A gallstone is a hardened deposit that forms inside your gallbladder, a small organ tucked beneath your liver that stores bile. These stones range from as small as a grain of sand to as large as a golf ball, and most people who have them never know it. Each year, only about 2 out of every 100 people with silent gallstones develop symptoms, meaning the majority carry them for years or even a lifetime without trouble.
How Gallstones Form
Your liver produces bile, a digestive fluid that helps break down fats. The gallbladder stores this bile and releases it into your small intestine after you eat. Gallstones develop when the chemical balance of bile tips out of proportion. The most common scenario: bile becomes oversaturated with cholesterol. When there isn’t enough bile acid to keep cholesterol dissolved, the excess cholesterol begins to crystallize. These tiny crystals clump together over time, gradually growing into solid stones.
A sluggish gallbladder makes the problem worse. If the gallbladder doesn’t empty efficiently, bile sits around longer than it should, giving crystals more time to form and merge. This is one reason obesity raises gallstone risk: people carrying significant extra weight tend to have higher cholesterol levels in their bile and gallbladders that don’t contract as well.
Types of Gallstones
There are two main types. Cholesterol stones are the most common in Western countries, making up roughly 80% of cases. They’re typically yellow-green and form when bile contains more cholesterol than it can dissolve. Interestingly, cholesterol tends to concentrate in the outer layers of these stones, while pigment material collects at the core.
Pigment stones are smaller and darker, usually black or dark brown. They form when bile contains too much bilirubin, a substance your body produces when it breaks down old red blood cells. Conditions that cause your body to destroy red blood cells faster than normal, such as certain blood disorders or liver cirrhosis, increase the risk of pigment stones. Both types share the same basic chemical ingredients (cholesterol, calcium compounds, and bilirubin) but in very different proportions.
Who Gets Gallstones
Gallstones are common. Claims-based data from 2019 show that prevalence ranges from about 0.7% among commercially insured adults to over 2% among Medicare beneficiaries, though these numbers only capture people who sought medical care. The true number of people living with gallstones, including silent ones, is much higher.
Women develop gallstones more often than men, particularly during reproductive years. Estrogen increases cholesterol levels in bile and slows gallbladder movement, which is why pregnancy, hormone replacement therapy, and birth control pills all raise the risk. Other well-established risk factors include age over 40, a family history of gallstones, and Native American or Mexican American heritage.
Weight plays a major role, especially for women. People with obesity tend to produce bile with higher cholesterol concentrations. Carrying extra fat around the waist appears to be a stronger risk factor than carrying it around the hips and thighs. Paradoxically, losing weight too quickly also triggers gallstones. When you fast or drop weight rapidly, your liver dumps extra cholesterol into bile, and your gallbladder may stop emptying properly. Weight-loss surgery and very low-calorie diets are particular risk factors. Even weight cycling, repeatedly losing and regaining weight, increases your chances, with larger swings in weight carrying greater risk.
What a Gallstone Attack Feels Like
Most gallstones sit quietly in the gallbladder and cause no symptoms at all. Problems start when a stone shifts and blocks the duct that drains the gallbladder. This triggers what’s called biliary colic: a sudden, intense pain in the upper right side of your abdomen, sometimes radiating to your right shoulder or back. The pain comes from the duct going into spasm as it tries to push past the obstruction.
Attacks often strike at night, possibly because lying down allows stones to slide more easily toward the duct opening. The pain typically builds to a peak over minutes and can last anywhere from 30 minutes to a few hours. It often hits after a fatty meal, since fat triggers the gallbladder to squeeze. If the stone passes back into the gallbladder or through the duct, the pain fades. If it doesn’t, and pain lasts beyond three hours, that’s a sign of acute cholecystitis, where the gallbladder itself becomes inflamed.
How Symptoms Progress Over Time
If you’ve been told you have gallstones but haven’t had symptoms, the odds are in your favor. A large meta-analysis found that about 10% of people with silent gallstones develop symptoms within 5 years. At 10 years, that number rises to roughly 19%, and by 15 years, about 26%. So even after a decade and a half, roughly three out of four people with incidental gallstones still haven’t had a problem. This is why surgery isn’t typically recommended for stones found by accident during imaging for something else.
Complications Worth Knowing About
When gallstones do cause trouble, they can occasionally lead to serious complications. Acute cholecystitis happens when a stone stays lodged in the duct, cutting off bile flow and causing the gallbladder wall to swell and potentially become infected. Symptoms include persistent pain, fever, and tenderness in the upper right abdomen.
If a stone travels further and blocks the common bile duct (the tube shared by the liver and pancreas), it can trigger gallstone pancreatitis. This is an inflammation of the pancreas and it’s a medical emergency. The hallmark symptom is severe pain in the upper left abdomen that may radiate to the back, chest, or shoulder, along with nausea and vomiting. More advanced signs include a swollen belly, fever, jaundice (yellowing of the skin and eyes), rapid heartbeat, and low blood pressure. Gallstone pancreatitis requires hospital treatment.
How Gallstones Are Diagnosed
An abdominal ultrasound is the go-to first test. It’s painless, quick, and good at spotting stones sitting in the gallbladder. However, ultrasound is less reliable when the question is whether the gallbladder itself is acutely inflamed. In one study, ultrasound had only 26% sensitivity for detecting acute cholecystitis, meaning it missed the diagnosis nearly three-quarters of the time.
When acute cholecystitis is suspected but the ultrasound is inconclusive, a HIDA scan is often the next step. This involves injecting a small amount of radioactive tracer into a vein and watching whether it flows through the liver and into the gallbladder normally. If the gallbladder doesn’t fill, it suggests a blocked duct. HIDA scans are significantly more accurate for this purpose, with about 87% sensitivity. CT scans may also be used, particularly when pancreatitis or other complications need to be evaluated.
Treatment Options
Surgery to remove the gallbladder, called cholecystectomy, is the standard treatment for gallstones that cause symptoms. It’s almost always done laparoscopically through a few small incisions. Most people go home the same day or the next morning, and recovery typically takes one to two weeks. Because the gallbladder is removed entirely, stones can’t come back. Your liver continues producing bile, it just drips directly into your intestine instead of being stored. Most people adjust without any lasting digestive issues, though some notice looser stools for a few weeks after surgery.
A non-surgical option exists: a bile acid medication that works by slowly dissolving cholesterol stones. But it has significant limitations. Only about 10% of gallstone patients qualify, because the stones need to be small, made of cholesterol, non-calcified, and in a gallbladder that still contracts normally. Even when it works, about half of patients see their stones return within five years. The medication also requires months to years of daily use. For these reasons, surgery remains the treatment of choice for the vast majority of people who need their gallstones addressed.
For people with silent gallstones and no symptoms, the standard approach is simply to leave them alone. Given the low annual rate of symptom development and the small but real risks of any surgery, watchful waiting makes sense for most people in this situation.