Gallbladder adenoma is a benign neoplastic polyp arising from gallbladder epithelium, constituting 4-7% of all gallbladder polyps. Adenomas contain dysplastic epithelial proliferation and may follow the adenoma-carcinoma sequence — the only true neoplastic polyp type carrying malignancy potential. On US, it usually appears as a solitary, sessile or pedunculated, echogenic intraluminal polypoid lesion. Size is the most critical risk factor: malignancy risk reaches 37-53% in adenomas >10 mm, indicating cholecystectomy. Polyps <10 mm are followed with US at 6-12 month intervals. Distinction from cholesterol polyps (60-90% of gallbladder polyps) is clinically critical — cholesterol polyps are usually multiple, small (<10 mm), and broad-based, while adenomas are usually solitary and larger. Contrast-enhanced US (CEUS) and contrast-enhanced MRI help in adenoma-cholesterol polyp differentiation — adenomas show early arterial enhancement. Histologically, tubular, papillary, and tubulopapillary subtypes are defined; the papillary form has the highest dysplasia potential.
Age Range
35-75
Peak Age
55
Gender
Equal
Prevalence
Rare
Gallbladder adenoma originates from clonal neoplastic proliferation in the gallbladder mucosal epithelium. The normal mucosal epithelium → dysplastic adenoma → carcinoma sequence (adenoma-carcinoma sequence) has been described similarly to colorectal cancer, but this process may be faster in the gallbladder. In adenoma, epithelial cells show dysregulated growth pattern — nuclear atypia, increased mitotic activity, and glandular architecture disruption. This neoplastic proliferation forms an intraluminal polypoid mass — may be pedunculated (stalked) or sessile (broad-based). Pedunculated adenomas contain a vascular pedicle and are characterized by stalk mobility on US. As the adenoma grows, dysplasia grade increases → high-grade dysplasia → in-situ carcinoma → invasive carcinoma may develop. Size-dysplasia correlation is strong: low-grade dysplasia predominates in adenomas <10 mm, while high-grade dysplasia and focal carcinoma risk reaches 37-53% in adenomas >10 mm. The vascular structure of adenoma contains neoplastic neovascularization — this feature is reflected as early arterial enhancement on contrast imaging and allows distinction from cholesterol polyps (avascular or minimally vascular). Cholesterol polyps form from accumulation of lipid-laden macrophages beneath the mucosa — not true neoplasia and carry no malignancy risk.
Solitary, immobile, >10 mm polypoid lesion on US + internal vascularity on Doppler/CEUS — the strongest imaging finding combination for neoplastic polyp carrying adenoma-carcinoma sequence risk. The >10 mm threshold is the cholecystectomy decision point.
On B-mode US, a solitary, isoechoic-hyperechoic polypoid lesion arising from the wall is seen in the gallbladder lumen. The lesion does not move with positional change (distinction from stone and sludge) and does not create posterior acoustic shadow (distinction from stone). In pedunculated form, a thin stalk (pedicle) is recognizable and may show slight mobility on real-time US. In sessile form, the lesion is attached to the wall with a broad base — broad base is more concerning for malignancy risk. Size measurement is critical: >10 mm indicates cholecystectomy. Accompanying gallstones (cholelithiasis) may be present — stones create posterior shadow and are mobile. Wall thickening or focal irregularity raises malignant transformation suspicion.
Report Sentence
A __ mm solitary, immobile polypoid lesion is seen in the gallbladder fundus; considering the size, it suggests adenoma/neoplastic polyp.
On color/power Doppler, arterial vascularity is seen within the adenoma lesion or its stalk — low-moderate resistance arterial flow is detected (RI 0.5-0.7). In pedunculated adenomas, the feeding artery within the stalk can be identified. This vascularity finding is valuable in distinguishing adenoma from cholesterol polyps — cholesterol polyps are avascular or minimally vascular with no Doppler signal. However, in small adenomas (<6 mm), Doppler sensitivity may be limited due to low flow velocities — power Doppler is more sensitive than color Doppler. In malignant transformation, vascularity increases and becomes irregular — very low resistance flow (RI <0.4) raises malignancy suspicion.
Report Sentence
Internal arterial flow is demonstrated within the polyp lesion on Doppler (RI: __); vascularized polyp — consistent with adenoma.
On contrast-enhanced ultrasound (CEUS), adenoma shows rapid and homogeneous enhancement in the early arterial phase (10-20 seconds after contrast injection) — the lesion enhances earlier and more intensely than the surrounding gallbladder wall. Enhancement is preserved in portal and late phases (no wash-out — benign feature). Cholesterol polyps show no enhancement or only mild late-phase enhancement on CEUS. Malignant lesions (adenocarcinoma) show early intense enhancement with conspicuous late-phase wash-out. CEUS can differentiate benign/malignant with 85-95% accuracy in gallbladder polyps and reduces unnecessary cholecystectomies.
Report Sentence
Rapid, homogeneous enhancement is seen in the polyp lesion in the early arterial phase on CEUS with no late-phase wash-out; consistent with vascularized benign polyp (adenoma).
On T2-weighted MRI, the adenoma is seen as a polypoid lesion with intermediate signal within bile (hyperintense). The adenoma stands out with intermediate signal against the markedly T2-hyperintense bile background. Reliable distinction from cholesterol polyps by T2 signal is not possible — both may show similar T2 signal. Contrast-enhanced T1 sequences are more useful for differentiation: adenoma shows early arterial enhancement, cholesterol polyp does not. DWI has limited value in small polyps but low ADC in large lesions raises malignancy suspicion.
Report Sentence
A __ mm polypoid lesion showing intermediate signal against the bile background on T2 is seen in the gallbladder lumen.
On gadolinium-enhanced dynamic MRI, adenoma shows early, homogeneous enhancement in the arterial phase (20-30 seconds after contrast injection). Enhancement is more conspicuous than the gallbladder wall. Enhancement is preserved in portal venous and delayed phases — no wash-out as in malignant lesions. Cholesterol polyps show no or minimal arterial phase enhancement. This enhancement pattern reflects the neoplastic neovascularization of adenoma and yields results parallel to CEUS findings. Dynamic contrast-enhanced MRI can influence management decisions for 8-10 mm polyps — cholecystectomy is recommended in the presence of early enhancement.
Report Sentence
Early, homogeneous enhancement is seen in the gallbladder polyp in the arterial phase with no late-phase wash-out; consistent with vascularized benign polyp (adenoma).
On contrast-enhanced CT, an enhancing polypoid lesion may be seen in the gallbladder lumen — however, CT has lower sensitivity than US and MRI for gallbladder polyp evaluation (especially polyps <10 mm). The polyp appears as an intraluminal structure denser than bile (0-20 HU), enhancing at 40-80 HU. The main value of CT in large polyps (>10 mm) is wall invasion, pericholecystic infiltration, and lymph node assessment — used for staging when malignancy is suspected. Irregular gallbladder wall thickening or invasion into adjacent liver parenchyma suggests malignant transformation.
Report Sentence
A __ mm enhancing polypoid lesion is seen in the gallbladder lumen; no wall irregularity or pericholecystic infiltration identified.
Criteria
Adenoma type showing tubular pattern of neoplastic glandular structures. Most common subtype. Dysplasia grade usually low-moderate. Malignancy risk lower than papillary type but increases with size.
Distinct Features
Homogeneous, smooth-surfaced polyp on US. Enhancement pattern is homogeneous and regular. Regular glandular structure preserved.
Criteria
Adenoma type showing papillary (villous) growth pattern of neoplastic epithelial cells. Subtype with highest dysplasia and malignancy potential. High-grade dysplasia rate significantly higher than tubular type.
Distinct Features
May have irregular or lobulated surface on US — papillary projections recognizable. More heterogeneous enhancement. Size usually larger than tubular type. Cholecystectomy may be recommended even <10 mm.
Criteria
Mixed adenoma type containing both tubular and papillary components. Dysplasia risk depends on component ratio — risk increases as papillary component increases.
Distinct Features
Partially regular, partially irregular surface on US. Enhancement may be heterogeneous — papillary areas enhance more intensely. Size and dysplasia correlation intermediate between tubular and papillary.
Distinguishing Feature
Cholesterol polyps are usually multiple (<5), small (<10 mm), broad-based, and brightly hyperechoic. Show no vascularity on Doppler, no enhancement on CEUS. Adenoma is usually solitary, larger, showing vascularization on Doppler/CEUS. Cholesterol polyps have no malignancy risk.
Distinguishing Feature
Gallbladder carcinoma is usually an irregular mass >20 mm showing wall invasion, pericholecystic infiltration, and regional lymphadenopathy. Early enhancement + conspicuous late wash-out on CEUS. Adenoma is smooth-margined without wall invasion or wash-out. However, focal carcinoma may be found in adenomas >10 mm — histological distinction may be needed.
Distinguishing Feature
Adenomyomatosis shows focal wall thickening and intramural diverticula (Rokitansky-Aschoff sinuses) — 'comet-tail' artifact is characteristic on US. Adenoma is an intraluminal polypoid mass without comet-tail artifact. Adenomyomatosis is a wall disease, adenoma is a luminal disease.
Distinguishing Feature
Sludge ball (tumefactive sludge) shifts with positional change (mobile), may show posterior acoustic enhancement, and has no vascularity on Doppler. Adenoma is immobile (does not separate from wall), shows vascularity on Doppler. Sludge ball shows no enhancement on CEUS.
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
6-monthManagement strategy for gallbladder adenomas is size-based. Cholecystectomy is indicated for polyps >10 mm — due to adenoma-carcinoma sequence risk. For 6-9 mm polyps, risk factors are assessed: solitary lesion, sessile morphology, vascularization on CEUS/MRI, age >50, PSC, Indian ethnicity — cholecystectomy considered if present; otherwise 6-month US follow-up. For <6 mm polyps, 12-month US follow-up is sufficient — re-evaluated if growth or morphology change occurs. Percutaneous biopsy is not performed for gallbladder polyps — peritoneal bile leakage and tumor seeding risk. Laparoscopic cholecystectomy is the standard surgical approach. Intraoperative frozen section is recommended for polyps >10 mm to assess need for extended resection. CEUS and contrast-enhanced MRI play an increasingly important role in polyp characterization — reducing unnecessary cholecystectomy rates.
Gallbladder adenoma is a premalignant lesion (adenoma-carcinoma sequence). Polyps >10 mm are an indication for cholecystectomy. Size increase raises the risk of dysplasia/carcinoma. If growth is demonstrated on follow-up, surgery should be planned.