Anywhere from 20 to 25 million people in the U.S. have a problem with their gallbladder, a small pear-shaped organ that sits underneath the liver and stores bile, a digestive fluid that helps break down fats.

The most common gallbladder problem is gallstones, crystallized clumps of bile and dissolved cholesterol that form in the gallbladder or bile duct, the tube that carries the bile to the small intestine. Gallstones can cause inflammation and pain, and lots of people have them—up to 20% of women and 10% of men in the U.S. by the age of 60—and they can be as small as a grain of sand or as large as a golf ball.

Women are more likely to develop gallstones, and changes in the sex hormones estrogen and progesterone can slightly increase gallstone production. Estrogen boosts the amount of cholesterol in your bile, and progesterone slows the emptying of the gallbladder. The risk of forming gallstones is increased slightly by pregnancy or even oral contraception, which affect hormone levels.

Most people have these stones with no symptoms, often called "silent stones," and they do not require treatment, but for people experiencing symptoms from gallstones or low-grade gallbladder inflammation, surgery to remove the gallbladder is the most common recommended treatment.

A bit like the appendix, the gallbladder can be removed without harming normal function. However, the body needs to adjust to having bile dump directly into the digestive tract, rather than being released as needed. Digesting fatty meals can be a problem after the surgery.

Gallstones are often detected incidentally while investigating other health problems, according to the American College of Gastroenterology. But if you experience the following signs and symptoms, seek out medical care.

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Abdominal pain

The occasional recurrence of a dull pain by your liver is the most common sign that you have gallstones. The pain often strikes after eating and can last a couple hours before it resolves, says Edward Levine, MD, a gastroenterologist and an associate professor of clinical medicine at Wexner Medical Center at The Ohio State University in Columbus. Pain is typically experienced in the upper right abdomen, near the rib cage, but it can also radiate to the upper back and the center of the abdomen.

Pain following a meal can happen once in a while or after every meal. Known as biliary colic pain, or a gallbladder attack, it can last anywhere from an hour to several hours and is more likely to be triggered by large and fatty meals. This kind of pain comes and goes repeatedly. Chronic, ongoing pain that persists beyond a few hours may also occur, and may suggest a more severe gallbladder issue.

The timing of the pain is important, says Allison Yang, MD, a gastroenterology and hepatology fellow at Brigham and Women’s Hospital in Boston. Pain symptoms typically come within a couple hours after a meal, so if you are experiencing pain sooner, while eating or immediately after, that might be a tip off that it is not gallbladder disease.

Pain relievers don’t help

If either biliary or chronic pain doesn't improve with an OTC pain reliever, it may also be an indication that you have a gallbladder problem. Experiencing little improvement after a change in position, bowel movement, or after passing gas are also indications. "These kind of rule out other things and may help us target the gallbladder more specifically," says Dr. Yang.

Jaundice

Jaundice is a symptom of liver trouble that manifests as a yellowing of the skin and the whites of the eyes, along with symptoms like dark urine and pale colored stools. Jaundice is common in newborns, but it’s also an indication of a gallbladder problem in adults. The gallbladder releases bile into the small intestines through a tube called the cystic duct, which connects to the bile duct. Jaundice occurs when you obstruct these ducts. "If you think of this tube as a hose, if the gallbladder forms a stone and the stone gets stuck inside the tube, there's essentially a stone inside the hose and it causes a blockage," says Dr. Yang.

That blockage can cause bile to build up in the gallbladder and increase the concentration of a yellowish substance called bilirubin.

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Nausea

A lot of people mistake gallbladder problems for an upset stomach, heartburn, or acid reflux. "Sometimes people may mistake gallbladder pain as muscle pain from exercise," says Dr. Yang. But if the nausea or vomiting recurs with repeated episodes of pain after eating, that might be an indication of gallbladder disease. While nausea is not as common a symptom as abdominal pain, if there’s significant nausea or vomiting, those are signs that you should probably go to a physician, urgent care, or the emergency room.

Pancreatitis

If you develop pancreatitis, an inflammation of the pancreas, you should be checked for gallstones, says Dr. Yang. The pancreas sits next to the liver and discharges digestive enzymes into the same area of the digestive tract as bile; because the two ducts meet up near the intestine, a stone in one can affect the function of the other. If a gallstone exits the gallbladder and gets stuck in the pancreatic duct, it can cause inflammation and abdominal pain. Dr. Yang says that if this occurs, doctors usually recommend that the gallbladder be removed. Pancreatitis symptoms can include abdominal pain, nausea and vomiting, a rapid pulse, and a fever.

Obesity or sudden weight loss

These are problems associated with gallstones, and are not necessarily symptoms. Typically the weight or weight loss happens first, and then gallbladder issues develop. Why? People who are obese are at greater risk of gallstones. And while losing weight can help decrease the risk, very rapid weight loss can make you more prone to forming gallstones. "Patients who experience gastric bypass surgery or stapling surgery, when they lose a lot of weight very quickly, that's often associated with forming gallstones," says Dr. Yang.

Pacing is important. Dr. Yang recommends, "slow, steady, healthy weight loss" over crash diets.

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Abnormalities in ultrasound, MRI, HIDA scan

The gallbladder is a hollow organ, and gallstones can show as solid masses in the gallbladder or the bile duct on an ultrasound. This non-invasive test is the usually the first step to investigating problems in the gallbladder, explains Dr. Yang. Doctors can take note of the size of the gallbladder and if any swelling or thickening of the walls has occurred, as those may be signs of inflammation. Other tests include magnetic resonance imaging, or MRIS, which can be more helpful to look at ducts. Finally, a hepatobiliary, or HIDA, scan can show how well the gallbladder is emptying itself. During the test, a radioactive tracer in injected in your arm and used to visualize the ducts. Sometimes these procedures can be helpful when a gallbladder disease diagnosis isn’t clear on an ultrasound. "[The tests] may explain why someone may be having gallbladder symptoms without clearly a stone or something causing obstruction," says Dr. Yang.

While right-sided abdominal pain is a classic symptom of gallbladder disease, sometimes what feels like abdominal pain is actually a heart or lung condition. "People (especially women) may have atypical presentations of heart attacks or other cardiac problems, and these may present as abdominal pain rather than chest pain," says Dr. Yang.

Pneumonia, especially if it is in the lower part of the right lung, Dr. Yang continues, may also feel like right-sided upper abdominal pain. And if you experience fever and chills along with the abdominal pain, it could mean there’s an acute inflammation of the gallbladder that's due to an infection, not gallstones. These symptoms may raise concerns that gut bacteria that are normally present in the intestines have invaded the gallbladder. Dr. Yang says this warrants immediate medical attention and may require surgery.

Overall, if any symptoms recur or persist, patients "should definitely be evaluated by their doctor," Dr. Yang recommends. "They should speak with their doctor to see if they need to be evaluated more urgently in the ER or if they can be seen in the office the next day for further work up."