Gallbladder polyps are elevated lesions on the mucosal surface of the gallbladder. The vast majority are benign, but malignant entities are possible. Gallbladder polyps may be detected on ultrasound, CT, or MRI, but are usually best characterized on ultrasound.
Gallbladder polyps are relatively frequent, seen in up to 5% of the population 1,7. 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, during imaging for upper abdominal discomfort. In most instances, however, the polyps themselves are thought to be 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. Histologically, they are composed of lipid-laden macrophages, covered with 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 10mm in diameter having a 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 cholesterol polyp include 8:
- small size
- over 90% are <10 mm, the vast majority less than <5 mm
- echogenicity varies with 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 not possible to 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 bladder, 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:
- <5 mm: no further follow up necessary 6,10
- 5-10 mm: follow-up to ensure no interval growth. Follow-up interval varies from 3 to 6 months 6,9.
- >10 mm: usually warrant cholecystectomy.
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, or females in India).
The differential for a gallbladder polyp is limited, and includes 6:
- usually mobile, but may be adherent
- usually casts an acoustic shadow
- biliary sludge
- gallbladder carcinoma
- ultrasound (introduction)
- ultrasound physics
- basic physics
- pulse-echo imaging
- real-time imaging
- contrast-enhanced ultrasound
- Doppler imaging
- ultrasound artifacts
- biological effects of ultrasound
- history of ultrasound
- obstetric ultrasound
- first trimester
- ectopic pregnancy
- second trimester
- gynaecologic ultrasound
- peritoneal inclusion cyst
- vascular ultrasound
- breast ultrasound
- shoulder ultrasound
- elbow ultrasound
- wrist ultrasound
- hand ultrasound
- hip ultrasound
- knee ultrasound
- ankle/foot ultrasound
- paediatric musculoskeletal ultrasound
- skin/soft tissue ultrasound
- ultrasound of arthropathies
- liver ultrasound
- hepatic vasculature
- hepatic trauma on ultrasound
- liver transplant
- gallbladder ultrasound
- pancreas ultrasound
- pancreatic carcinoma
- pancreatic endocrine tumors / islet cell tumors
- cystic pancreatic neoplasms
- pancreas transplant
- gastrointestinal ultrasound
- renal ultrasound
- renal stone
- focal lesion
- renal vascular
- renal transplant ultrasound
- bladder ultrasound
- scrotal/testicular ultrasound
- unilateral testicular lesion
- bilateral testicular lesion
- cyst of the tunica albuginea
- tubular ectasia of the rete testis
- testicular lymphoma
- prostate carcinoma
- other lower genitourinary
- neck and thyroid ultrasound
- pediatric ultrasound
- ultrasound interventions
- ultrasound guided biopsy
- ultrasound guided percutaneous drainage
- ultrasound guided musculoskeletal interventions
- joint injection
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- 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
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Cholesterol polyp of the gallbladder||✓|
|Polyp of gallbladder||✗|