Treatment for Indolent Gallbladder Polyps?
Question
What is the appropriate treatment for indolent gallbladder polyps found on
routine echography (ultrasonography)?

Response from Geoffrey L. Braden, MD
Clinical Associate Professor of Medicine, Department of Internal Medicine
and Gastroenterology, MCP Hahnemann University, Philadelphia,
Pennsylvania; Chief, Division of Internal Medicine, Department of Internal
Medicine, Frankford Hospital, Philadelphia, Pennsylvania

The lifetime prevalence of gallbladder polyps ranges from 1% to 4%.[1]
Overall, polyps are much less common than gallstones, and they are usually
discovered as an incidental finding when an ultrasound of the abdomen is
performed for the evaluation of biliary-type abdominal pain or to survey
the liver for focal defects or extrahepatic obstruction.

The evaluation of gallbladder polyps is somewhat hampered by the inability
to directly image the gallbladder mucosa endoscopically. As a result,
management is usually guided by the characteristics of gallbladder polyps
found on ultrasound, {*filter*}cholecystography, and CT scan.

Five types of polyps are found in the gallbladder and the 3 most common
are nonneoplastic.[1] Cholesterol polyps account for 60% of all
gallbladder polyps; they are usually multiple and pedunculated and range
in size from 2-10 mm. These polyps occur as part of focal or generalized
cholesterolosis of the gallbladder and are not neoplasms.

Occasionally, cholesterol polyps can slough off and cause biliary colic
from cystic duct obstruction or acute pancreatitis by blocking the common
bile duct.

Adenomyomas (or adenomyomatosis) represent the second most common type of
gallbladder polyp. These account for 25% of gallbladder polypoid lesions
and are usually solitary, ranging in size from 10-20 mm on average.
Adenomyomatosis is usually found at the fundus of the gallbladder.
Histologically, the lesions cause focal thickening of the gallbladder
wall. They are associated with branching and dilatation of
Rokitansky-Aschoff sinuses and hyperplasia of the muscle layer of the
gallbladder wall. On ultrasound or {*filter*}cholecystography, these lesions
appear as a focal thickening of the gallbladder wall. The dilated and
branching Rokitansky-Aschoff sinuses appear as intramural defects rather
than polyps projecting into the lumen. The only clinical significance of
adenomyomatosis occurs when the disease is segmentally distributed in the
gallbladder, leading to a concentric narrowing or constriction of the
gallbladder lumen. This type of lesion is associated with an increased
incidence of gallbladder cancer, and the gallbladder should be removed
surgically. A study of 3000 surgically resected gallbladders found
gallbladder cancer in 6.4% of gallbladders that contained segmental
adenomyomatosis.[2]

Inflammatory polyps are the third most common type, accounting for 10% of
all gallbladder polyps. As expected, these polyps consist of granulation
tissue and fibrous tissue mixed with chronic inflammatory cells, usually
lymphocytes and plasma cells. They are generally solitary, and range in
size from 5-10 mm.

Collectively, these 3 types of benign focal gallbladder lesions account
for 95% of all gallbladder polyps. With the exception of segmental
adenomyomatosis, clinical and surgical intervention are not indicated.

True adenomas account for 4% of gallbladder polyps and miscellaneous rare
neoplastic lesions account for the last 1%. Adenomas of the gallbladder
are rare and are found in approximately 0.15% of resected gallbladder
specimens.[3] They range in size from 5-20 mm and are usually
pedunculated. These lesions are potentially premalignant, but the
evolution of the adenoma-carcinoma sequence does not apply to the same
extent as it does for colon polyps leading to colon carcinoma. Almost all
adenomas that contain cancer are > 12 mm in size. Adenomas > 18 mm have a
higher incidence of containing invasive gallbladder cancer. Gallbladder
adenomas occur much less commonly than gallbladder cancer; that is, they
occur in approximately a 1:4 ratio.[1] A study from Japan looked at the
adenoma-carcinoma sequence in a series of 1600 surgically resected
gallbladders.[4] Eigh{*filter*} gallbladder adenomas were found and 7 (39%)
contained foci of cancer. All of the adenomas were > 12 mm. Seventy-nine
gallbladder carcinomas were present and 15 (19%) contained residual
adenomatous tissue in the pathology specimen. These data do not fully
address the issue, but it seems likely that the majority of gallbladder
carcinomas probably do not arise from previously benign gallbladder
adenomas.

As mentioned above, miscellaneous neoplasms of the gallbladder represent
the fifth class of gallbladder polyps. These polyps are all rare lesions
and include heterotopic gastric glands, neurofibromas, carcinoid tumors,
leiomyomas, and fibromas. They are usually solitary, benign, and range in
size from 5-20 mm.

The best treatment for gallbladder polyps is to surgically remove the
gallbladder when adenomas >/= 10 mm are present. The problem is that the
majority of lesions of this size that are discovered on ultrasound will be
among 1 of the 3 nonneoplastic types of gallbladder polyps. I would still
recommend an elective cholecystectomy for a healthy patient who had a
lesion >/= 10 mm. This approach minimizes the chance of not treating a
premalignant lesion. Most cholesterol and inflammatory polyps are < 10 mm.
Adenomyomatosis can usually be defined on imaging studies, and I would not
remove the gallbladder unless segmental involvement leading to luminal
narrowing was present. Patients who are at high risk for surgery should
have an ultrasound performed at 6-month intervals. If a polyp grows to >/=
12 mm over time, the gallbladder should be removed if possible.

Endoscopic ultrasound may become the standard of care in the near future
to define the histology of gallbladder polyps. Recent studies have shown a
correlation between endoscopic ultrasound characteristics and the actual
histology of gallbladder polyps.[5,6]

Posted 07/29/2003