The Triage Role of Transabdominal Ultrasonography (TAUS) in the Diagnostic Management of Pancreatic and Distal Biliary Pathologies: A Comparative Efficacy Analysis with Endoscopic Ultrasonography (EUS)

Background/Objectives: The diagnostic management of obstructive pancreatobiliary pathologies often leads to unnecessary invasive procedures and the overuse of costly imaging due to inherent diagnostic uncertainties. This dilemma highlights the need for a refined triaging strategy. This study aimed to compare the diagnostic competence and triage potential of Transabdominal Ultrasonography (TAUS)—a cost-effective, first-line method—with the efficacy of the invasive method, Endoscopic Ultrasonography (EUS). Our objective was to identify specific TAUS findings that could render EUS redundant or serve as a clinical guide for referral to EUS. Methods: This prospective study included patients evaluated for suspected pancreatobiliary lesions (December 2024–September 2025). Final diagnoses (gold standard) were established using pathology, tumor board decisions, other imaging, or ≥6 months clinical follow-up. TAUS was performed by one operator blinded to clinical data. EUS was immediately performed by a different operator, blinded to TAUS results and all other clinical data. Data were grouped into normal findings, solid masses, cystic lesions, chronic pancreatitis, distal cholangiocarcinoma/ampullary tumors, and choledocholithiasis. Results: A total of 204 patients were included. TAUS sensitivity (76.5%) was significantly lower than EUS (94.6%) (p < 0.001), but both showed high specificity (TAUS: 82.9%; EUS: 88.24%). TAUS performance varied greatly by lesion type: high for solid lesions (81.8%) and chronic pancreatitis (88.9%), but markedly lower for distal common bile duct lesions/ampullary tumors (57.1%; p = 0.006). In univariate analysis, BMI (p < 0.001), lesion size (p = 0.002), MPD dilation (p = 0.001), and localization (p < 0.001) were associated with TAUS success. Lesion size (OR = 1.049, p = 0.029) was the independent predictor in the multivariate analysis. TAUS detected common bile duct dilation in obstructive cases at a high rate (95.9%) but had statistically significantly lower success in reaching a definitive diagnosis (63.3%; p < 0.001). Conclusions: While TAUS lacks the overall sensitivity of EUS, its robust detection performance for solid lesions and chronic pancreatitis suggests that it can reduce the need for further investigation in selected cases. The TAUS detection success, associated with factors like BMI and lesion size, combined with its high rate of common bile duct dilation detection, establishes a reliable triage guideline for referring patients to advanced diagnostic procedures, primarily EUS, to confirm the definitive etiology.