I have a 7‑cm gallbladder polyp on endoscopic ultrasound that measured 5 cm on a conventional ultrasound 7 months later; why is there a size discrepancy and should I have annual ultrasound surveillance?

Understanding the Size Discrepancy Between EUS and Ultrasound

The apparent "shrinkage" from 7 cm to 5 cm is almost certainly measurement variability between imaging modalities rather than true polyp regression, and you absolutely need immediate surgical consultation—not annual surveillance—because any gallbladder polyp measuring 5-7 cm has extremely high malignancy risk.

Why the Size Discrepancy Occurred

Measurement variability between imaging modalities is substantial and well-documented. The size difference you're seeing reflects technical and observer-related factors rather than actual polyp behavior:

• Inter-modality measurement errors routinely span 2-4 mm or more, with 95% limits of agreement between different imaging techniques and observers ranging approximately ±4 mm for polyp measurements 1
• EUS and conventional ultrasound measure structures differently due to differences in probe frequency, image resolution, measurement planes, and the specific location where measurements are obtained 1
• Observer variability compounds the problem, as different radiologists or sonographers measuring the same lesion can report sizes differing by several millimeters, with measurement errors propagating when comparing studies over time 1
• The 95% limits of agreement for repeated measurements can span ranges of 40-60%, meaning substantial size variation is expected even when measuring the same structure 1

Your Immediate Management Priority

You need urgent surgical consultation, not surveillance imaging. Here's why:

• Any gallbladder polyp ≥15 mm requires immediate surgical consultation because size ≥15 mm is an independent risk factor for neoplastic lesions with markedly elevated malignancy risk 2
• Even using the smaller 5 cm measurement, your polyp is 50 mm—more than three times the surgical threshold 2, 3
• The cancer detection rate for polyps ≥20 mm is 94.1%, meaning your lesion has an extremely high probability of malignancy regardless of which measurement is accurate 4
• Neoplastic polyps average 18.1-18.5 mm compared to 7.5-12.6 mm for benign polyps, and your lesion far exceeds even the neoplastic average 2

Why Annual Surveillance Is Inappropriate

Surveillance protocols apply only to small polyps with low malignancy risk, not large lesions like yours:

• Surveillance is recommended only for polyps 6-9 mm with risk factors or polyps <6 mm in specific circumstances—your polyp is 8-10 times larger than the surveillance threshold 2, 3
• The surveillance algorithm explicitly states that polyps ≥10 mm require surgical referral, not imaging follow-up 3
• Extended surveillance beyond 2-3 years is unproductive even for small polyps, as 68% of gallbladder cancers associated with polyps are detected within the first year 2
• Annual ultrasound would be dangerous delay given the extremely high malignancy probability at this size 2, 4

Critical Next Steps

Immediate actions required:

• Contact your surgeon or gastroenterologist within days to discuss cholecystectomy, as any delay with a 5-7 cm gallbladder polyp risks progression of potentially malignant disease 3
• Request multidisciplinary discussion if there are concerns about operative risk, but understand that observation is not a safe option at this size 3
• Do not wait for repeat imaging—the measurement discrepancy is irrelevant when both measurements far exceed the surgical threshold 2, 3

Common Pitfall to Avoid

Do not be falsely reassured by the "smaller" 5 cm measurement. Even if the polyp were actually 5 cm rather than 7 cm, this changes nothing about management—both measurements indicate immediate surgical evaluation 2, 3, 4. The size discrepancy reflects imaging variability, not polyp behavior, and both measurements place you in the highest-risk category requiring intervention 1, 2.