Gallstones Explained: What They Are, Why They Form, Who Gets Them and When They Need Surgery
By Bridget Nolan | Medically reviewed by Mr Anand Verma, FRCS (Gen Surg)
Published April 6, 2026 · 5 min read
Key takeaways
- Gallstones are hard, pebble-like pieces that form in the gallbladder out of bile, most of them cholesterol stones and a minority pigment stones made from bilirubin.
- They are common: around 10 to 15% of adults in Western populations have them, more often women, and the rate rises with age.
- Roughly 80% of gallstones cause no symptoms and are found by chance; these silent stones are usually left alone.
- The classic symptom is biliary colic, a severe gripping pain high in the upper right abdomen, often after a fatty meal, lasting minutes to a few hours.
- Once stones start causing symptoms the yearly risk of a complication runs at about 1 to 4%, which is why symptomatic stones are usually treated rather than watched.
Gallstones are hard, pebble-like pieces of solid material that form inside the gallbladder, the small pear-shaped organ tucked under the liver that stores and concentrates bile. Most of them are cholesterol stones, made when the bile holds more cholesterol than it can keep dissolved; a minority are pigment stones, built from bilirubin. They can be as small as a grain of sand or as large as a golf ball, and many people have several at once1.
I carried mine for who knows how long without the faintest idea they were there, until one of them shifted and I spent a fortnight blaming my dinner. This is the plain account of what gallstones actually are: why they form, how common they are, who tends to get them, and the point at which they stop being a quiet passenger and start meaning surgery. If you have already had that first attack, the specifics are in gallbladder attack symptoms.
What are gallstones?
Gallstones are stones that form out of bile, the greenish-brown fluid the liver makes to help digest fat, which is stored and concentrated in the gallbladder between meals. They fall into two broad types: cholesterol stones, which make up the large majority in Western countries and are usually yellow-green, and pigment stones, which are smaller, darker, and made from bilirubin2.
The gallbladder itself is a reservoir, not a factory. It sits under the liver and squeezes a dose of stored bile into the small intestine when a fatty meal arrives. Stones form in that stored, concentrated bile, which is why they collect in the gallbladder rather than in the liver above it. The medical name for having them is cholelithiasis, and it is one of the commonest reasons anyone ends up in a general surgeon’s clinic.
Why do gallstones form?
Gallstones form when the balance of the bile tips: most often when there is too much cholesterol in it for the bile to keep dissolved, so the excess crystallises and, over months to years, builds into stones. Pigment stones form for a different reason, when there is too much bilirubin, which happens in some blood and liver conditions3.
Two other things push the process along. If the gallbladder does not empty fully or often enough, the bile sits and stagnates, giving crystals time to gather. And the exact chemistry of a person’s bile, how saturated it runs with cholesterol, is set partly by the liver and partly by weight, diet and hormones over the long term. This is the honest reason a rich meal does not “give” you gallstones on the spot: the meal triggers the attack, but the stones were quietly assembling long before, from the make-up of the bile itself.
How common are gallstones?
Gallstones are very common: around 10 to 15% of adults in Western populations have them, they are found more often in women, and the rate rises steadily with age. Most of those stones never cause a moment’s bother1.
The striking figure is how quiet they usually are. Roughly 80% of gallstones are silent, meaning they produce no symptoms at all and are found only by chance, often on a scan ordered for something else entirely2. That is worth holding onto if a scan has just turned up stones you never suspected: having gallstones and having a gallbladder problem are not the same thing, and the silent majority are usually left exactly where they are, as covered in silent gallstones.
Who gets gallstones?
Gallstones are more likely in women, in people over 40, and in anyone carrying excess weight, with the risk also raised by rapid weight loss, pregnancy, a family history of stones, diabetes, and certain ethnic backgrounds. No single factor guarantees them, and plenty of people with none of the classic risks still form stones3.
The reasons behind the list mostly come back to bile chemistry. Female hormones, including those in pregnancy and some contraceptives, nudge the bile towards holding more cholesterol; losing weight very fast releases a surge of cholesterol into the bile; and a strong family history points to an inherited tendency in how the liver handles it. Age simply adds years for stones to accumulate. It is a genuinely ordinary condition, which is part of why so many people, myself included, are caught off guard when a silent stone finally speaks up.
Do gallstones cause symptoms?
Most gallstones cause no symptoms, but when they do the classic one is biliary colic: a severe, gripping pain high in the upper right abdomen, often coming on after a fatty meal and lasting from a few minutes to a few hours. The pain comes from a stone temporarily blocking the gallbladder’s outlet as it tries to squeeze4.
Mine did not read like a textbook. It arrived an hour after a curry as a deep band of pain under my right ribs, and because it eased by morning I decided it was indigestion and did it three more times over two weeks before I went in. That is a common story, and it is why the fuller version is in the attack that sent me to hospital. Beyond simple colic, stones can cause more serious trouble: an inflamed, infected gallbladder (cholecystitis), jaundice if a stone drops into the main bile duct, and pancreatitis5. Any severe or persistent pain, fever, or yellowing of the skin or eyes is a reason to be seen urgently, not to wait it out as I did.
When do gallstones lead to surgery?
Gallstones are usually only treated once they start causing symptoms or a complication, because from that point the risk of further trouble runs at roughly 1 to 4% a year, which tips the balance towards surgery. For symptomatic stones, NICE recommends removing the gallbladder by keyhole surgery, the operation called a laparoscopic cholecystectomy5.
The reason the whole organ comes out, rather than just the stones, is that the tendency to form stones lives in the bile, so scooping the stones out would simply leave the gallbladder to make more. The standard operation is done through three or four small cuts of about 0.5 to 1 cm; an open operation, through a single larger cut of about 10 to 15 cm under the right ribs, is kept for when keyhole is unsafe or not possible. The gallbladder is not essential, and the liver keeps making bile without it. If you are weighing all this up, the whole picture sits in the pillar guide to gallbladder removal, and the question of whether your own stones need treating at all is worked through in do I need my gallbladder removed.
References
- Definition & Facts for Gallstones, NIDDK. ↩
- Gallstones (Cholelithiasis): Symptoms, Causes & Treatment, Cleveland Clinic. ↩
- Symptoms & Causes of Gallstones, NIDDK. ↩
- Gallstones, NHS. ↩
- Gallstone disease: diagnosis and management (CG188), NICE. ↩
Common questions
What exactly are gallstones made of?
Gallstones are hardened pieces of the bile stored in the gallbladder. Most are cholesterol stones, formed when there is more cholesterol in the bile than it can keep dissolved. A smaller number are pigment stones, made from bilirubin, the substance that gives bile and stool their colour. They range from a grain of sand to several centimetres, and many people have more than one.
How common are gallstones?
Very common. Around 10 to 15% of adults in Western populations have gallstones, more often women, and the rate climbs with age. Most of these stones never announce themselves: roughly 80% are silent, causing no symptoms at all, and are discovered by chance on a scan done for another reason.
Do gallstones always cause pain?
No. About 80% of gallstones are silent and cause no symptoms, so many people carry them for years without knowing. When stones do cause trouble it is usually biliary colic, a severe gripping pain high in the upper right abdomen, often coming on after a fatty meal and lasting from a few minutes to a few hours. Stones can also trigger inflammation, jaundice or pancreatitis.
Who is most likely to get gallstones?
Risk is higher in women, in people over 40, and it rises with obesity, rapid weight loss, pregnancy, a family history of stones, diabetes, and some ethnic backgrounds. Cholesterol stones in particular are linked to the chemistry of the bile rather than to eating too many rich meals, though diet and weight play a part in that chemistry over time.
Can gallstones go away on their own?
Very rarely. Once formed, gallstones almost never dissolve by themselves. Tablets that dissolve cholesterol stones and shockwave treatment exist, but they work slowly, suit very few people, and the stones commonly return, because the tendency to form them sits in the liver's bile. That is why removing the gallbladder is the definitive treatment for stones that are causing symptoms.
If my gallstones are silent, do I need surgery?
Usually not. Silent, symptom-free stones are generally left alone rather than operated on, with selected exceptions a surgeon judges case by case. Surgery is normally offered once stones start causing symptoms or a complication, because from that point the yearly risk of further trouble runs at about 1 to 4%. Whether to operate is a decision for a surgeon who can examine you.
Written by Bridget Nolan. Medically reviewed by Mr Anand Verma, FRCS (Gen Surg).
Our guides are written from personal experience and reviewed by a qualified clinician for accuracy. Read our editorial policy.