SRU Gallbladder Polyp Calculator (2022 Guidelines)

The 2022 Society of Radiologists in Ultrasound (SRU) consensus recommendations provide a risk-stratified approach to incidentally detected gallbladder polyps on ultrasound. Most sonographically detected gallbladder polyps smaller than 10 mm are nonneoplastic, commonly cholesterol or inflammatory polyps. The SRU framework was developed to reduce unnecessary surveillance and surgery while identifying lesions that warrant follow-up or surgical consultation on the basis of morphology, size, and interval change.^[1]

The 2026 Canadian Association of Radiologists update reviewed the SRU recommendations and the more conservative European guidelines and supported the SRU morphology-based, risk-stratified approach.^[3]

When the SRU Algorithm Applies

The SRU pathway is intended for incidentally detected gallbladder polyps evaluated with ultrasound. It should not be applied to patients with primary sclerosing cholangitis (PSC). In patients with PSC, the SRU consensus recommends referral to applicable gastroenterology or other specialty guidance because the malignancy risk and management considerations differ.^[1][2]

A lesion with imaging features suspicious for an invasive or malignant gallbladder tumor should not be managed through routine SRU polyp surveillance. Such findings warrant specialist evaluation rather than application of the routine polyp algorithm.^[1]

If the ultrasound examination is technically inadequate, the suspected polyp is poorly seen, or the gallbladder is not adequately distended, the SRU consensus supports repeat ultrasound within 1-2 months using optimized grayscale and color or power Doppler technique and appropriate patient preparation.^[1]

For a gallbladder lesion larger than 10 mm that cannot be confidently distinguished from tumefactive sludge or adenomyomatosis, the SRU consensus supports short-interval repeat ultrasound within 1-2 months using optimized technique and patient preparation. Contrast-enhanced ultrasound may be used for additional characterization, and MRI may be considered when contrast-enhanced ultrasound is unavailable.^[1]

SRU Gallbladder Polyp Risk Categories

The SRU system uses three morphology-based categories.^[1]

Extremely Low Risk

• Pedunculated with a ball-on-the-wall appearance.
• Pedunculated with a thin stalk.

Low Risk

• Pedunculated with a thick or wide stalk.
• Sessile.

If morphology is uncertain between the Extremely Low Risk and Low Risk categories, the SRU consensus supports using the Low Risk category.^[1]

Indeterminate Risk

Indeterminate Risk applies when there is focal gallbladder wall thickening of 4 mm or greater adjacent to the polyp that cannot be attributed to wall edema, a mucosal fold, adenomyomatosis, or gallbladder underdistention.^[1]

For an otherwise Extremely Low Risk polyp, the SRU recommendations allow optional management as Low Risk when relevant geographic or genetic risk is known, including populations with higher gallbladder cancer incidence.^[1][2][3]

Age, coexisting gallstones, polyp vascularity, polyp echogenicity, and the number of polyps are not incorporated into SRU risk stratification.^[1][2]

Management by Risk Category and Size

Polyp size should be rounded to the nearest millimeter before applying the SRU thresholds.^[1][3]

These thresholds are specific to the SRU pathway. Other international gallbladder polyp guidelines use different risk factors and management thresholds.^[1][3]

Interval Change During Surveillance

The SRU recommendations recognize that small changes in polyp size can occur as part of the natural history of nonmalignant polyps. Growth of 4 mm or more within 12 months is considered rapid growth.^[1]

• An increase of 4 mm or more within 12 months warrants surgical consultation.
• Reaching the surgical-consultation size threshold for the applicable SRU category warrants surgical consultation.
• A decrease of 4 mm or more supports stopping follow-up.

The 2024 SRU clinical-scenarios review further clarifies application of the decrease criterion to shrinking polyps under surveillance.^[2][3]

The published SRU follow-up pathway specifies interval-change and surgical-threshold triggers. It does not provide a separate instruction to restart the original baseline surveillance schedule solely because the current follow-up size has entered another surveillance size band. Accordingly, this calculator preserves an already established SRU surveillance plan when none of the defined follow-up triggers is met.^[1][2]

Imaging and Reporting Considerations

Morphology should be assessed carefully because it determines the initial SRU category. A thin stalk may be difficult to visualize directly on grayscale ultrasound and may sometimes be inferred from lesion motion or a small vascular stalk. Sessile lesions have a broad-based attachment without a stalk.^[1]

Focal wall thickening adjacent to a polyp deserves particular attention. Thickening of 4 mm or greater is considered an Indeterminate Risk feature only after alternative explanations such as edema, mucosal folds, adenomyomatosis, and underdistention have been excluded.^[1]

Detectable vascularity alone does not move a polyp into a higher SRU category. Likewise, echogenicity and multiplicity are not used to alter SRU risk stratification.^[1][2]

Surgical consultation is not equivalent to an automatic recommendation for cholecystectomy. Surgical decision-making is multifactorial and should account for patient health, operative risk, imaging findings, and shared decision-making.^[1]

Important Limitations

The SRU recommendations combine published evidence with expert consensus. The evidence base for gallbladder polyp malignancy risk is limited by selection bias in surgical series, relatively low event rates, and incomplete knowledge of the natural history of small and intermediate-sized polyps.^[1][3]

This calculator implements the SRU pathway. It should not be interpreted as a universal gallbladder polyp guideline or as a replacement for radiologist judgment, clinical context, specialist consultation, or local practice standards.

Frequently Asked Questions (FAQs)