Sources:

Johns Hopkins Medicine. Gallstones.

Mayo Clinic Staff. Gallstones. Mayo Clinic. Updated November 17, 2017.

National Institute of Diabetes and Digestive and Kidney Diseases.  Dieting and Gallstones. National Institutes of Health. U.S. Department of Health and Human Services. Updated November 2017.

National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms and Causes of Gallstones. National Institutes of Health. U.S. Department of Health and Human Services. Updated November 2017.

Portincasa P, Di Ciaula A, Grattagliano I. Preventing a Mass Disease: The Case of Gallstones Disease: Role and Competence for Family Physicians. Korean Journal of Family Medicine. 2016;37(4):205-213. doi:10.4082/kjfm.2016.37.4.205.