A gallbladder polyp is a growth extending from the inner wall of the gallbladder, the small organ located beneath the liver that stores bile. These growths are a relatively common finding, detected in about four to seven percent of adults, often when imaging is performed for unrelated reasons. The vast majority of these polyps are benign and do not cause any symptoms, making their discovery an incidental event. When a 7-millimeter (mm) polyp is found, the primary concern revolves around its potential to be or to become cancerous, which is an assessment largely based on its size and characteristics.
Categorizing Gallbladder Polyps
Polyps are broadly categorized into non-neoplastic (benign) and neoplastic (those with malignant potential) types. Understanding their composition is fundamental to assessing risk, as the type of growth dictates its potential for malignancy. The most frequently encountered type, accounting for 60 to 90 percent of all findings, are cholesterol polyps, which are deposits of cholesterol adhering to the gallbladder wall.
Cholesterol polyps, sometimes called pseudopolyps, are considered harmless and carry virtually no risk of becoming cancerous. Another common non-neoplastic type is the inflammatory polyp, which is scar tissue resulting from chronic inflammation of the gallbladder wall. Neoplastic polyps, though much rarer, include adenomas (true tumors of the lining cells) and, infrequently, early-stage carcinomas.
Ultrasound can identify the presence and size of a polyp, but it generally cannot definitively determine its cellular composition. Because of this limitation, risk stratification relies heavily on the polyp’s size and its growth rate over time. Neoplastic polyps tend to be larger than non-neoplastic ones, which is why a 7mm finding necessitates careful consideration of its other features and patient-specific factors.
Assessing Malignancy Risk Based on Size
Medical consensus places the primary threshold for elevated concern at 10mm (1 centimeter). Polyps 10mm or larger have a significantly higher probability of being malignant, with the risk increasing substantially with size. In contrast, polyps smaller than 10mm, including a 7mm finding, have an extremely low rate of malignancy.
A 7mm polyp falls into the intermediate size category, typically defined as 6mm to 9mm, where the risk of cancer is minimal but requires proactive monitoring. The cancer rate increases slightly in this range compared to polyps under 6mm, but it remains far below the risk associated with polyps 10mm and above. The vast majority of documented gallbladder cancers arising from polyps are found in lesions that are 15mm or larger.
Risk assessment for a 7mm polyp is not based on size alone, as secondary factors can increase the level of concern. These risk factors include a patient’s age over 60, the presence of accompanying gallstones, a diagnosis of primary sclerosing cholangitis (a chronic liver disease), or being of Asian ethnicity. The polyp’s appearance on ultrasound is also important: a sessile (broad-based) shape or associated thickening of the gallbladder wall is more suspicious than a pedunculated (stalk-like) shape. If a 7mm polyp is found without any of these high-risk features, it is generally considered a low-risk finding.
Monitoring and Treatment Guidelines
For an asymptomatic 7mm gallbladder polyp without high-risk features, the standard medical approach is careful surveillance rather than immediate surgical removal. The management protocol focuses on monitoring the polyp’s growth rate and looking for concerning changes over time. This surveillance is typically performed using transabdominal ultrasound at scheduled intervals.
For a low-risk 7mm polyp, guidelines recommend follow-up ultrasound at six months, one year, and then two years. This schedule aims to detect two specific changes that prompt surgical consultation (cholecystectomy, or gallbladder removal). The first indication for intervention is if the polyp grows to reach the 10mm size threshold.
The second indication is rapid growth, defined as an increase in size of 4mm or more within a 12-month period, regardless of the final size. Polyps that grow quickly are viewed with suspicion, although minor size fluctuations (2mm to 3mm) are considered a normal part of the natural history of benign polyps. If a 7mm polyp has high-risk features, such as a sessile shape or primary sclerosing cholangitis, cholecystectomy may be recommended even at this smaller size.