Diagnostic Accuracy of Transabdominal Ultrasound (TAUS) Compared to Endoscopic Ultrasound (EUS) in the Diagnosis of Gallbladder and Biliary Diseases

Abstract

Background: Transabdominal ultrasound (TAUS) is the first-line imaging modality for gallbladder (GB) and biliary diseases, however, its diagnostic performance may decline for microlithiasis, and distal biliary and pancreatic lesions where endoscopic ultrasound (EUS) could superior.
Aim: To compare the diagnostic accuracy of TAUS versus EUS in the detection and characterization of GB and biliary lesions.
Patients and Methods: This cross-sectional observational study included 201 adults (mean age 47.8 ± 11.9 years; 53.2% female) evaluated with TAUS and EUS (single expert operator for each modality). Diagnostic indices (sensitivity/specificity/PPV/NPV/accuracy) and agreement (kappa) were calculated using EUS as reference.
Results: Transabdominal ultrasonography (TAUS) demonstrated high diagnostic performance for common gallbladder (GB) pathology, with a sensitivity of 75% and specificity of 99.5% (κ = 0.817) for overall GB stones. For stones measuring 5–10 mm, sensitivity was 95.1% (κ = 0.969), while stones >10 mm were detected with 100% sensitivity (κ = 0.884). The sensitivity for GB sludge was 78.6% (κ = 0.843). TAUS demonstrated perfect diagnostic concordance for common bile duct (CBD) dilatation (κ = 1) and high sensitivity for intrahepatic biliary radicle dilatation (89.3%; κ = 0.914).
In contrast, TAUS demonstrated markedly limited sensitivity for lesions that are frequently occult on conventional ultrasonography, including GB microlithiasis (4.35%), CBD stones (9.09%; κ = 0.159), and pancreatic head masses (11.76%; κ = 0.164). Among patients with CBD dilatation (n = 42), TAUS identified an underlying etiology in only 28.5% of cases, compared with 85.7% with EUS (P < 0.001). EUS also demonstrated significantly higher detection rates for CBD stones (26.1% vs. 2.4%, P = 0.002) and pancreatic head masses (23.8% vs. 7.1%, P = 0.035).
Conclusion: TAUS provides reliable diagnostic assessment of GB wall thickening, gallstones ≥5 mm, biliary sludge, and biliary ductal dilatation. However, EUS substantially enhances the detection of small gallstones and microlithiasis, CBD stones, and pancreatic lesions, while providing superior etiological delineation in patients with otherwise unexplained CBD dilatation.