Gallbladder polyps are found in roughly 1% to 5% of people who undergo an abdominal ultrasound, making them a relatively common incidental finding. One large screening study documented polyps in 1.4% of all subjects, with men slightly more affected (1.7%) than women (1.1%). Most of these polyps are harmless growths that never cause symptoms or require treatment.
Who Gets Gallbladder Polyps
Gallbladder polyps can appear at any age, but they peak in the 36 to 45 age range. In that group, prevalence jumps noticeably: 4.7% of men and 2.1% of women had polyps detected on ultrasound. Men are consistently more likely to have them than women across all age groups, which is the opposite pattern of gallstones, where women are at higher risk.
Obesity is an independent risk factor regardless of whether a person has other metabolic problems like high blood sugar or abnormal cholesterol. But metabolic health matters on its own too. In one large study, people who were a normal weight but had metabolic issues like high blood pressure, diabetes, or abnormal lipids also had a higher risk of developing polyps. The prevalence of polyps 5 mm or larger ranged from 2.4% in metabolically healthy, non-obese individuals up to 4.0% in those who were both obese and metabolically unhealthy.
Most Polyps Are Cholesterol Deposits
The vast majority of gallbladder polyps are not true growths. Cholesterol polyps, which are essentially cholesterol deposits stuck to the gallbladder wall, account for 60% to 90% of all cases. These have zero cancer potential. They form when excess cholesterol in bile accumulates on the inner lining, creating small, often multiple bumps that look like polyps on ultrasound.
Other non-cancerous types include adenomyomas (25% to 40% of non-neoplastic polyps) and inflammatory polyps (about 10%), which develop from chronic irritation of the gallbladder lining. True neoplastic polyps, the kind that are either precancerous or cancerous, are rare. Adenomas make up 4% to 8.9% of all gallbladder polyps. Actual cancer found within a polyp has an incidence of just 0.57% across large studies.
How Polyps Are Detected
Nearly all gallbladder polyps are discovered by accident during an ultrasound ordered for something else, like abdominal pain, liver screening, or a general checkup. Transabdominal ultrasound is the standard tool, with a sensitivity of about 83% and a specificity of 96% for identifying true polyps. The negative predictive value is 99.7%, meaning if an ultrasound doesn’t show a polyp, it’s almost certainly not there.
The positive predictive value, however, is only about 15%. That means most things ultrasound flags as polyps turn out to be something else on closer inspection. One study of patients who went on to have their gallbladder removed found that 42% of polyps seen on ultrasound had no corresponding polyp in the surgical pathology report. All of those “phantom” polyps had measured 6 mm or smaller on the original scan. Of the cases where a polyp was confirmed after surgery, cholesterol polyps accounted for the overwhelming majority.
When Size Matters
The single most important factor in determining what happens next is the polyp’s size. The thresholds are straightforward:
- Under 10 mm: These are almost always benign. If you have no symptoms, the standard approach is periodic ultrasound monitoring to check whether the polyp grows. Small polyps that cause symptoms like pain may still warrant removal.
- 10 to 20 mm: Polyps in this range are considered possibly malignant. Cancer found at this size is usually still early stage, and surgical removal of the gallbladder is generally recommended.
- Over 20 mm: Polyps this large are usually malignant and require surgical removal with more extensive evaluation.
A few situations change the calculus regardless of size. People with primary sclerosing cholangitis, a chronic liver condition, face a much higher cancer risk and are typically advised to have the gallbladder removed if any polyp is found. Having gallstones alongside a polyp also increases concern, because gallstones themselves carry an independent cancer risk.
What the Cancer Risk Actually Looks Like
The numbers are reassuring for most people. Out of more than 5,400 gallbladder polyps analyzed in a systematic review, malignant polyps accounted for just 0.57%. True polyps (adenomas and other neoplastic growths with actual cancer potential) made up only 0.60% of cases. The rest were cholesterol deposits, inflammatory polyps, or other benign tissue with no ability to become cancer.
This means that for every 200 people told they have a gallbladder polyp, roughly one will have something that turns out to be malignant. Your individual risk depends heavily on the polyp’s size, whether it appears to be growing on follow-up scans, and whether you have additional risk factors like the conditions mentioned above. A small, stable polyp found on a routine scan is overwhelmingly likely to be a harmless cholesterol deposit that will never affect your health.