Gallbladder polyps are elevated lesions on the mucosal surface of the gallbladder. The vast majority are benign, but malignant forms are seen. Gallbladder polyps may be detected by ultrasound, CT, or MRI, but are usually best characterised on ultrasound.
Gallbladder polyps are relatively frequent, seen in up to 7% of the population 1,7,12. Over 90% are benign, and 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.
Typically gallbladder polyps are incidentally found on upper abdominal imaging, usually during imaging for upper abdominal discomfort. 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
- adenoma: ~30%, possibly premalignant 4
- inflammatory polyps
- other rare entities (see benign tumours and tumour-like lesions of the gallbladder)
malignant polyps: 5% of all polyps
- adenocarcinoma: ~90% of malignant polyps
- other rare entities including
- metastases to gallbladder
- squamous cell carcinoma
Cholesterol polyps appear as yellow, lobulated, and often pedunculated masses.
Cholesterol polyps are composed of lipid-laden macrophages, covered by normal epithelium 3.
Patients with Peutz-Jeghers syndrome have an increased prevalence of adenomas within the gallbladder.
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.
Overall size is probably the most useful indicator of malignancy, with polyps over 10 mm in diameter having a reported malignancy rate of 37-88% 3.
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 gallbladder lumen, which is usually immobile unless there is a relatively long pedunculated component.
Features of a cholesterol polyp include 8:
- small size
- over 90% are <10 mm, the vast majority less than <5 mm
- 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
Adenomas, on the other hand, tend to be larger, solitary, more often sessile with internal vascularity, and of intermediate echogenicity. It is impossible to confidently distinguish an adenoma from an adenocarcinoma 6-8.
Rarely, endoscopic ultrasound may be useful to further assess gallbladder polyps as it may generate higher resolution images 7-8.
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
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 actually progress to cancer 10.
Recommended follow-up of small polyps (<10 mm) varies from author to author. A commonly accepted strategy includes:
- ≤6 mm: no further follow up necessary 6,10
- 6-9 mm: follow up to ensure no interval growth; follow-up interval varies from 3 to 6 months 6,9
- ≥10 mm: surgical consultation
- usually warrants cholecystectomy
- if no cholecystectomy, annual follow up is justified 11
Lower thresholds for follow up or intervention may be warranted if one's 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:
- 1. Kwon W, Jang JY, Lee SE et-al. Clinicopathologic features of polypoid lesions of the gallbladder and risk factors of gallbladder cancer. J. Korean Med. Sci. 2009;24 (3): 481-7. doi:10.3346/jkms.2009.24.3.481 - Free text at pubmed - Pubmed citation
- 2. Lee KF, Wong J, Li JC et-al. Polypoid lesions of the gallbladder. Am. J. Surg. 2004;188 (2): 186-90. doi:10.1016/j.amjsurg.2003.11.043 - Pubmed citation
- 3. Levy AD, Murakata LA, Abbott RM et-al. From the archives of the AFIP. Benign tumors and tumorlike lesions of the gallbladder and extrahepatic bile ducts: radiologic-pathologic correlation. Armed Forces Institute of Pathology. Radiographics. 22 (2): 387-413. Radiographics (full text) - Pubmed citation
- 4. Aldridge MC, Bismuth H. Gallbladder cancer: the polyp-cancer sequence. Br J Surg. 1990;77 (4): 363-4. Pubmed citation
- 5. Lane J, Buck JL, Zeman RK. Primary carcinoma of the gallbladder: a pictorial essay. Radiographics. 1989;9 (2): 209-28. Radiographics (abstract) - Pubmed citation
- 6. Harisinghani MG, Mueller PR. Teaching Atlas of Abdominal Imaging. Thieme. (2009) ISBN:1588906566. Read it at Google Books - Find it at Amazon
- 7. Sugiyama M, Atomi Y, Kuroda A et-al. Large cholesterol polyps of the gallbladder: diagnosis by means of US and endoscopic US. Radiology. 1995;196 (2): 493-7. Radiology (abstract) - Pubmed citation
- 8. Skucas J. Advanced imaging of the abdomen. Springer Verlag. (2006) ISBN:1852339926. Read it at Google Books - Find it at Amazon
- 9. Andrén-Sandberg A. Diagnosis and management of gallbladder polyps. N Am J Med Sci. 2012;4 (5): 203-11. N Am J Med Sci (full text) - doi:10.4103/1947-2714.95897 - Free text at pubmed - Pubmed citation
- 10. Corwin MT, Siewert B, Sheiman RG et-al. Incidentally detected gallbladder polyps: is follow-up necessary?-Long-term clinical and US analysis of 346 patients. Radiology. 2011;258 (1): 277-82. Radiology (full text) - doi:10.1148/radiol.10100273 - Pubmed citation
- 11. Sebastian S, Araujo C, Neitlich JD et-al. Managing incidental findings on abdominal and pelvic CT and MRI, Part 4: white paper of the ACR Incidental Findings Committee II on gallbladder and biliary findings. J Am Coll Radiol. 2013;10 (12): 953-6. doi:10.1016/j.jacr.2013.05.022 - Pubmed citation
- 12. Mellnick VM, Menias CO, Sandrasegaran K et-al. Polypoid lesions of the gallbladder: disease spectrum with pathologic correlation. Radiographics. 2015;35 (2): 387-99. doi:10.1148/rg.352140095 - Pubmed citation
Ultrasound - gallbladder
- ultrasound (introduction)
- gallbladder ultrasound
- diffuse gallbladder wall thickening (differential)
- focal gallbladder wall thickening (differential)
- gallbladder sludge
- acute cholecystitis
- chronic cholecystitis
- gallbladder polyp
- porcelain gallbladder
- gallbladder carcinoma
- gallbladder metastases
- gallbladder lymphoma
- gallbladder volvulus / torsion
- variants and anomalies