Citation, DOI & article data
Gallbladder polyps are commonly occurring elevated lesions on the mucosal surface of the gallbladder. The vast majority are benign. They are best characterized on ultrasound as a non-shadowing endophytic growth into the gallbladder lumen.
Gallbladder polyps are relatively frequent, seen in up to 9% of the population 1,7,12,14. The majority are cholesterol polyps.
Cholesterol polyps are most frequently identified in patients between 40-50 years of age and are more common in women (F:M, 2.9:1) 3.
Asymptomatic gallbladder polyps do not seem to raise the risk of gallbladder cancer19. Polyp frequency is the same in those with gallbladder cancer and those without. Gallbladder cancer has equal incidence in those with polyps and those without. Benign polyps may demonstrate annual growth of around 2 mm. There is no evidence for malignant degeneration of polyps. Most malignant polyps are >20 mm.
Typically gallbladder polyps are incidental findings in about 10% of upper abdominal ultrasound examinations. Unless large, polyps are asymptomatic 1,3.
A wide variety of entities appear as polyps and histology is variable:
benign polyps: 95% of all polyps
cholesterol polyps: >50% of all polyps 3,7,14
inflammatory polyps: ~10% 14
other rare entities (see benign tumors and tumor-like lesions of the gallbladder)
neoplastic polyps (2019 WHO Classification of Tumors, 5th edition, Digestive System Tumors):
intra-cholecystic papillary neoplasms (ICPN) account for 6% of gallbladder carcinomas and have a favorable survival rate
ass-forming, endophytic, non-invasive epithelial neoplasms of the mucosa >10 mm
four types: biliary, gastric, intestinal and oncocytoma.
pyloric gland adenomas, present in <0.5% of cholecystectomy specimens may be associated with familial adenomatous polyposis or Peutz-Jeghers syndrome
malignant polyps: 5% of all polyps.; most measure >20mm
adenocarcinoma: ~90% of malignant polyps
and other rare entities including
squamous cell carcinoma
In most instances, predicting histology based purely on imaging is not possible, with the possible exception of cholesterol polyps in some instances (see below), and thus features that are predictive of benign vs malignant disease should be noted (see benign vs malignant features of gallbladder polyps) 1,6,7.
Neoplastic polyps are larger, mean size of 18-21 mm compared to non-neoplastic polyps, mean size of 4-7.5 mm 18.
Ultrasound is the best initial imaging choice and is often able to separate cholesterol polyps from those requiring treatment. General features of gallbladder polyps are a non-shadowing polypoid ingrowth into the gallbladder lumen, which is usually immobile unless there is a relatively long pedunculated component.
General features of polyps include 8:
cholesterol polyps are the most frequent, over 90% are <10 mm, and the vast majority are <5 mm. They often have a single supplying vessel
benign neoplasms or malignant lesions tend to be larger
echogenicity varies with the size
small polyps are echogenic but non-shadowing
larger cholesterol polyps tend to be hypoechoic
small polyps may be adherent to the wall and smooth
larger lesions tend to be pedunculated and granular in outline
Rarely, endoscopic ultrasound may be useful to further assess gallbladder polyps as it may generate higher resolution images 7,8.
Some publications have suggested a useful role in high-resolution ultrasound (HRUS) for categorization of gallbladder polyps with features favoring neoplastic polyps from benign comprising of 16:
size >1 cm
lobulated surface contour
presence of branching vessels seen on color Doppler
hypoechoic internal echo of the polyp
hypoechoic foci within the polyp
CEUS demonstrates vascular characteristics.
CT is often unable to detect small gallbladder polyps. Larger polyps will appear as soft tissue attenuation projections into the lumen of the gallbladder and will demonstrate enhancement similar to that of the rest of the gallbladder. More intense enhancement should be viewed with suspicion, as it is associated with increased vascularity in malignancy.
Treatment and prognosis
Society of Radiologists in Ultrasound guidelines (2021)
The SRU 17 reviewed current evidence and found no link between gallbladder carcinoma and polyps. Most gallbladder cancers arise from flat dysplastic epithelium that thickens as the cancer progresses. They recognize three categories of polyp: non-neoplastic, benign neoplastic and malignant. The follow-up period is shortened to three years. Concerning growth is increased to >4 mm per annum. Slow growth of benign polyps up to 2 mm per annum is common, and conversely, many small polyps disappear. Most malignant polyps are >20 mm. Primary sclerosing cholangitis is an important risk factor for cholangiocarcinoma and gallbladder cancer.
They propose the following guidelines:
extremely low-risk polyps, i.e. pedunculated ball-on-the-wall or thin stalk:
<9 mm: no follow-up
10-14 mm: follow-up at 6, 12 and 24 months
>15 mm: surgical consult
low-risk polyps, i.e. pedunculated with a thick or wide stalk, or sessile:
≤6 mm: no follow-up
7-9 mm follow-up ultrasound at 12 months
10-14 mm: follow-up ultrasound at 6, 12, 24, and 36 months vs surgical consult
>15 mm: surgical consult
intermediate risk: focal wall-thickening >4mm adjacent to polyp:
<6 mm: follow-up at 6, 12, 24, 36 months vs surgical consult
>7 mm: surgical consult
European guidelines (2017)
In 2017 joint guidelines between the European Society of Gastrointestinal and Abdominal Radiology (ESGAR), European Association for Endoscopic Surgery and other Interventional Techniques (EAES), International Society of Digestive Surgery - European Federation (EFISDS) and European Society of Gastrointestinal Endoscopy (ESGE) were published and provide the most up to date and comprehensive guidance 13:
polyp >10 mm: increased risk of malignancy, cholecystectomy recommended
polyp <10 mm
symptoms attributed to the gallbladder: cholecystectomy is suggested if no other cause for the symptoms is determined (polyp may be indicative of underlying occult calculus or inflammation)
if the patient has risk factors* for gallbladder malignancy:
polyp <6 mm
follow-up ultrasound at 6 months, then yearly for 5 years
an increase in size ≥2 mm: consider cholecystectomy
polyp >6 mm: consider cholecystectomy
no risk factors for gallbladder malignancy:
polyp <6 mm: follow-up ultrasound at 1, 3 and 5 years
polyp >6 mm:
follow up ultrasound at 6 months, then yearly for 5 years
an increase in size ≥2 mm: consider cholecystectomy
*Risk factors: >50 years, primary sclerosing cholangitis, Indian ethnicity, sessile polyp (including focal wall thickening >4 mm).
Statistically, gallbladder polyps are common and gallbladder cancer is rare, so very few polyps progress to gallbladder cancer. There is also controversy regarding the development of gallbladder cancer and some suggest that polyps may not progress to cancer 10.
American College of Radiology guidelines (2013)
According to the White Paper of the ACR Incidental Findings Committee II on Gallbladder and Biliary Findings (2013) 11:
≤6 mm: no further evaluation or follow-up necessary 6,10
7-9 mm: yearly follow-up with an ultrasound to ensure no interval growth 15
≥10 mm: surgical consultation for cholecystectomy
if no cholecystectomy, annual follow-up is justified 11
Lower thresholds for follow-up or intervention may be warranted if the patient population is known to have a higher risk of gallbladder carcinoma (e.g. higher incidences in Pakistan, Ecuador, and females in India).
The differential for a gallbladder polyp is limited, and includes 6:
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