Gallbladder Polyps

Published on 19/07/2015 by admin

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Last modified 22/04/2025

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 Large polyps may show internal color flow vascularity

image “Comet tail” artifacts suggest cholesterol polyp
• CT: Useful for staging in larger polyps where ↑ risk of malignancy

image Difficult to visualize many polyps on CT due to lower spatial resolution
image Can show variable enhancement; no convincing correlation between enhancement and malignancy
image Useful for staging in larger polyps where ↑ risk of malignancy

TOP DIFFERENTIAL DIAGNOSES

• Tumefactive sludge
• Gallstone
• Polypoid GB carcinoma
• GB metastases
• Adenomyomatosis

PATHOLOGY

• Classification

image Neoplastic: Adenoma, adenoma-carcinoma, miscellaneous (fibroma, lipoma, etc.)
image Nonneoplastic: Cholesterol polyp, adenomyoma, inflammatory polyp, choristoma

CLINICAL ISSUES

• Size is most important predictor of malignancy

image 100% of polyps > 20 mm are malignant
image 43-77% of polyps 10-20 mm are malignant
image 94% of benign polyps are < 10 mm
• Risk factors for malignancy: Age > 60, gallstones, coexistence of primary sclerosing cholangitis (PSC)
• Reassuring factors: Stability over time, multiple polyps, pedunculated (versus sessile) morphology
• Current recommendations

image Cholecystectomy if patient is symptomatic or has cholelithiasis or PSC (regardless of polyp size)
image Polyp > 18-20 mm: Open cholecystectomy
image Polyp 10-20 mm: Laparoscopic cholecystectomy
image Polyp 6-9 mm: Serial follow-up at 3, 6, and 12 months
image Polyp ≤ 5 mm: Serial imaging (no consensus; malignancy is extremely rare and some advocate no follow-up)
image
(Left) Ultrasound of a 43-year-old woman with right upper quadrant pain shows mild gallbladder (GB) wall thickening and multiple small (< 5 mm), slightly echogenic polyps image. An elective laparoscopic cholecystectomy for presumed biliary colic revealed cholesterolosis and cholesterol polyps.

image
(Right) Ultrasound image shows multiple polyps image in the GB that measure < 1 cm in size. While the data suggests nodules < 1 cm harbor a very low risk of malignancy, most society guidelines suggest imaging follow-up.
image
(Left) Ultrasound of a 41-year-old man with chest pain shows two 4-mm GB polyps image. Their small size, echogenicity, multiplicity, and stability at follow-up sonography indicate hyperplastic (cholesterol) polyps.

image
(Right) Ultrasound of a 47-year-old woman shows a 1-cm, pathologically confirmed adenomatous polyp image. The likelihood of neoplasia increases with polyp size, but most GB polyps are hyperplastic.

TERMINOLOGY

Definitions

• Polypoid or sessile mass protruding from gallbladder (GB) mucosa

IMAGING

General Features

• Best diagnostic clue

image Nonmobile hyperechoic mass protruding from GB mucosa without acoustic shadowing
• Location

image GB lumen
• Morphology

image Sessile or pedunculated

Imaging Recommendations

• Best imaging tool

image Ultrasound; endoscopic ultrasound (EUS)
• Protocol advice

image Grayscale and color Doppler US with 6 MHz transducer

CT Findings

• Often difficult to visualize on CT due to lower spatial resolution

image CT underestimates polyp size compared to US
• Best visualized on CECT due to vascularity of polyp

image Can show variable enhancement
image No convincing evidence that polyp enhancement pattern predicts malignancy
• Ill-defined margins of larger polyps possible predictor of malignancy
• Useful for local staging (including lymph node metastases, liver invasion, metastases) in larger polyps where risk of malignancy is high

Ultrasonographic Findings

• Ultrasound is insensitive (only 50%) for polyps, detecting only 1/2 of polyps found at histopathology
• False-positive rate of up to 30%, with positive predictive value of only 10% (compared to histopathology)

image Poor accuracy rates for polyps < 5 mm
image Potentially due to stones, GB folds, sludge, or cholesterolosis mimicking polyps
image Roughly 10% of polyps disappear on follow-up ultrasounds

– Original polyp may have been spurious, but could also reflect polyps breaking off or resolution of inflammatory polyps
• Immobile echogenic mucosal excrescence/nodule, either sessile or lobulated

image No acoustic shadowing, unlike stones
image Highly echogenic foci or “comet tail” artifacts within polyp suggests a cholesterol polyp
image Large polyps may show internal vascularity on color Doppler US
image No clear sonographic features to differentiate benign and malignant polyps

– Questionable link between sessile morphology and malignancy
– Multiple nodules more likely to be benign (usually cholesterol polyps); neoplastic polyps often solitary
• EUS has been shown to have higher accuracy in differentiation of benign (97%) vs. malignant (76%) polyps

image Better demonstration of mucosal invasion

Nuclear Medicine Findings

• PET/CT

image GB carcinoma has avid FDG uptake (relative to liver)
image Some studies suggest role of PET in malignancy risk stratification of polyps 10-20 mm

DIFFERENTIAL DIAGNOSIS

Tumefactive Sludge

• Focal collection of sludge (cholesterol or calcium bilirubinate crystals) appearing polypoid or mass-like
• No acoustic shadowing or internal flow on color Doppler imaging
• Sludge will slowly move when altering patient position during scanning

Gallstone

• Posterior acoustic shadowing
• “Twinkling” artifact with color Doppler US
• Freely mobile within GB unless impacted

Polypoid GB Carcinoma

• Typically larger than adenoma, most often > 15 mm
• May cause focal loss of wall reflectivity due to mural invasion
• Internal flow often detectable with color Doppler US
• Porta hepatis adenopathy &/or direct liver invasion
• Often associated with stones

GB Metastases

• Melanoma most common
• Enhancing polypoid mass in setting of widespread metastatic disease

Adenomyomatosis

• Can be nodular and mass-like, but usually associated with “comet-tail” artifact

PATHOLOGY

General Features

• Etiology

image Unknown
• Genetics

image GB adenomas associated with familial adenomatous polyposis and Peutz-Jeghers syndrome

Staging, Grading, & Classification

• Neoplastic polyps

image Adenoma

– Benign
– Accounts for 0.5-4% of polyps
– Solitary, usually in range of 5-20 mm
– Often associated with gallstones
– Progression to adenocarcinoma is yet unclear; adenoma-carcinoma sequence seen in colon cancer has not been defined for GB

image Not clear that GB cancers arise from adenomas
image Adenocarcinoma

– 15-25% of GB adenocarcinomas present as polypoid lesions
– Solitary, usually > 1 cm (in 1 study 88% were > 1 cm)
– May have thickened implantation base or evidence of mucosal invasion
image Rare benign lesions: Leiomyoma, lipoma, neurofibroma, carcinoid
image Rare malignant lesions: Squamous cell carcinoma, mucinous cystadenocarcinoma
• Nonneoplastic polyps

image Majority (> 95%) of cases
image Cholesterol polyps

– 1/3 of cases in cholesterolosis are polypoid, the rest manifest as diffuse nodularity of GB
– Accounts for 60% of all polyps
– Infiltration of mucosa and lamina propria with lipid-laden foamy macrophages
– Multiple, < 10 mm
image Adenomyomatosis

– Localized (focal) adenomyomatosis can mimic polyps
– Accounts for 25% of polyps
– Usually seen in fundus, usually 10-20 mm
– Excessive epithelial proliferation with invagination into muscular layer
image Inflammatory polyps

– Accounts for 10% of polyps
– Result from granulation and fibrous tissue secondary to chronic inflammation
– Sessile or pedunculated, usually < 10 mm
image Choristoma (rare): Heterotopic gastric, pancreatic, or hepatic tissue

Microscopic Features

• Adenomas may be tubular, papillary, or tubulopapillary

image Tubular adenoma most common variant

– Covered with biliary epithelium, composed of pyloric or intestinal-type glands
image Papillary adenomas

– Papillary structures lined by cuboidal or columnar cells
image Tubulopapillary adenomas are composite of both
• Cholesterol polyp composed of sheets of lipid-laden macrophages with normal overlying GB mucosa

CLINICAL ISSUES

Presentation

• Most common signs/symptoms

image Most are asymptomatic
• Other signs/symptoms

image Debatable association with chronic dyspepsia
image Cholesterol polyps can detach and behave like stones

– Can cause biliary colic, obstruction, pancreatitis
image Lab markers: CEA and CA19-9 have no role in differentiating benign and malignant polyps

Demographics

• Epidemiology

image Prevalence varies by demographics of studied population

– 1.5-5% in abdominal ultrasounds
– 0.005-13.8% of resected GBs
image No consistent relationship with age, gender, or obesity
image 1 study showed inverse relationship with stones

– May be harder to diagnose polyps in presence of cholelithiasis

Natural History & Prognosis

• Natural history and management of polyps has been an area of great debate, with no management consensus
• Large prospective study of incidental polyps < 10 mm showed no change in size in 2- and 5-year follow-ups
• Retrospective study of 346 incidental polyps demonstrated growth in only 1% of cases; no lesions < 6 mm were neoplastic
• Risk factors for malignancy

image Proposed risk factors for malignancy include: Age > 60 years, gallstone, coexistence of primary sclerosing cholangitis (PSC), and irregular GB wall thickening or sessile morphology of polyp on US

– Other concerning features: Irregular GB wall thickening and sessile morphology of polyp
image Size is most useful predictor of malignancy

– 100% of polyps > 20 mm are malignant (either invasive carcinoma or high-grade dysplasia)
– 43-77% of polyps 10-20 mm are malignant
– 94% of benign polyps are < 10 mm; 88% of malignant polyps are > 10 mm
– Although older studies suggested a cut-off value of 10 mm for safely differentiating benign from malignant polyps, some studies propose changing cut-off to 6 mm for reaching 100% sensitivity (albeit in cost of lower specificity)
image Reassuring factors: Stability over time, multiple polyps, pedunculated (versus sessile)

Treatment

• No consensus exists regarding management of polyps

image Recommendations vary among different specialty societies
• Current recommendations

image Cholecystectomy if patient is symptomatic or if there is coexisting gallstone or PSC (regardless of size of polyp)
image Polyp > 18-20 mm: CT, PET, &/or EUS for preoperative staging → open cholecystectomy with possible resection of adjacent liver tissue
image Polyp 10-20 mm: Cholecystectomy
image Polyp 6-9 mm: Serial follow-up imaging in 3, 6, and 12 months (no consensus on frequency of follow-up)
image Polyp ≤ 5 mm: Serial imaging (no consensus; malignancy is extremely rare in this group and some recommend no follow-up)

DIAGNOSTIC CHECKLIST

Consider

• Size is most important predictor of malignancy
• Although risk of malignancy in small (< 6 mm) polyps is extremely low, some guidelines still recommend surveillance ultrasound
image
(Left) Ultrasound of a 43-year-old man shows 2 tiny GB polyps image. Assessment of mobility during real-time examination helps to differentiate between polyps and small, nonshadowing stones or sludge.

image
(Right) Axial T2WI FS MR of the same patient shows two GB polyps image. These incidental polyps were stable 2 years later. Although tiny polyps are rarely malignant, ultrasound surveillance is typically advocated. How long and at what interval these small polyps should be followed is controversial.
image
(Left) Ultrasound of a 55-year-old woman shows a 1.8 cm polyp image within the GB fundus. Loss of reflectivity of the adjacent GB wall image might suggest a neoplastic polyp. This and the size of the polyp prompted elective cholecystectomy, which revealed a solitary but large cholesterol polyp.

image
(Right) Axial CECT of the same patient shows an enhancing, nondependent lesion image within the GB fundus. The lack of transmural invasion at CT prompted a laparoscopic, rather than open, cholecystectomy.
image
(Left) Ultrasound of a 55-year-old woman with right upper quadrant pain shows a > 2 cm sessile polypoid GB lesion image. Laparoscopic cholecystectomy was performed because of the patient’s symptoms and the size/configuration of the polyp.

image
(Right) Axial CECT of the same patient shows focal thickening of the GB wall image and no obvious transmural disease. An invasive GB adenocarcinoma was identified at pathology. Early stage, incidental GB carcinoma often appears as a sessile polyp at imaging.
image
Longitudinal grayscale ultrasound in a 42-year-old man presenting for routine screening for hepatitis B demonstrates small GB polyps image on both the anterior and posterior walls of the GB, most consistent with cholesterol polyps.

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