Gallbladder polyps describe several conditions that present as projections into the gallbladder lumen. They may be asymptomatic, or they may be related to symptoms of cholecystitis (right upper abdominal discomfort, nausea and food intolerances). Often gallbladder polyps are found inadvertently on ultrasound or CT scanning or can be incidentally found on pathologic examination of the gallbladder. These polyps can be true neoplastic growths or pseudopolyps of cholesterol balls clinging to the wall of the gallbladder.
There a few risk factors associated with true gallbladder polyp formation. Some studies suggest conditions such as familial polyposis, Peutz-Jeghers, Gardner syndrome, and hepatitis B may be factors associated with polyp formation. Pseudo or cholesterol polyps can develop when the cholesterol or bile salt content in the bile is high. This leads to condensation of cholesterol clumps which can adhere to the wall of the gallbladder. This condition may be a precursor to gallstone formation and can also at times be seen in conjunction with gallstones. Other factors typically associated with gallbladder diseases such as obesity, sex, weight loss, and diabetes have not been shown to increase the formation of gallbladder polyps.
Factors associated with an increased prevalence of gallbladder polyps is unclear. Studies have shown that 4% to 7% of the population may develop gallbladder polyps. The average age of diagnosis of gallbladder polyps is around 49 years old. However, other studies have found the presence of polyps to be more prevalent in older patients.
The most common type of gallbladder polyps are pseudo or cholesterol polyps. These account for 60% to 90% of all gallbladder polyps. They are not true neoplastic growths, but rather they are cholesterol deposits that form as projections on the inner lumen of the gallbladder wall. They are formed from precipitation of cholesterol or bile salts. Presence of cholesterol polyps may be indicative of pathologic gallbladder disease such as chronic cholecystitis. Inflammatory polyps account for 5% to 10% of all gallbladder polyps. They are associated with inflammation of the gallbladder mucosa and wall. Usually, this type is associated with repeated bouts of cholecystitis and acute biliary colic. Both pseudopolyps and inflammatory polyps carry close to a zero risk of developing a gallbladder cancer. These polyps rarely exceed 1 cm in diameter and are often multiple. True adenomatous gallbladder polyps are considered neoplastic. They are rare and are often associated with gallstones. They can range in size from 5 mm to 20 mm. Once the polyp reaches a size of greater than 1 cm, consideration needs to be made for cholecystectomy, because of the potential malignant increases above 1 cm. Adenomyomatosis is a more common true poly. It has classically been considered a benign lesion of the fundus of the gallbladder. However, recent findings suggest these lesions do have premalignant potential. Malignant polyps tend to be singular and more than 2 cm in diameter.
Two percent to 12% of routine gallbladder pathology specimens may contain gallbladder polyps, but true adenomatous polyps are present in less than 0.5% of all gallbladder specimens. Cholesterol polyps show an increased cholesterol content and are associated with gallbladder cholesterolosis and sludge. Inflammatory polyps exhibit inflammation of the gallbladder wall with Rotatinski- Aschoff bodies, and findings of acute or chronic cholecystitis. True adenomatous polyps have a glandular histology. Malignant polyps can demonstrate cancerous changes characteristic of adenocarcinoma, squamous cell carcinoma, and adenoacanthoma. The degree of malignant differentiation usually correlates to polyp size.
Most gallbladder polyps are asymptomatic. Patients with cholesterol stones related to hypokinetic gallbladder function, cholesterolosis, or stasis may exhibit symptoms of chronic cholecystitis. Right upper abdominal pain, food intolerance, bloating, and nausea may be present. Elicitation of a positive Murphy's sign, pain with deep palpation to the right upper abdomen, is often present. Patients with larger adenomatous lesions may have more severe and persistent right upper abdominal pain. Cases of progressive polyps that have deteriorated into a malignancy may present with jaundice, due to growth and impingement of the common or hepatic bile duct. There may also be a palpable mass in the right upper abdomen.
Gallbladder polyps are often found coincidentally with imaging such as an abdominal CT or an abdominal ultrasound. In cases of patients being worked up for gallbladder disease, the polyps are usually seen on abdominal ultrasound. They may present as a single lesion, or they may be multiple in nature. Polyps can occur in conjunction with gallstones but are often seen in the absence of stones. Differentiation must be made between gallstones and gallbladder polyps. Gallstones are usually mobile, and polyps are fixed to the wall of the gallbladder lumen. Most polyps are hypodense and smaller than 1 cm in diameter. They can appear polypoid or sessile. Singular polyps that have a tissue density and are larger than 1 cm in diameter carry a higher malignant potential.
Gallbladder polyps that have the appearance of pseudo or cholesterol polyps, in asymptomatic patients, can be followed with yearly gallbladder ultrasounds. These patients have a very low malignant risk. If serial ultrasounds reveal that the polyp is enlarging or if the patient becomes symptomatic, then cholecystectomy should be recommended. Patients with symptoms of chronic cholecystitis are usually best treated with laparoscopic or open cholecystectomy. Polyps that are 1 cm or greater in size should undergo cholecystectomy due to the increased risk of developing gallbladder cancer. Early intervention is preferred because an early gallbladder neoplasm has a much higher rate of cure than a more advanced lesion. In fact, stage 0 gallbladder cancer has about an 80% 5-year survival rate, and stage 1 has less than a 50% survival rate. Less than 10% of all gallbladder cancers are diagnosed at stage 1 or lower. More advanced gallbladder cancers require an open cholecystectomy with resection of the gallbladder fossa of the liver along with regional lymph node removal.
The vast majority of gallbladder polyps are asymptomatic and carry a low risk of malignant degeneration. However, a small number of true gallbladder polyps will progress to malignancy. Patients with symptomatic gallbladder polyps or with enlarging polyps should be treated with cholecystectomy. The risks of performing a laparoscopic cholecystectomy are far less than missing a potential adenomatous polyp. It is recommended that if there is any indication of a gallbladder polyp being anything other than a pseudopolyp or cholesterol polyp, that cholecystectomy should be performed.