Gallbladder polyps are abnormal growths projecting from the inner lining of the gallbladder wall. These lesions are a common incidental finding during abdominal imaging, with most people never experiencing symptoms. The medical challenge lies in distinguishing benign polyps from the small percentage that have the potential to become malignant. This differentiation is based primarily on a polyp’s size and specific features, guiding the decision between observation or surgical removal.
Defining Gallbladder Polyp Types
Gallbladder polyps are broadly categorized into two groups: non-neoplastic, which are overwhelmingly benign, and neoplastic, which possess malignant potential. Non-neoplastic polyps account for approximately 95% of all cases and are not considered true tumors.
The most common type is the cholesterol polyp, representing 60% to 90% of all gallbladder polyps. These are deposits of cholesterol and fat clinging to the wall, a condition known as cholesterolosis. Other non-neoplastic types include inflammatory polyps, which form as scar tissue, and adenomyomatosis, a benign overgrowth of the lining.
Neoplastic polyps, such as adenomas, are true tumors arising from the glandular tissue. While rare, these lesions can progress into gallbladder cancer, specifically adenocarcinoma. Adenomas represent the precancerous lesions in the polyp-cancer sequence. Management depends on estimating the likelihood that a polyp is one of these higher-risk neoplastic types.
Initial Assessment and Diagnostic Imaging
Gallbladder polyps are typically discovered incidentally when a patient undergoes abdominal imaging. The primary diagnostic tool for identifying and characterizing these growths is transabdominal ultrasound (TAUS). Ultrasound is non-invasive and provides real-time images, allowing clinicians to measure the polyp’s largest dimension and assess its appearance.
During the initial assessment, the size of the polyp is meticulously measured, as this is the single most important factor in risk stratification. Imaging also notes the polyp’s morphology, identifying whether it is sessile (flat with a broad base) or pedunculated (attached by a thin stalk). A sessile shape carries a higher risk of malignancy.
Other features assessed include the presence of multiple polyps versus a single one, as single polyps are more likely to be malignant. Secondary imaging, such as Endoscopic Ultrasound (EUS) or CT scans, may be used to evaluate complex cases or to look for signs of invasion into the gallbladder wall. This initial imaging gathers data points to place the patient into the correct risk category.
Criteria for Watchful Waiting
Surveillance, often called “watchful waiting,” is the standard approach for the majority of small, low-risk gallbladder polyps. For an asymptomatic patient without other risk factors, polyps measuring 5 millimeters or less generally require no follow-up, as the risk of malignancy is extremely low.
For polyps measuring between 6 millimeters and 9 millimeters, surveillance with follow-up ultrasound is recommended. This monitoring protocol usually involves an initial ultrasound at six months, followed by annual scans for two to five years. This serial imaging ensures the polyp remains stable in size.
Polyps are considered stable if they show minimal or no growth. Rapid growth is a key trigger for a change in management, often defined as an increase of 2 millimeters or more within two years, or 4 millimeters or more within twelve months. This rapid growth warrants a re-evaluation for possible removal.
If the polyp is asymptomatic, small, and has a pedunculated appearance, it is likely a benign cholesterol polyp. Continued monitoring is a safe strategy in these low-risk individuals, avoiding an unnecessary operation.
Indicators for Surgical Intervention
The decision to proceed with active treatment, cholecystectomy (gallbladder removal), is indicated when the risk of malignancy outweighs the risk of surgery. The most significant indicator for immediate surgical consultation is a polyp size of 10 millimeters (1 centimeter) or larger. Polyps in this range have a substantially increased probability of being neoplastic or harboring cancerous cells.
For polyps measuring 15 millimeters or more, surgical removal is strongly recommended regardless of other factors, as the risk of malignancy is high. A rapid growth rate of any polyp, such as an increase of 4 millimeters or more within a year, is a clear sign to proceed with surgery. This rapid enlargement suggests aggressive biological behavior.
Certain high-risk patient factors mandate surgical intervention even for polyps smaller than 10 millimeters. For example, any polyp found in a patient with Primary Sclerosing Cholangitis (PSC) is an indication for removal due to the elevated background risk of gallbladder cancer. Patients who are symptomatic, experiencing biliary pain or cholecystitis attributed to the polyp, are also candidates for surgery.
Other concerning features that lower the size threshold include sessile morphology, concurrent gallstones, or age over 50 years. When these factors are present, a polyp in the 6-millimeter to 9-millimeter range may trigger a recommendation for cholecystectomy. The presence of focal wall thickening adjacent to the polyp on imaging also raises suspicion and indicates the need for surgical removal.