Monitoring of low-risk pancreatic cystic lesions with targeted abdominal ultrasound: diagnostic yield, clinical utility, and acceptance
Article information
Abstract
Purpose
This study aimed to evaluate the utility of targeted abdominal ultrasound (TAUS) for follow-up of low-risk pancreatic cystic lesions (PCLs), assessing diagnostic performance, agreement with advanced imaging, patient acceptance, clinical usefulness, and contribution of structured reporting.
Methods
This prospective study included 120 patients with low-risk PCLs previously characterized by magnetic resonance cholangiopancreatography or endoscopic ultrasound. TAUS was performed using a wideband convex matrix probe (1.8–6.2 MHz) and a structured protocol documenting lesion location, size, morphology (septa, mural nodules), and relation to the main pancreatic duct. Contrast-enhanced ultrasound (CEUS) was used in selected cases. Outcomes included agreement with reference imaging (intraclass correlation coefficient [ICC]), patient preference, and perceived usefulness.
Results
TAUS enabled complete pancreatic visualization in 80.0% of patients and overall detection rate in 88.3%. Detection varied by location (P=0.028), highest in the body (94.5%) and lowest in the tail (68.0%). Agreement for maximal cyst diameter was excellent (ICC, 0.98; 95% confidence interval, 0.971 to 0.986), with 90.8% of measurements within ±20% of the reference modality. When B-mode was suboptimal, CEUS was used in 2.5% of cases and improved delineation of architecture (mural nodules, septations). Limitations included low detection of multifocal disease (11.1%) and restricted assessment of ductal communication (46.6%). TAUS was clinically useful in 78.0% and preferred by patients when characterization was adequate (88.3%).
Conclusion
TAUS is a promising noninvasive imaging tool for monitoring low-risk PCLs in favorable acoustic windows, showing high diagnostic accuracy, excellent agreement with advanced imaging, and strong patient acceptance. Its diagnostic performance is limited in multifocal, complex, or tail-located lesions.
Introduction
Pancreatic cystic lesions (PCLs) are an increasingly common incidental finding, detected in up to 20% of abdominal imaging studies and in more than 75% of individuals over 80 years of age [1–3]. This rising prevalence is associated with population aging and the widespread use of advanced imaging techniques such as computed tomography and magnetic resonance imaging (MRI) [4–7].
Although most PCLs are benign or low-risk, uncertainty about their potential for malignant progression raises clinical concern and justifies prolonged surveillance protocols, typically involving magnetic resonance cholangiopancreatography (MRCP) or endoscopic ultrasound (EUS) [8–10]. However, these techniques have limitations: MRCP entails high costs and limited accessibility, while EUS is invasive, requires sedation, and demands high technical expertise [11–14]. Moreover, their diagnostic accuracy is not absolute; for instance, MRI achieves a sensitivity of 76% and a specificity of 80% in suspicious PCLs, according to a recent meta-analysis [15].
In this context, targeted abdominal ultrasound (TAUS) emerges as a viable, noninvasive, and cost-effective alternative for the structured follow-up of low-risk PCLs. Unlike conventional ultrasound, TAUS is performed systematically and guided by previous imaging, allowing for more accurate assessments and better detection of evolving changes. This study proposes a standardized methodology for TAUS implementation, including image-guided acquisition, uniform evaluation of morphological parameters, and structured reporting, with the goal of improving reproducibility and supporting clinical decision-making.
The aim of this study is to analyze the diagnostic performance, concordance with advanced imaging, and clinical utility of TAUS in the follow-up of low-risk PCLs, as well as to identify its main limitations and areas for improvement.
Materials and Methods
Compliance with Ethical Standards
The study was approved by the Ethics Committee of Hospital Universitario La Paz (approval number: PI-3288), and all participants provided written informed consent after receiving a full explanation of the study, including the potential use of intravenous contrast agents for contrast-enhanced ultrasound (CEUS). The research complied with the principles of the Declaration of Helsinki and current data protection regulations. Confidentiality was ensured through data anonymization and secure information storage systems.
Study Design
This was a prospective, observational study with consecutive inclusion of patients with PCLs under clinical surveillance. All patients underwent TAUS following a structured protocol that assessed lesion anatomical location, maximal diameter, morphology (septa, mural nodules), and relationship to the main pancreatic duct (MPD).
The study analyzed diagnostic performance, agreement with MRCP/EUS, patient acceptance, and physician-perceived clinical usefulness. A predefined interim analysis was planned to assess the stability of key endpoints and determine the final sample size.
Cyst Type Classification
The subtype of each pancreatic cyst was determined based on imaging criteria from MRCP and/or EUS, in accordance with international clinical practice guidelines, including the revised Fukuoka guidelines (2017 [16], updated 2024) [17] and the European evidence-based guidelines (2018) [13]. EUS-guided fine needle aspiration was performed in selected cases, particularly when worrisome features (WF) or high-risk stigmata (HRS) were present, or when imaging findings remained atypical. Cyst fluid was analyzed for glucose, amylase, and carcinoembryonic antigen levels, and mucin viscosity was qualitatively assessed. Cytological evaluation was conducted when sufficient cellular material was obtained. Due to institutional limitations, molecular analysis and other advanced intracystic diagnostic techniques—such as confocal laser endomicroscopy or cystoscopy—were not available. Lesions were classified as indeterminate when the cystic nature could not be confidently established based on imaging, biochemical, and cytological data. Cysts with a microcystic pattern were considered indeterminate only when classic serous cystadenoma features were not met.
Image Review and Risk Adjudication
MRCP and EUS studies were jointly reviewed by an experienced pancreatologist and an abdominal radiologist (each with more than 10 years of experience), who assigned cyst subtype and risk status by consensus according to the aforementioned guidelines. Any disagreements were resolved after joint image review.
Inclusion and Exclusion Criteria
From January 1 to December 31, 2024, we prospectively and consecutively enrolled adults (≥18 years) under surveillance for PCLs at a single tertiary pancreatic clinic (La Paz University Hospital). Eligibility required a reference MRCP or EUS performed within the preceding ≤6 months and adjudication of low-risk status by consensus of an experienced pancreatologist and an abdominal radiologist (each >10 years). Low-risk status was defined—per the revised Fukuoka guidelines (2017; updated 2024) and the 2018 European evidence-based guidelines—by absence of enhancing mural nodules or solid components, MPD <5 mm, cyst size ≤30 mm, and growth <2.5 mm/y. Cases with WF (e.g., MPD 5–9 mm, cyst >30 mm, mural nodules <5 mm, abrupt MPD caliber change with distal atrophy) were eligible only if clinically and radiologically stable for ≥3 years and without any HRS (obstructive jaundice, enhancing solid component or mural nodule ≥5 mm, MPD ≥10 mm, or suspicious/positive cytology). In multifocal disease, at least one lesion ≥5 mm was required to ensure adequate ultrasound visualization; the index (target) cyst—defined as the most representative lesion (largest or with signs of progression)—was selected for analysis. Exclusion criteria were a history of acute or chronic pancreatitis, previous pancreatic surgery, lack of recent reference imaging (MRCP/EUS >6 months), or any HRS at baseline. The selection process is summarized in Fig. 1.
Patient selection flowchart.
Consecutive adults with pancreatic cystic lesions (PCLs) (January–December 2024) were included if magnetic resonance cholangiopancreatography (MRCP)/endoscopic ultrasound (EUS) ≤6 months and consensus low-risk adjudication. Patients with pancreatitis, prior surgery, outdated reference imaging (>6 months), or baseline high-risk stigmata were excluded. Final cohort: 120 (low-risk, n=101; worrisome features [WF], n=19).
Sample Size and Interim Analysis
This was a descriptive study with no predefined hypothesis of superiority and no formal sample size calculation. The final sample size was determined after a predefined interim analysis, which showed stability in key parameters (detection rate, concordance with MRI/EUS, clinical utility, and patient acceptance) from case number 90 onward. Given the low variability observed and the high reproducibility of the results, recruitment was concluded at 120 patients, a number deemed adequate to robustly meet the study objectives.
Ultrasound Examination Protocol
Examinations were performed on an Aplio i800 (Canon Medical Systems, Otawara, Japan) with a broadband matrix probe (1.8–6.2 MHz). Two experienced sonographers (AOM, EMS; >15 years’ experience; ~250 monthly studies each) performed all scans. Patients fasted ≥6 hours. Scans were obtained in supine, left lateral, and right lateral decubitus positions, using deep inspiration with breath-holding, graded compression, postural adjustments, and multiplanar scanning to optimize acoustic windows. Additional maneuvers (e.g., Valsalva, semi-erect positioning) were used selectively; water ingestion was not used.
The mean duration of the pancreatic protocol was ~10 minutes (range, 7 to 15 minutes), depending on window quality and lesion complexity. A structured, segmental approach was used (head, neck, body, tail, and uncinate), guided by reference imaging performed ≤6 months earlier. The objective was to determine whether focused TAUS could detect and characterize the same PCL identified on the reference modality.
A vessel-guided anatomical approach, inspired by Nakao et al. [18], was employed: the splenic vein was the principal landmark for the body/tail, and the portal vein and superior mesenteric artery for the head/uncinate, enabling reproducible insonation of all pancreatic regions.
When B-mode was insufficient to characterize internal features (e.g., suspected mural nodules, complex septations), CEUS was performed in the same session: 2.4 mL sulfur hexafluoride microbubbles (SonoVue, Bracco, Milan, Italy) as an IV bolus, followed by 5 mL saline; low mechanical index (<0.1) with real-time evaluation for ≥90 seconds. Cine-loops were recorded for documentation/offline analysis.
Operational Definitions
Complete pancreatic visualization was defined as the visualization of all pancreatic segments (uncinate, head, neck, body, and tail) within the same session using vascular landmarks; it was considered partial when one or more segments (commonly the tail) could not be adequately assessed despite optimization maneuvers, and non-evaluable when no region could be properly visualized due to a poor acoustic window (e.g., overlying bowel gas, obesity). Detection referred to identification on TAUS of the index (target) cyst previously characterized by MRCP or EUS within the predefined reference interval (≤6 months). Adequate characterization was defined a priori as reporting at least cyst location and maximal diameter on B-mode, with selective CEUS for internal architecture (septa, mural nodules) when B-mode was suboptimal. Unless otherwise specified, percentages for morphology and ductal findings are reported among assessable cases (i.e., those with an adequate acoustic window and clearly visualizable features).
Variables
Ultrasound findings were recorded in a structured report (Table 1), including anatomical location, maximal diameter, number of locules (unilocular; oligolocular <6; multilocular ≥6), wall thickness, septations, mural nodules (and CEUS enhancement), solid components, calcifications, and ductal relationship (clear communication, anatomical contact, or no visible relationship). MPD diameter, pattern of ductal dilatation (segmental/diffuse), strictures, and distal pancreatic atrophy were also documented. This protocol enabled precise morphological characterization and direct comparison with MRCP/EUS, enhancing reproducibility.
Ultrasound parameters collected during TAUS for structured follow-up of PCLs
Satisfaction Survey
Patients indicated their preferred surveillance modality (TAUS, MRCP, or EUS). For those preferring TAUS, reasons (comfort, shorter waits, no radiation, non-invasiveness, availability) were recorded. Responses were summarized as percentages with 95% confidence intervals.
Assessment of Clinical Utility
At the outpatient visit, the referring physician prospectively assessed whether the TAUS report was clinically useful for decision-making. A report was considered “useful” if it enabled establishing, confirming, or adjusting the follow-up plan without immediate advanced imaging. Each examination was classified as “useful” or “not useful."
Statistical Analysis
Continuous variables are summarized as mean±standard deviation or median (interquartile range), and categorical variables as counts and percentages. Agreement for maximal cyst diameter between TAUS and the reference modality (MRCP/EUS) was assessed using a two-way mixed-effects, absolute-agreement, single-measurement intraclass correlation coefficient (ICC) with 95% confidence intervals, and by Bland-Altman (mean difference and limits of agreement). Group comparisons for proportions used the χ2 test (or Fisher’s exact test when appropriate); two-sided P<0.05 was considered statistically significant. Statistical analyses were performed using PSPP, a free open-source software for statistical analysis developed by GNU. Unless otherwise specified, percentages for morphology and ductal findings are reported among assessable cases.
Results
Baseline Characteristics
A total of 120 patients with PCLs evaluated by TAUS were included. All had recent reference imaging studies: MRCP in 75.8% (91/120) and EUS in 24.2% (29/120). The mean age was 66±13 years (range, 20 to 88 years), with a predominance of women (74.2%, 89/120). Baseline characteristics are summarized in Table 2. The most common subtype was branch-duct intraductal papillary mucinous neoplasm (BD-IPMN), identified in 59.2% of cases (71/120), followed by indeterminate cysts (defined as lesions lacking sufficient imaging/biochemical/cytological criteria for definitive classification; a microcystic pattern was counted as indeterminate only if classic serous cystadenoma features were not met) (32.5%, 39/120), including six with a microcystic pattern, and mixed-type IPMN (8.3%, 10/120).
Baseline characteristics of the study population (n=120)
Most patients (77.5%, 93/120) presented with a solitary cyst, while 22.5% (27/120) had multiple lesions, 62% of which measured less than 5 mm. No clinically relevant differences were observed between solitary and multifocal cases.
The mean cyst size was 16.7±12 mm (range, 6 to 65 mm). In patients with multiple cysts, the most representative lesion was analyzed. Size distribution was as follows: <10 mm in 27.2% of cases, 10–19 mm in 47.8%, 20–30 mm in 18.5%, and >30 mm in 6.5%. The most frequent anatomical location was the pancreatic body (45.8%, 55/120), followed by the tail (23.3%, 28/120), dorsal head (14.2%, 17/120), uncinate process (10.0%, 12/120), and neck (6.7%, 8/120).
Regarding cyst morphology, unilocular lesions were the most common (71.3%, 86/120), followed by oligolocular (20.0%, 24/120) and multilocular lesions (8.8%, 10/120).
With respect to WF, 6.5% of patients (8/120) had cysts >3 cm, 8.3% (10/120) presented with MPD dilatation (5–9 mm), and 2.5% (3/120) exhibited mural thickening >3 mm. One patient showed multiple findings, including a 65-mm cyst with a 4-mm mural nodule, MPD dilatation, and distal parenchymal atrophy. In total, 23 WFs were identified across 19 patients (15.8%).
Notably, one lesion initially classified as a branch-duct IPMN in the pancreatic tail (60 mm) was later confirmed by surgical pathology as a mixed-type IPMN with low-grade dysplasia and a gastric foveolar phenotype. Additionally, a 57-mm lesion in the pancreatic tail, initially considered an indeterminate cyst, was surgically resected and definitively diagnosed as a mucinous cystic neoplasm with low-grade dysplasia.
Evaluation by TAUS
The overall detection rate of TAUS was 88.3% (106/120). Complete pancreatic visualization was achieved in 80.0% of patients (96/120), partial visualization in 17.5% (21/120), and the pancreas was not visualized in 2.5% (3/120). The most frequently non-assessable regions were the pancreatic tail in 17.5% (21/120) and the uncinate process in 16.7% (21/120).
The detection rate increased with cyst size, reaching 100% for lesions >30 mm (Fig. 2), and varied significantly by anatomical location (χ2=17.18, P=0.028). The highest detection rates were observed in the pancreatic neck (100%) and body (95%), while the lowest occurred in the tail (68%) (Fig. 3). Clinically, these findings suggest that TAUS is most reliable for cysts located in the neck and body of the pancreas, whereas lesions in the tail or uncinate process are more challenging to visualize due to their posterior location and frequent interposition of bowel gas.
Detection rate of targeted abdominal ultrasound (TAUS) according to pancreatic cyst size.
The detection rate increased progressively with the size of pancreatic cystic lesions, reaching 100% for cysts >30 mm. This pattern supports the effectiveness of TAUS for larger lesions, with lower rates in <10 mm cysts.
Detection rate of targeted abdominal ultrasound (TAUS) according to the anatomical location of pancreatic cystic lesions (PCLs).
The detection of PCLs varies by anatomical region, being highest in the pancreatic neck (100%) and body (95%). The pancreatic tail showed the lowest rate (68%), reflecting technical limitations in areas with suboptimal acoustic access.
While TAUS consistently detected the index cyst in both solitary and multifocal disease, its ability to recognize multifocality (i.e., additional cysts beyond the index lesion) was limited, with additional lesions identified in only 11.1% of patients with multifocal PCLs. This underscores the reduced sensitivity of TAUS for multiple small cysts.
Fig. 4 presents representative examples of imaging correlation between TAUS and MRI across various morphological presentations of PCLs, including unilocular and multilocular forms, located in different anatomical regions, with or without ductal communication or MPD dilatation. These cases demonstrate high concordance between TAUS and MRI in terms of lesion morphology and size, supporting the reliability of TAUS as a complementary modality in selected patients. Fig. 5 shows representative CEUS cases, and Fig. 6 displays the Bland–Altman plot used for agreement analysis with reference imaging techniques.
Correlative imaging between targeted abdominal ultrasound (TAUS) and magnetic resonance imaging (MRI) in various pancreatic cystic lesions.
A. Mixed-type intraductal papillary mucinous neoplasm (IPMN) in the pancreatic tail (60 mm) presents with associated main pancreatic duct (MPD) dilatation. Surgical pathology confirmed low-grade dysplasia with a gastric foveolar phenotype. B. Indeterminate cyst in the pancreatic body (15 mm) shows no visible mural nodules or ductal communication. C. Branch-duct IPMN in the pancreatic body (25 mm) shows stable MPD dilatation and visible ductal communication; maximal MPD diameter 6 mm. D. Indeterminate cyst in the pancreatic tail (57 mm) shows no mural nodules or MPD dilatation. Surgical resection confirmed a mucinous cystic neoplasm with low-grade dysplasia. E. Subcentimetric branch-duct IPMN (8 mm) in the pancreatic body is shown. The lesion is seen on TAUS (epigastric view, left in E); the inset highlights ductal communication (yellow arrow, magnified view); with the corresponding MRI (axial T2 SPACE, right in E). F. Indeterminate cyst in the uncinate process (28 mm) shows no mural nodules or main duct involvement. Cyst sizes (in mm) and the pancreatic duct (pd) are annotated where visible.
Multimodal imaging of two pancreatic cystic lesions assessed by transabdominal ultrasound (TAUS), contrast-enhanced ultrasound (CEUS), and endoscopic ultrasound (EUS).
A–D. An indeterminate microcystic lesion located in the pancreatic body, measuring 15 mm, is shown. A. TAUS in B-mode shows a hypoechoic lesion without clearly defined internal architecture. B. CEUS improves delineation, revealing a microcystic pattern with non-enhancing septa. C, D. EUS B-mode (C) confirms the multilocular architecture, and CE-EUS (D) shows heterogeneous contrast enhancement. No ductal communication was identified. Cytology was inconclusive following EUS-guided aspiration. E–J. A branch-duct intraductal papillary mucinous neoplasm (BD-IPMN) at the body–tail junction, measuring 65 mm, is shown. TAUS B-mode demonstrates internal septations (E), suggests ductal communication (F), and depicts a 4-mm mural nodule (G). CEUS (H) confirms contrast enhancement of the nodule. EUS B-mode confirms lesion size (I) and visualizes the mural nodule (J). CE-EUS also demonstrated enhancement of the mural nodule (images not shown). Cyst sizes (in mm) and the pancreatic duct (pd) are annotated where visible.
Bland-Altman plot comparing cyst diameter measurements by targeted abdominal ultrasound (TAUS) vs. magnetic resonance cholangiopancreatography (MRCP)/endoscopic ultrasound (EUS).
The mean difference was –0.04 mm, with limits of agreement –4.89 to +4.81 mm. Positive values indicate TAUS measured larger diameters than the reference; negative values indicate smaller diameters.
Contrast-Enhanced Ultrasound
CEUS was performed in three patients (2.5% of the cohort). Two cases involved multilocular cysts (20% of all 10 multilocular lesions), in which B-mode TAUS did not allow adequate visualization of internal architecture. The third case corresponded to a unilocular septated cyst with a suspected 4-mm mural nodule.
In all cases, CEUS improved internal characterization: it enhanced septal definition in multilocular lesions and confirmed contrast enhancement of the mural nodule. No adverse events were reported.
Representative CEUS findings are shown in Fig. 5, illustrating its added diagnostic value in complex lesions, with good concordance with EUS in both cases.
Comparison with MRCP/EUS
TAUS demonstrated strong agreement with MRCP/EUS in measuring cyst diameter, with a mean difference of –0.04 mm (ICC, 0.98; 95% confidence interval [CI], 0.971 to 0.986) and Bland-Altman limits of agreement ranging from –4.89 to +4.81 mm (Fig. 6). In 90.8% of cases, TAUS and the reference measurement differed by less than ±20%, confirming a high level of concordance in cyst size estimation.
TAUS also effectively characterized unilocular and oligolocular cysts. In the BD-IPMN subgroup, TAUS provided adequate visualization of the MPD to assess ductal communication in 79 out of 81 cases. Among these, a visible communication between the cyst and the duct was identified in 48.1% (38/79). Detection of ductal communication was higher in mixed-type IPMNs (80.0%, 8/10) than in BD-IPMNs (42.3%, 30/71, based on assessable cases. Notably, TAUS identified 100% of the WF reported in the cohort (n=21), which were present in 19 patients.
Patient Satisfaction
TAUS was the preferred technique among all patients whose cysts could be adequately characterized (88.3%, 106/120; 95% CI, 82.5% to 93.3%). Among them, 95.3% (101/106) cited comfort, lack of radiation exposure, and shorter wait times as the main reasons for their preference. In patients for whom TAUS did not allow adequate characterization (11.7%, 14/120), MRCP was preferred in eight cases (6.7%) and EUS in six cases (5.0%).
Perceived Clinical Utility
The ultrasound report was considered useful for clinical decision-making in 78% of cases (94/120), based on the prospective assessment of the attending physician during follow-up visits. In the remaining 22% of cases, TAUS was not considered clinically useful due to limited acoustic windows or incomplete visualization. However, as TAUS was not intended to replace standard surveillance imaging, these cases continued with follow-up as per clinical guidelines, without modification of the planned management.
A summary of the main study results is presented in Table 3.
Summary of main study results (excluding baseline characteristics)
Discussion
This study assessed the role of TAUS in the follow-up of low-risk PCLs, with a focus on diagnostic performance, agreement with advanced imaging techniques, and clinical applicability.
Detection rates are influenced by multiple factors, notably cyst size, anatomical location, multifocality, patient morphology, and technical parameters. In our study, the overall detection rate was high (88.3%), attributable to the targeted imaging protocol, the use of a broadband convex matrix probe, and prior knowledge of lesion location. This markedly outperforms conventional ultrasound (47.5% detection rate reported by Jeon et al. [19]), highlighting the potential role of optimized TAUS in selected clinical settings.
Cyst size was a key determinant of detection rate: visualization reached 100% for cysts >30 mm, 95% for those measuring 20–30 mm, and 88% in the 10–19 mm group. Even in cysts <10 mm, the detection rate was 80%, exceeding that reported in previous studies such as Sun et al. [20], thereby supporting the efficacy of TAUS for small lesions when performed under optimal conditions.
Anatomical location also influenced detection performance: 100.0% in the neck, 94.5% in the body, 94.1% in the dorsal head, 91.7% in the uncinate process, and 67.9% in the tail. This latter value—substantially higher than the 27% reported by Sun et al. [20] using conventional ultrasound—approaches the performance achieved with the liquid-filled stomach technique [18].
Multifocality was a major limiting factor, with detection rates of 89.1% in solitary cysts compared with 11.1% in multifocal presentations, largely due to the small size of additional lesions (<5 mm in 62.9% of cases). Similar results have been reported in previous studies, confirming that ultrasound is less effective in multifocal settings, particularly in cases of BD-IPMN [21–23]. Therefore, TAUS should not be used as the sole imaging modality in these patients, for whom MRCP or EUS remain more reliable options.
Patient phenotype also influenced examination quality: in 17.5% of cases, pancreatic visualization was incomplete, and in 2.5%, the gland could not be visualized at all. The most challenging regions were the pancreatic tail (17.5%) and uncinate process (16.7%), consistent with previous reports by Sun et al. [20], mainly due to bowel gas interposition or excess adipose tissue. These findings highlight the importance of individualizing the indication for TAUS based on patient morphological characteristics.
While detection is essential, the clinical value of TAUS also lies in its ability to provide sufficient spatial resolution for accurate lesion characterization and monitoring of potential progression. In our series, complete pancreatic visualization was achieved in 80% of cases, and morphological characterization was possible in 88.3%. TAUS showed high concordance with MRCP/EUS in measuring cyst diameter (ICC, 0.98), with a clinically negligible mean underestimation. Similar results were reported by Sun et al. [20] and Li et al. [24].
Morphological characterization was highly accurate in unilocular cysts, with 97% concordance, but performance declined in multilocular or complex lesions, where internal septations and mural nodules were more difficult to assess. In such cases, CEUS provided additional value by improving delineation of the internal architecture, and as described by Li et al. [24], it was required in up to 20% of cases. This added value of CEUS is exemplified in our series, where representative cases (Fig. 5) illustrate improved visualization of internal septations and mural nodules compared with B-mode imaging.
Ductal communication was visualized by ultrasound in 48.1% of evaluable IPMN cases (38/79), with better performance observed in mixed-type IPMN (80%; 8/10) compared to branch-duct forms (42.3%, 30/71), in line with previously published data. Therefore, TAUS is not recommended as a first-line modality for cyst subtype classification, but it may be useful for the follow-up of lesions already characterized by MRCP or EUS.
According to current guidelines, risk stratification in PCLs relies on the presence of WF or HRS [25]. In our cohort, although WFs were infrequent, TAUS successfully detected all documented cases, supporting its value as a structured surveillance tool in carefully selected clinical scenarios.
Beyond its technical performance, TAUS has proven to be effective, accessible, and well accepted by patients, reinforcing its role as a viable follow-up strategy for low-risk PCLs. Its non-invasive nature, absence of radiation or sedation, immediate availability, and low cost contribute to high patient adherence and make it particularly useful in resource-limited settings, where it may reduce costs by up to 68% [26].
In our cohort, TAUS was considered useful for clinical decision-making in 78% of cases, a proportion that closely mirrors the complete pancreatic visualization rate (80%). These findings support its applicability under optimal conditions, including experienced operators, appropriate equipment, and the use of structured reporting.
Regarding study design and population, it is worth noting that the initial target sample size was larger; however, a predefined interim analysis confirmed the stability of key parameters after the 90th case, allowing the study to conclude with 120 patients without compromising its robustness.
Furthermore, the imaging quality achieved with broadband convex matrix probes enabled accurate lesion characterization in most cases. In complex or hard-to-access lesions, complementary techniques—such as CEUS or the liquid-filled stomach method—may further enhance diagnostic performance.
TAUS may be incorporated into hybrid surveillance strategies, alternating with MRI depending on cyst morphology and risk stratification, to optimize resource use while maintaining diagnostic safety.
To fully realize its clinical potential, TAUS must be accompanied by standardized, structured reporting protocols—including lesion location, size, internal morphology, and ductal relationship—are essential.
This was a single-center observational study with a limited sample size, which may restrict the generalizability of the findings—particularly outside specialized centers. The high detection rate may have been influenced by the targeted nature of the examinations, as cyst location was already known in advance, limiting its applicability in screening contexts.
Morphometric data such as body mass index or abdominal fat distribution were not collected, which could have helped assess the impact of body habitus on TAUS performance. Technical limitations were more pronounced in anatomically challenging areas, such as the pancreatic tail and uncinate process, and in the detection of multifocal lesions or subtle morphological findings. Although CEUS was used in selected cases, it did not fully overcome these challenges.
Finally, since this study was not designed to evaluate diagnostic accuracy metrics such as sensitivity or specificity, results should be interpreted as a measure of the practical performance of TAUS in the structured follow-up of previously diagnosed low-risk PCLs.
In this study, the use of TAUS combined with structured reporting demonstrated high detection rates and strong concordance with MRCP/EUS in the evaluation of cyst size and morphology in patients undergoing surveillance for low-risk PCLs. TAUS may serve as a complementary imaging tool in selected patients with favorable anatomy.
Further studies are warranted to define its potential role within broader surveillance strategies for low-risk PCLs.
Notes
Author Contributions
Conceptualization: Marin Serrano E, Saturio Galán N, Gámez-Pozo A, Trilla-Fuertes L, Iturzaeta Sánchez JM, Martin-Arranz MD. Data acquisition: Marin Serrano E, Tello Arnas L, Saturio Galán N, Lalanda-Delgado P, Olveira-Martín A. Data analysis or interpretation: Marin Serrano E. Drafting of the manuscript: Marin Serrano E, Tello Arnas L, Gámez-Pozo A, Olveira-Martín A, Trilla-Fuertes L, Iturzaeta Sánchez JM, Martin-Arranz MD. Critical revision of the manuscript: Marin Serrano E, Saturio Galán N, Lalanda-Delgado P. Approval of the final version of the manuscript: all authors.
Conflict of Interest
No potential conflict of interest relevant to this article was reported.
References
Article information Continued
Notes
Key points
Targeted ultrasound enables effective surveillance of low-risk pancreatic cysts with excellent patient acceptance. This modality demonstrates high diagnostic concordance with magnetic resonance cholangiopancreatography and endoscopic ultrasound for cyst size and morphology in selected patients. Limited performance for multifocal disease and ductal communication restricts universal use; hybrid protocols are advisable.