Keywords gallbladder - polyp - ultrasound - CEUS - neoplasm
Introduction
Gallbladder polyps are projections arising from the gallbladder wall into its lumen.
They are typically discovered incidentally during abdominal ultrasound or post-cholecystectomy,
with an estimated prevalence of up to 9.5% [1 ]. While the majority of these lesions are benign and asymptomatic – such as cholesterol
polyps and inflammatory pseudo-polyps – a small subset may represent true neoplastic
formations with malignant potential [2 ]
[3 ]. Differentiating between benign and malignant polyps remains a critical clinical
challenge, as management strategies range from simple surveillance to surgical intervention
[2 ]
[3 ]
[4 ]
[5 ].
Several risk factors have been associated with their development and potential malignancy
[6 ]. The most consistent and well-established risk factor is polyp size, with lesions
≥10mm carrying a higher risk of neoplastic transformation. Age – particularly over
50 years – and male sex have also been linked to an increased risk [6 ]
[7 ]. Other imaging features such as sessile morphology, rapid growth, and adjacent gallbladder
wall thickening raise suspicion for malignancy [8 ]. Beyond imaging, metabolic factors such as obesity, dyslipidemia, insulin resistance,
and the presence of MASLD may contribute to gallbladder polyp development [8 ]
[9 ]. A recent study observed that metabolic dysfunction-associated steatotic liver disease
(MASLD) itself was not directly associated with polyp development, but a significant
risk emerged in patients with ≥4 MASLD components [10 ]. Men with ≥4 components had a 3.4-fold increased risk of developing polyps ≥6mm,
and women had a 5.3-fold increased risk of developing polyps ≥5mm [10 ]. Additionally, a higher NAFLD fibrosis score was linked to increased polyp risk
in women [10 ]. These findings highlight the need for targeted surveillance of patients with multiple
MASLD components, particularly men with larger polyps and women with advanced liver
fibrosis. Additional factors such as primary sclerosing cholangitis (PSC) and elevated
tumor markers (e.g., CA 19–9) further elevate the suspicion of malignancy [11 ].
Ultrasound is the primary imaging modality for the detection and initial assessment
of gallbladder polyps – due to its widespread availability, non-invasive nature, and
high sensitivity [12 ]
[13 ]
[14 ]. Conventional B-mode imaging enables the characterization of polyp morphology, number,
and size, while Doppler techniques provide insight into vascular patterns that may
indicate malignancy [12 ]
[13 ]
[15 ]. More recently, contrast-enhanced ultrasound (CEUS) and high-resolution techniques
have emerged as valuable tools to further refine diagnosis, allowing for the assessment
of enhancement patterns and wall integrity [4 ]
[16 ]
[17 ]
[18 ].
A recent study evaluated the cost-effectiveness of ultrasound surveillance (USS) for
gallbladder polyps (GBPs) <10mm using a health economic model in a hypothetical UK
cohort of 1000 patients [19 ]. Over a 2-year period, USS incurred substantial additional costs (£213,441–£750,045
for GBPs <6mm and £420,275–£531,297 for GBPs 6–9mm), associated with numerous cholecystectomies
and the prevention of only a small number of gallbladder cancer (GBC) cases (1.3 and
8.7 cases, respectively) [19 ]. The model suggests that the cost of routine USS outweighs potential savings from
avoided GBC treatment and leads to a high rate of potentially unnecessary surgeries
[19 ].
This review aims to provide an updated overview of the current diagnostic and management
strategies for gallbladder polyps based on the latest guidelines and evidence. This
study strives to support clinicians in making informed decisions regarding patient
care, whether through imaging surveillance, additional diagnostic steps such as contrast-enhanced
ultrasound (CEUS), or surgical intervention when warranted.
Key Ultrasound Features
Gallbladder polyps are protrusions of the gallbladder wall extending into the lumen
[1 ]. Polyps do not move into the gallbladder lumen, and they do not cause posterior
acoustic shadowing. They can manifest as either sessile or pedunculated growths. Pseudo-polyps,
which are benign, encompass conditions like cholesterolosis, cholesterinic polyps
and inflammatory polyps ([Fig. 1 ]). True gallbladder polyps may be benign or malignant, with adenomas being the 2nd
most common benign type and adenocarcinomas and metastases representing malignant
forms [20 ] ([Fig. 2 ], [Fig. 3 ]).
Fig. 1 The images show a polyp (white arrow; echogenic structure without shadow) in close
proximity to a gallstone (structure with posterior shadow). The images show the absence
of color Doppler signals within the polyp as in a pseudo-polyp (cholesterol polyp).
Fig. 2 The images show a polyp of the fundus of the gallbladder. In detail, the color study
highlights a vascular peduncle (white arrow), which suggests the diagnosis of “true
polyp”.
Fig. 3 Polypoid “cluster” structure (details with linear high frequency probe) protruding
into the lumen of the gallbladder. Irregular margins, growth into the lumen of the
gallbladder, alteration of the wall profile, and size > 15mm suggest a diagnosis of
malignancy.
Pseudo-polyps (e.g., cholesterol or inflammatory) are typically small, often under
5mm, tend to be multiple with a smooth outline, and typically lack internal vascular
flow on Doppler examination [21 ]; they usually present as highly echogenic on ultrasound and may show a characteristic
“comet tail” or ring-down artifact [1 ]. Benign polyps (e.g., adenomas) are often solitary and can be slightly larger than
pseudo-polyps; they generally have a smoother, more uniform contour and may exhibit
minimal or no detectable flow with Doppler. Moreover, they usually have a stable size
and appearance on serial imaging [1 ]. Malignant polyps are often larger than 10mm and may have an irregular or lobulated
contour and heterogeneous internal echoes or mixed echogenicity ([Fig. 3 ]) [21 ]; they frequently demonstrate internal vascular flow on Doppler, and they are often
associated with focal or diffuse gallbladder wall thickening and signs of local invasion
([Fig. 4 ]) [1 ].
Fig. 4 Polypoid wall structure at the fundus level with sessile growth and alteration of
the wall profile. A “disorganized” polyp vascularization is evident without a clear
and single vascular pedicle.
Pseudo-polyps typically do not enhance on CEUS [22 ]. On CEUS, benign true polyps (adenomas) are often characterized by homogeneous enhancement
without rapid washout [22 ]. Otherwise, malignant polyps display rapid washout on CEUS ([Table 1 ]) [22 ].
Table 1 Comparative table summarizing the typical B-mode ultrasound (US), Doppler, and contrast-enhanced
ultrasound (CEUS) findings for pseudo-polyps versus true gallbladder polyps (benign
and malignant).
Type of Polyp
B-Mode Ultrasound features
Doppler features
CEUS features
Pseudopolyps (e.g., cholesterol, inflammatory)
No internal vascular flow on color Doppler
Inflammatory polyps can show minimal flow if inflamed, but usually negligible
Benign True Polyps (e.g., adenomas)
Often solitary
May be slightly larger than pseudo-polyps (5–10mm)
Smooth or slightly lobulated contour
Uniform internal echogenicity
May remain stable on follow-up
Malignant Polyps (e.g., adenocarcinoma, metastasis)
Usually > 10mm
Irregular or lobulated contour
Heterogeneous echogenicity
Possible adjacent gallbladder wall thickening (focal or diffuse)
Features suggestive of local invasion or infiltration (e.g., liver)
Heterogeneous hyper-enhancement in arterial phase
Rapid washout in venous phase
Possible early involvement of gallbladder wall
May show infiltration into surrounding tissues
Additionally, other rare benign and malignant true gallbladder polyps exist, such
as mesenchymal tumors and lymphoma metastasis. Ultrasound has a sensitivity and specificity
of 83.1% and 96.3%, respectively, with a positive predictive value of 14.9% (7.0%
for malignant polyps) and a negative predictive value of 99.7% for the diagnosis of
true polyps of the gallbladder [23 ].
Update on Gallbladder Polyps
Update on Gallbladder Polyps
Recent guidelines on gallbladder polyps have been published by the Society of Radiologists
in Ultrasound (SRU) in 2022 [24 ]. Those guidelines divide polyps into intermediate, low, or extremely low risk of
malignancy depending on their morphology, wall thickening, and size [24 ]. The authors suggested that when an ultrasound examination is inconclusive for polyps,
a short-term follow-up (1–2 months) is recommended. Moreover, CEUS/magnetic resonance
imaging (MRI) or short-term follow-up are recommended when it is not possible to differentiate
between wall polyp or sludge or adenomyomatosis [24 ]. A specialist consultation should be requested when there is a high suspicion of
cancer or a positive history of primary sclerosing cholangitis (PSC), in particular,
aspects suggestive of the invasion of the wall, presence of concomitant neoplastic
liver lesions, biliary obstruction, presence of pathological lymph nodes [24 ]. There are different dimensional cut-offs for the surgical indication. Furthermore,
if ultrasound follow-up shows an increase in polyp size > 4mm in less than 1 year
or the polyp reaches the threshold size, surgical consultation is indicated [24 ]. On the contrary, if there is a decrease in the size of the polyp > 4mm, interruption
of follow-up is indicated [24 ].
Based on those recommendations, recent studies showed a substantial agreement for
polyp risk categorizations and surgical consultations based on the SRU 2022 guidelines
among abdominal radiologists [25 ]
[26 ]
[27 ]. Jeans et al. analyzed 251 patients with 407 gallbladder polyps, most of which were
small (<10mm) and classified as either extremely low risk (51.6%) or low risk (48.2%),
with only one intermediate-risk case, according to the SRU classification [28 ]. Follow-up was deemed unnecessary for 88.4% of polyps, and among those monitored,
nearly 90% remained stable, decreased, or resolved [28 ]. Of 28 patients who had surgery, only 2 had neoplastic polyps, including one invasive
carcinoma [28 ].
In 2022, further multi-society guidelines were published, which more clearly divides
true polyps according to whether they are larger or smaller than 1cm; pseudo-polyps
are immediately excluded from the diagnostic process [29 ]. Cholecystectomy is suggested in the absence of contraindications in the case of
true polyps > 1cm in size [29 ]. If the polyp is less than 1cm, the symptoms and a series of risk factors such as
advanced age (> 60 years), primary sclerosing cholangitis, Asian ethnicity, and morphology
of the polyp are considered [29 ]. If the polypoid lesion grows and exceeds 10mm during follow-up, cholecystectomy
becomes recommended [29 ]. If the polypoid lesion grows 2mm or more within a 2-year follow-up period, the
current size of the polypoid lesion should be considered along with the patient's
risk factors [29 ]. Multidisciplinary discussion can be used to decide whether to continue monitoring
or whether cholecystectomy is indicated [29 ].
There is a further World Federation of Ultrasound in Medicine and Biology (WFUMB)
position paper, also published in 2022, that recommends cholecystectomy when the polyp
size exceeds 1cm. High-resolution endoscopic ultrasound (EUS) and CEUS may be performed
before cholecystectomy to evaluate malignancy risk and potential infiltration [30 ].
In the case of polyps measuring 7–9mm, in patients without individual risk factors
for malignancy or suspicious B-mode US features apart from size, follow-up after 6,
12, and 24 months is recommended [30 ]. Evaluation using high-resolution and/or CEUS or EUS may be performed in patients
with individual risk factors (Indian ethnicity, history of primary sclerosing cholangitis
[PSC], age >50 years] or B-mode US features associated with increased/high risk of
malignancy or growth ≥ 2mm [30 ]. Otherwise, surgical treatment should be offered to patients with Indian ethnicity,
PSC, and/or ultrasound features (B-mode ultrasound, high-resolution EUS, CEUS) associated
with a high risk of malignancy [30 ].
In the case of a polyp < 7mm, in patients without individual risk factors or suspicious
B-mode ultrasound features, no evaluation, no follow-up, and no treatment are recommended
[30 ]. Follow-up after 6, 12, and 24 months should be considered in patients with Indian
ethnicity or a history of PSC and/or patients with B-mode ultrasound features associated
with increased/high risk of malignancy [30 ]. Follow-up can be stopped when gallbladder polyps disappear, there is no growth
(≥2mm to ≥10mm), no ultrasound high-risk features are observed within 24 months, and
no individual risk factors are present [30 ].
Moreover, the authors suggested technical details such as measurement in the long
axis of the gallbladder polyp, which can be supplemented by measurement perpendicular
to the long axis (short axis) to give the height/width ratio as a parameter to describe
polyp shape [30 ]. In the case of multiple polyps, their number should be indicated (at least up to
5 or 10); indeed, the measurement of the largest gallbladder polyp is sufficient [30 ].
The Italian Society of Ultrasound in Medicine and Biology (SIUMB) guidelines argued
in 2023 that criteria used in the therapeutic clinical management of polypoid lesions
of the gallbladder should take into account the size of the polyp and the presence
of some risk factors of malignancy (age > 50 years; presence of PSC; Indian ethnicity,
sessile polyp with thickening of the gallbladder wall > 4mm) [31 ]. Polyps ≥ 10mm in size have an increased risk of malignancy and specialist evaluation
should be recommended [31 ]. However, if the patient has no risk factors, annual ultrasound follow-up is suggested
when the polyp is < 6mm or every 6 months when the polyp is between 6 and 9mm [31 ].
The 2025 guidelines from the Korean Society of Abdominal Radiology (KSAR) provide
comprehensive recommendations for the interpretation, reporting, and management of
incidentally detected GBPs and gallbladder wall thickening, emphasizing the role of
ultrasound as the primary diagnostic tool [32 ]. For size measurement, the guidelines recommend using the longest diameter from
outer margin to outer margin, including the stalk in pedunculated polyps but excluding
any associated wall thickening [32 ]. Risk stratification plays a key role in guiding follow-up and treatment. GBPs less
than 6mm in size without concerning imaging features – defined as adjacent wall thickening,
a sessile morphology, or significant growth – are considered likely benign and typically
do not require follow-up [32 ]. For polyps measuring between 6 and 9mm, management decisions should be based on
the patient’s age and the presence of these suspicious features [32 ]. If warranted, surveillance includes biannual ultrasound during the first year,
followed by annual scans for up to 4 additional years [32 ]. Polyps 10mm or larger raise suspicion for neoplastic transformation, particularly
when suspicious features are present [32 ]. Routine use of CT or MRI is not recommended for incidentally detected GBPs. However,
these modalities may be considered when ultrasound is inconclusive, when malignancy
is suspected, or during preoperative planning for cholecystectomy [32 ]. CEUS is also not recommended routinely but may be useful in evaluating GBPs ≥10mm
if surgery is deferred, or when CT and MRI are contraindicated [32 ]. Doppler ultrasound, while limited with respect to differentiating between benign
and malignant lesions, can still be used to assess vascularity, especially when interpreted
alongside B-mode imaging [32 ]. Surgical management by means of cholecystectomy is advised for patients who are
candidates for surgery and have GBPs measuring ≥15mm, or those with GBPs between 10
and 14mm if suspicious imaging features are present [32 ]. Cholecystectomy may also be considered in patients aged 50 or older with polyps
measuring 6–9mm that show suspicious features [32 ]. Conversely, GBPs between 10 and 14mm without such features may be managed conservatively
with regular follow-up [32 ]. Demographic risk factors such as older age, Asian ethnicity, and PSC are recognized
as relevant, but the guidelines advise against incorporating these non-imaging factors
into radiology reports, except in the presence of elevated tumor markers like CA 19–9
[32 ]. Additionally, the presence of gallstones alone should not be viewed as indicative
of malignancy. Instead, a thorough ultrasound evaluation should be performed to ensure
an accurate risk assessment [32 ].
A summary of findings about ultrasound features of polyps and recommendations of different
societies are listed in [Table 2 ], [Table 3 ], [Table 4 ].
Table 2 Main features on B-mode ultrasound about gallbladder polyps and corresponding risk
of malignancy. Gallbladder: GB; gallbladder polyps: GBP. Adapted from Jenssen C et al. Ultrasound Med Biol. 2022.
US feature of GBP
Predictive of
Risk of malignancy
Solitary
Neoplastic polyps and focal adenomyomatosis
Increased
Multiple
Cholesterol polyps
Low
Sessile with disruption and/or focal thickening of GB wall ≥4mm
Neoplastic polyp
High
Sessile, without wall disruption and without thickening of GB wall ≥4mm
Benign polyps and focal adenomyomatosis
Increased
Pedunculated
Cholesterol polyps and other benign GBPs
Low
Surface irregular/lobulated
Neoplastic and benign fibro-myoglandular polyps
Increased
Surface smooth
Cholesterol polyps
Low
Small cysts
Focal adenomyomatosis
Low
Reverberation artifacts
Focal adenomyomatosis, cholesterol polyps
Low
Hyperechoic foci
Cholesterol polyps, focal adenomyomatosis
Low
Focal GB wall disruption
Malignant GBP, focal adenomyomatosis
Increased
Table 3 Comparison of management recommendations for gallbladder polyps based on their size
and follow-up between different guidelines. Society of Radiologists in Ultrasound:
SRU; European Society of Gastrointestinal and Abdominal Radiology: ESGAR; European
Association for Endoscopic Surgery and other Interventional Techniques: EAES; International
Society of Digestive Surgery-European Federation: EFISDS; European Society of Gastrointestinal
Endoscopy: ESGE; World Federation of Ultrasound in Medicine and Biology: WFUMB; Italian
Society of Ultrasound in Medicine and Biology: SIUMB; Korean Society of Abdominal
Radiology: KSAR; gallbladder: GB; GB polyp: GBP; GB wall thickening: GBWT; ultrasound:
US; primary sclerosing cholangitis: PSC. *GB-related symptoms: pain in the upper right
abdomen, nausea, or vomiting.
SRU guidelines
ESGAR, EAES, EFISDS, ESGE guidelines
WFUMB position paper
SIUMB guidelines
KSAR guidelines
< 6.0 mm
Extremely low risk: no follow-up
Low risk: no follow-up
Indeterminate risk: US follow-up at 6, 12, 24, 36 months vs. surgical consult
In the case of GB-related symptoms*: surgical consult;
If there are no GB-related symptoms, no risk factors for malignancy: follow-up not
required;
If there are no GB-related symptoms, with risk factors for malignancy: US follow-up
at 6 months, 1 year, and 2 years
In the case of patients without risk factors or suspicious B-mode US features: no
evaluation, no follow-up and no treatment are recommended.
In the case of patients with Indian ethnicity or history of PSC and/or suspicious
US features: US follow-up at 6, 12, 24 months
Annual US follow-up
No follow-up for GBPs without suspicious features
Follow-up in the case of adjacent GBWT, sessile morphology
6.1–9.0mm
Extremely low risk: no follow-up
Low risk: US follow-up at 12 months
Indeterminate risk: surgical consult
In the case of GB-related symptoms: surgical consult;
If there are no GB-related symptoms, no risk factors for malignancy: US follow-up
at 6 months, 1 year, and 2 years
If there are no GB-related symptoms, with risk factors for malignancy: surgical consult
In the case of patients without risk factors for malignancy or suspicious B-mode US
features: follow-up after 6, 12, and 24 months.
In the case of patients with Indian ethnicity, PSC and/or US features associated with
high risk of malignancy: surgical consult
US follow-up every 6 months
US follow-up based on age and suspicious features. If needed: US every 6 months in
first year, then annually for 4 years
Optional surgery if suspicious features present and patient age ≥50
9.1–15.0mm
Extremely low risk: US follow-up at 6, 12, 24 months
Low risk: US follow-up at 6, 12, 24, 36 months vs. surgical consult
Indeterminate risk: surgical consult
Surgical consult
Surgical consult
Surgical consult
>15.0mm
Extremely low risk: surgical consult
Low risk: surgical consult
Indeterminate risk: surgical consult
Surgical consult
Surgical consult
Surgical consult
Surgery recommended in suitable patients
Table 4 Comparison of follow-up strategies for gallbladder polyps based on their size and
follow-up between different guidelines. Society of Radiologists in Ultrasound: SRU;
European Society of Gastrointestinal and Abdominal Radiology: ESGAR; European Association
for Endoscopic Surgery and other Interventional Techniques: EAES; International Society
of Digestive Surgery-European Federation: EFISDS; European Society of Gastrointestinal
Endoscopy: ESGE; World Federation of Ultrasound in Medicine and Biology: WFUMB; Italian
Society of Ultrasound in Medicine and Biology: SIUMB; Korean Society of Abdominal
Radiology: KSAR; gallbladder: GB; ultrasound: US; primary sclerosing cholangitis.
SRU guidelines
ESGAR, EAES, EFISDS, ESGE guidelines
WFUMB position paper
SIUMB guidelines
KSAR 2025 guidelines
Follow-up
If GB polyp increases > 4mm in less than 1 year or reaches threshold size: surgical
consult;
If GB polyp decreases > 4mm: stop follow-up
US follow-up should be discontinued after 2 years in the absence of growth
Follow-up can be stopped when GB polyps disappear, there is no growth (≥2mm to ≥10mm),
no US high-risk features are observed within 24 months and no individual risk factors
are present
Not specified
Biannual US in year 1, then annually for 4 years.
Consider significant growth to be a change in size that results in a polyp moving
from one size category to another.
Discontinue after 5 years if stable.
No follow-up needed for resolved polyps.
Critical Revision of Guidelines and Recent Evidence
Critical Revision of Guidelines and Recent Evidence
From the comparison of those recent guidelines, strong points of agreement emerge,
together with unclear aspects among the different recommendations.
The first point is that pseudo-polyps, when diagnosed using the color Doppler ultrasound
method and with the possible aid of CEUS, are not included in the follow-up criteria
or possible surgical procedures, as they are considered certainly benign lesions.
Secondly, the finding of a true polyp in a patient with symptoms attributable to biliary
and gallbladder problems is preferentially a candidate for surgery, in the absence
of contraindications [29 ]
[33 ]. Third, when it comes to dimensional assessment, there is unanimous agreement that
a polyp > 15mm in size should be treated surgically. Even concerning polyps between
10 and 14.9mm, there would be general agreement regarding the recommendation for surgery,
apart from the SRU guidelines, which introduces a qualitative and morphological evaluation
of the polyp and the underlying gallbladder wall [24 ]. If the polyp is placed in the extremely low-risk category, ultrasound follow-up
is indicated. However, uncertainty remains between the 2 strategies when the polyp
is considered low-risk [24 ].
The category of polyps measuring between 7 and 9mm is characterized by greater heterogeneity
in recommendations: while the SIUMB guidelines recommend an ultrasound follow-up every
6 months [31 ], the other 3 guidelines attempt to categorize these polyps into different risk classes
based on ultrasound/morphological factors, symptoms, age, ethnicity, and any associated
biliary tract pathology (PSC) [24 ]
[29 ]
[30 ]. Therefore, they range from truly low-risk polyps in SRU, in which follow-up is
not even indicated, to recommendations for surgery when symptoms or risk factors are
present.
The recommendations regarding the category of polyps with dimensions < 6mm are also
quite heterogeneous. The SIUMB guidelines offer a clear recommendation, proposing
annual ultrasound follow-up [31 ]. Other guidelines recommend not performing an ultrasound follow-up in the absence
of risk factors and/or ultrasound features suspicious for malignancy. Otherwise, an
ultrasound check is recommended every 6 months [24 ]
[29 ]
[30 ].
Even with respect to the decision-making criteria for follow-up, there is clear heterogeneity
regarding both timing and size criteria. Two of the guidelines also provide a time
criterion (2 years) for suspending follow-up [29 ]
[30 ].
Therefore, a simplified step-by-step diagnostic-clinical approach could be extrapolated
as follows ([Fig. 5 ]):
Fig. 5 Flowchart showing the step-by-step diagnostic-clinical approach to a gallbladder polypoid
lesion.
Establish a differential diagnosis between a true polyp vs. a pseudo-polyp (to continue
when true polyps are found or in the case of uncertainty)
Evaluation of symptoms reported by the patient (related to gallbladder and biliary
tract diseases) if present, surgical indication
Dimensional evaluation: if polyp > 15mm surgical indication
If the polyp is between 10–14mm surgical indication, unless the polyp is classified
as extremely low risk or low risk based on morphological criteria. In this instance,
ultrasound follow-up is indicated.
If a polyp is between 7–9mm evaluate ultrasound morphology and clinical risk factors
surgical indication if present, follow-up if absent.
If a polyp < 6mm evaluate ultrasound and clinical risk factors ultrasound follow-up
if present.
Recent evidence has pointed out the relevant role of gallbladder wall thickening (GWT),
often related to polyps. The Gallbladder Reporting and Data System (GB-RADS) is a
recently developed system aimed at assessing and determining risk levels in non-acute
scenarios [34 ]. The diagnosis of benign GWT (GB-RADS 2) relies on identifying a layered appearance
or detecting intramural cysts and echogenic foci [34 ] ([Table 5 ]). The layered appearance, which involves seeing both the inner and outer layers
of the gallbladder, is most commonly associated with diffuse GWT. However, in cases
of malignant GWT, this characteristic layered structure is lost, due to the disruption
of the mucosa and the infiltration of tumor cells into the deeper layers of the GB
wall [35 ]. Intramural findings, including intramural cyst and echogenic foci, suggest benign
GWT and may present in either a focal or diffuse pattern [34 ]. Intramural cysts, seen as anechoic areas within the thickened gallbladder wall,
correspond to enlarged Rokitansky-Aschoff sinuses (RAS) and are considered characteristic
of adenomyomatosis (ADM). Conversely, intramural hyperechoic foci are caused by the
accumulation of cholesterol crystals within the RAS [36 ]. An indistinct gallbladder-liver interface may suggest infiltration by gallbladder
cancer, with this feature showing high specificity and a positive predictive value
for diagnosing malignant GWT, corresponding to GB-RADS 4. A clear diagnosis of extramural
extension is made when the gallbladder lesion affects surrounding bile ducts or blood
vessels, or when an extramural mass is observed infiltrating the liver. These ultrasound
findings make the likelihood of GBC very high, classifying the case as GB-RADS 5 [34 ]. A recent study indicates that while there is generally good inter-reader agreement
regarding GB-RADS categories, agreement on individual findings within the system is
less reliable [37 ]. The study also highlighted that the GB-RADS 2 category carries a very low risk
of malignancy, whereas the GB-RADS 5 category presents the greatest malignancy risk
[37 ] ([Fig. 6 ], [Fig. 7 ], [Fig. 8 ]).
Table 5 The Gallbladder Reporting and Data System (GB-RADS). Adapted from Gupta P. et al.
Gallbladder reporting and data system (GB-RADS) for risk stratification of gallbladder
wall thickening on ultrasonography: an international expert consensus. Abdom Radiol
(NY). 2022. CT: computed tomography, MRI: magnetic resonance imaging, US: ultrasonography.
GB-RADS score
Risk category
Findings
Management
0
Inadequate evaluation due to technical or patient factors or gallbladder-related factors
Morbid obesity
Repeat ultrasound in selected cases
Consider multiphasic contrast-enhanced CT/MRI after multidisciplinary discussion
Wall-echo-shadow complex
Porcelain gallbladder
Gas in the gallbladder lumen
1
Normal
Adequate gallbladder distension
No additional imaging or follow-up is needed
Wall thickness ≤ 3mm
2
Benign (risk of malignancy <2%)
Symmetric circumferential thickening with or without intramural changes or focal thickening
with intramural changes
No additional imaging or follow-up needed
Layered appearance
Preserved interface with liver
3
Equivocal (risk of malignancy 2–50%)
Circumferential thickening without layered appearance
Consider multiphasic contrast-enhanced CT/MRI after multidisciplinary discussion
Focal thickening without intramural features (cysts or echogenic foci) or layered
appearance
Distinct interface with liver
4
Malignancy is likely (risk of malignancy 50–90%)
Circumferential or focal thickening without layered appearance and with loss of interface
with liver
Multiphasic contrast-enhanced CT/MRI
5
Malignancy is highly likely (risk of malignancy > 90%)
Same as GB-RADS 4 with definite extramural invasion as suggested by one of the following:
Multiphasic contrast-enhanced CT/MRI
Biliary or vascular involvement by direct extension of mural thickening
Liver mass in contiguity with the mural thickening
Fig. 6 Large eccentric hypoechoic thickening of the gallbladder wall with infiltrative aspects
on the liver parenchyma (GB-RADS 5).
Fig. 7 CEUS (0:40 minutes) at the gallbladder wall thickening typified as GB-RADS 5: the
lesion presents hyper-enhancement in the arterial phase, with subsequent washout in
the portal and late phases. CEUS allows better delineation of the infiltrative portion
of the mass towards the liver parenchyma.
Fig. 8 CEUS (4:00 minutes) at the gallbladder wall thickening typified as GB-RADS 5: the
lesion presents hyper-enhancement in the arterial phase, with subsequent washout in
the portal and late phases. CEUS allows better delineation of the infiltrative portion
of the mass towards the liver parenchyma.
In a recent study by Wang and colleagues, the incidence of malignant tumors increased
markedly across higher GB-RADS categories, ranging from 9% in GB-RADS 2 up to 100%
in GB-RADS 5 [38 ]. GB-RADS achieved an AUC of 0.855, with solid but not optimal sensitivity, specificity,
and accuracy values [38 ]. Notably, the addition of color Doppler flow imaging (CDFI) to GB-RADS considerably
boosted these diagnostic metrics. The combined approach yielded an AUC of 0.965, reflecting
a high level of reliability in differentiating malignant from benign lesions [38 ]. Finally, the high Kappa value (0.870) indicated excellent inter-observer agreement,
suggesting that both experienced radiologists and less-seasoned practitioners could
consistently apply the combined method [38 ].
New Insights on the Role of CEUS
New Insights on the Role of CEUS
Notably, in the main diagnostic algorithms proposed, there is no reference to a specific
role of CEUS. According to the 2018 EFSUMB guidelines, adenomas are characterized
by a wide vascular stalk that is best seen on CEUS [22 ]. Moreover, polyps > 10mm which show an iso- and inhomogeneous enhancement pattern
may be a criterion to differentiate adenomas from cholesterol polyps [22 ]. A study by Zheng et al. showed sensitivity, specificity, and accuracy rates of
94.1%, 95.5%, and 95.2%, respectively, for CEUS with regard to distinguishing between
benign and malignant gallbladder lesions [39 ]. Sludge masses remained unenhanced, while polyps and adenomas predominantly exhibited
homogeneous hyper-enhancement in the arterial phase and iso-enhancement in the venous
phase [39 ]. Conversely, tumors typically appeared heterogeneously hyper-enhanced in the arterial
phase and exhibited rapid washout in the venous phase [40 ]. Notably, CEUS was particularly beneficial with regard to improving diagnostic accuracy
for polyps larger than 10mm in size [39 ].
According to the SIUMB 2023 guidelines, adenomatous polyp vascularization is characterized
by regular vessels with a tree-like distribution [31 ]. CEUS appearance is generally characterized by hyper-enhancement in the arterial
phase, followed by iso-enhancement in the venous phase or, more rarely, by hypo-enhancement
[31 ]. The gallbladder wall appears intact, and the surrounding tissue appears normal,
without any signs of invasion [41 ]. Moreover, washout of the lesion ≤ 28s is more frequent in malignant lesions [31 ]. Gallbladder metastases exhibit moderate to intense contrast enhancement in the
arterial phase, followed by a more or less fast washout in the venous phase [42 ]. Furthermore, CEUS can better highlight any wall thickening associated with polyps,
a finding indicative of an increased risk of malignancy [40 ] ([Table 6 ]). It is specified that the studies refer to the contrast medium sulfur hexafluoride.
Table 6 Main features of gallbladder polyps (GBP) on contrast-enhanced ultrasound (CEUS) and
relative risk of malignancy. Adapted from Jenssen C et al. Ultrasound Med Biol. 2022.
CEUS feature of GBP
Risk of malignancy
Arterial hyper-enhancement
Increased
Heterogeneous enhancement
High
Irregular vessel pattern
High
Late-phase hypo-enhancement
High
Homogeneous enhancement
Low
Continuous mucosal layer enhancement
Low
Washout < 28s
High
Conclusion
Ultrasound is a fundamental tool in the diagnosis and characterization of gallbladder
polyps. B-mode imaging allows for the identification of echogenic formations attached
to the gallbladder wall, while advanced techniques such as color Doppler, power Doppler,
and micro-flow enable a thorough assessment of polyp vascularization, distinguishing
between benign pseudo-polyps, such as cholesterol polyps, and potentially neoplastic
formations. The integration of CEUS further improves diagnostic accuracy, confirming
the integrity of the wall and the absence of pathological washout, which is characteristic
of malignant lesions. Overall, ultrasound and its advanced modalities provide a non-invasive,
effective, and accurate approach for the differential diagnosis of gallbladder polyps,
aiding clinicians in the management and follow-up of patients.
