What is the appropriate workup for a patient presenting with a gallbladder polyp, considering factors such as polyp size, patient age, and symptoms?

Workup of Gallbladder Polyps

Begin with optimized transabdominal ultrasound as the primary diagnostic modality, using high-frequency probes, color Doppler, and proper fasting preparation to characterize polyp size, morphology, vascularity, and any concerning features. 1, 2

Initial Ultrasound Assessment

The first step is obtaining a high-quality ultrasound with specific attention to:

• Polyp size measurement (maximum diameter in millimeters) 1, 2
• Morphology: Distinguish pedunculated "ball-on-the-wall" appearance (thin stalk attachment) from sessile (broad-based) morphology 1, 2
• Vascularity: Use color Doppler to confirm internal blood flow, which differentiates true polyps from tumefactive sludge 1, 2
• Focal wall thickening: Measure adjacent gallbladder wall thickness, with ≥4 mm being a concerning feature 2, 3
• Multiplicity: Document whether polyp is solitary or multiple 4
• Mobility: Confirm the lesion is fixed and non-mobile (true polyps) versus mobile and layering (tumefactive sludge) 2, 5

Patient preparation is critical—ensure 4-6 hours of fasting to optimize gallbladder distension and minimize sludge artifacts. 1

Risk Stratification Based on Size and Morphology

Polyps ≥15 mm

Refer immediately for surgical consultation regardless of other features, as these have the highest malignancy risk. 1, 2 Neoplastic polyps average 18.1-18.5 mm compared to 7.5-12.6 mm for nonneoplastic polyps. 2

Polyps 10-14 mm

Consider surgical consultation, with decision-making based on patient risk factors and morphology. 1, 2 If surveillance is chosen over immediate surgery, perform follow-up ultrasound at 6,12, and 24 months. 1, 2

Polyps 6-9 mm

Assess for risk factors that warrant either cholecystectomy or surveillance:

• Age >60 years 3
• Primary sclerosing cholangitis (PSC) 1, 3
• Asian ethnicity 5, 3
• Sessile morphology 2, 3
• Focal wall thickening >4 mm 2, 3

If risk factors present: Consider cholecystectomy or surveillance at 6 months, 1 year, and 2 years. 3

If no risk factors: Surveillance at 6 months, 1 year, and 2 years. 3

Polyps ≤5 mm

No follow-up required if no risk factors present, as malignancy risk is virtually zero. 2, 5, 3 In large series involving approximately 3 million gallbladder ultrasounds, no documented cases of malignancy occurred in polyps <10 mm at initial detection. 1

Pedunculated "Ball-on-the-Wall" Polyps ≤9 mm

No follow-up required regardless of other factors, as these have extremely low malignancy risk. 1, 2

Advanced Imaging for Problem Cases

When initial ultrasound cannot differentiate between true polyp, tumefactive sludge, or adenomyomatosis in polyps ≥10 mm:

First-Line Advanced Imaging: Contrast-Enhanced Ultrasound (CEUS)

CEUS is the preferred next step when available, as it provides superior characterization compared to CT or MRI. 1, 2, 6

CEUS enhancement patterns:

• Non-neoplastic lesions: Late hypoenhancement compared to liver 1, 6
• Neoplastic lesions: Marked early enhancement 1, 6
• Cholesterol polyps: Stalk-like central enhancement 1
• Adenomatous polyps: Eccentric hyperenhancement with intralesional straight vessels 1
• Malignant polyps: Wash-out pattern with intralesional branching vessels 1
• Tumefactive sludge: No internal enhancement (avascular) 1, 6

Alternative: MRI

Use MRI if CEUS unavailable, though diagnostic accuracy is inferior to CEUS for this purpose. 1, 6

MRI characteristics:

• High T1 signal: Suggests cholesterol polyps or pigment stones 1, 6
• Restricted diffusion: Suggestive of malignancy 1, 6
• Intermediate-high T2 signal: More suspicious finding 1
• Rokitansky-Aschoff sinuses: Definitively diagnoses adenomyomatosis 1, 6

Role of CT

CT has inferior diagnostic accuracy compared to CEUS or MRI for gallbladder polyp characterization. 1 However, findings suggesting malignancy include size >15 mm, sessile shape, and visibility on unenhanced CT. 1

Endoscopic Ultrasound (EUS)

EUS data are conflicting and not routinely recommended. 1 Consider only in select cases where other modalities are inconclusive, though it requires specialized expertise. 3, 7

Surveillance Protocol and Growth Criteria

Surveillance Intervals

For polyps requiring follow-up: Ultrasound at 6 months, 1 year, and 2 years. 1, 2, 3

Discontinue surveillance after 2-3 years if stable, as extended follow-up is not productive. 1, 2 In one large study, 68% of gallbladder cancers associated with polyps were detected within the first year, and after 4 years, only one cancer was found in 137,633 person-years of follow-up. 1

Growth Triggers for Surgical Referral

Growth of ≥4 mm within 12 months constitutes rapid growth and warrants immediate surgical consultation, regardless of absolute polyp size. 1, 2 This threshold is based on anecdotal reports of polyps growing from 7 to 16 mm over 6 months developing into malignancy. 1

Growth to ≥10 mm at any point during surveillance mandates surgical consultation. 2, 3

Natural History Considerations

Growth of 2-3 mm is part of the natural history of nonmalignant polyps and should not trigger intervention. 1, 2, 5 Almost half of polyps increase or decrease in size naturally, and up to 34% may resolve completely. 1, 2

Special Population: Primary Sclerosing Cholangitis

PSC patients require a dramatically lower threshold for intervention, with malignancy risk of 18-50% in gallbladder polyps. 2

Cholecystectomy is recommended for polyps ≥8 mm in PSC patients (compared to ≥10 mm in general population). 1, 2 Smaller polyps should be characterized with CEUS, and if contrast-enhancing, cholecystectomy should be considered regardless of size. 1

For non-contrast-enhancing polyps <8 mm: Follow-up ultrasound at 3-6 months. 1

Critical Pitfalls to Avoid

Do not confuse tumefactive sludge with true polyps: Sludge is mobile, layering, and avascular on Doppler, while true polyps are fixed, non-mobile, non-shadowing, and demonstrate internal vascularity. 2, 5

Do not over-surveil small polyps: 60% of gallbladder polyps are benign cholesterol polyps with negligible malignancy risk. 2 Polyps ≤5 mm without risk factors require no follow-up whatsoever. 5, 3

Recognize frank invasion immediately: If ultrasound shows direct liver invasion, liver metastases, or focal wall thickening ≥4 mm with concerning features, bypass the standard algorithm and refer immediately to an oncologic specialist. 1, 6

Do not perform percutaneous biopsy: This is contraindicated due to risk of tumor seeding if malignancy is present and curative resection or transplantation is being considered. 1

Adenomyomatosis mimics polyps: Look for comet-tail artifact on gray-scale imaging or twinkling artifact on color Doppler from intramural cholesterol crystals, and Rokitansky-Aschoff sinuses appearing as intramural cysts. 6