Gallbladder polyp

Gallbladder polyps are a common clinical findings occurring in 5% of patients who often have cross-sectional imaging for non-specific abdominal symptoms.

When encountering patients with gallbladder polyps, it is important to note what type of polyp is described. While “true” polyps are adenomatous, gallbladder polyps are often non-epithelial growths and, in fact, about 70% of polyps are cholesterol polyps that have no malignant potential.

Adenomas are uncommon and constitute approximately 8% of all gallbladder polyps. Less common polypoid lesions include gallbladder adenocarcinomas, inflammatory polyps, gallstones masquerading as polyps and heterotopic tissue.

Epidemiology
Polypoid lesions of the gallbladder affect approximately 5% of the adult population. The causes are uncertain, but there is a definite correlation with increasing age and the presence of gallstones (cholelithiasis). Most affected individuals do not have symptoms. The gallbladder polyps are detected during abdominal ultrasonography performed for other reasons.

The incidence of gallbladder polyps is higher among men than women. The overall prevalence among men of Chinese ancestry is 9.5%, higher than other ethnic types.

Risk Stratification
After considering the type of polyps, the risk of development of cancer should be determined.

Most demographic data suggest that men and women have an equal propensity to develop adenomatous polyps, however, one study found that men had an increased risk of polyp development.

In addition, several studies have noted that patients with primary sclerosing cholangitis (PSC) that have polyps are more likely to develop adenocarcinoma.

Finally, patients with advancing age may be predisposed to have cancer because some data suggests that gallbladder polyps, like colonic polyps, have an adenoma-to-carcinoma sequence and, therefore, advancing age would permit malignant transformation.

Pathomorphology
Morphology and size have long been deemed important features of gallbladder polyps.

A “ten millimeter rule” for gallbladder polyps is often cited as a reason for cholecystectomy because polyps larger than 10 mm have an increased risk of cancer. Several caveats should be kept in mind when considering the size and morphology of gallbladder polyps.


 * Polyps less than 5 mm rarely, if ever, harbor carcinoma.


 * Polyps greater than 15 mm may have cancer cells in up to 70% of specimens.


 * Polyps that are 5-15 mm must be carefully followed; with a risk of malignancy up to 22% in these patients. Finally, sessile polyps are more likely malignant than pedunculated polyps.

Symptoms
Most polyps do not cause noticeable symptoms. Gallbladder polyps are usually found incidentally when examining the abdomen by ultrasound for other conditions, usually abdominal pain.

Diagnosis

 * Gallbladder polyps are typically identified on ultrasonography, which has a sensitivity and specificity of over 90%.

Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology


 * ERCP (Endoscopic Retrograde Cholangiopancreatography)
 * Contrast enhanced CT may aid in the diagnosis with an overall accuracy of 87% for cancer.
 * HIDA Scan (Cholescintigraphy): Hepatobiliary iminodiacetic acid scan
 * FDG-PET adds little to the CT.


 * Importantly, endoscopic ultrasound, which permits detailed evaluation of the gallbladder wall, has excellent diagnostic capabilities and should be used for indeterminate polyps of 5-15 mm.

Treatment
Clinical decision-making for gallbladder polyps is rather straightforward since the options include surveillance versus cholecystectomy.

Cholecystectomy should be considered in patients with polyps greater than 15 mm and smaller polyps that are sessile or found in patients with PSC. If the polyp is less than 15 mm and surveillance is the management of choice then re-evaluation should occur every 3-6 months because some studies suggest that polyps can increase in size 4-fold in 12 months.

If the rate of growth is nil, then surveillance can be stopped after 2 years.

If cholecystectomy is the treatment plan then one should consider the benefits of open versus laparoscopic cholecystectomy. Sentiment exists that laparoscopic cholecystectomy should not be performed if there is evidence of cancer because laparoscopic gallbladder cancer surgery is often complicated by port-site recurrence.

In one study, 16 patients with gallbladder polyps followed for 4 years had no recurrence. If the specimen demonstrates cancer that invades the muscular wall then radical cholecystectomy should be performed.

Prognosis and Complications
When selecting cholecystectomy over surveillance, it is important to know the complications of cholecystectomy.

In a large study of nearly 23,000 cholecystectomies, the local complication rate was 7%.

Systemic complications were observed in 2.3% of patients. Bile duct injury occurred in 0.3% of patients. Factors important in the outcome include body mass index, male gender and surgeon experience.