What are the sensitivity and specificity of ERCP and imaging findings for diagnosing biliary versus pancreatic fluke infections in clinical series?
Executive summary
Published clinical literature does not include well-powered series that report numeric sensitivity and specificity of ERCP or cross-sectional imaging specifically for biliary versus pancreatic fluke infections; available evidence is composed mainly of case reports and extrapolation from studies of biliary and pancreatic duct pathology where MRCP, EUS and ERCP have high accuracy for stones and strictures (but not parasitoses) [1] [2] [3]. ERCP retains a unique therapeutic–diagnostic role because it can directly visualize and extract motile flukes, giving essentially pathognomonic confirmation when the parasite is seen, while noninvasive imaging can suggest obstruction but frequently cannot distinguish fluke infection from stones or malignancy [1] [4] [5].
1. ERCP: the “see it, pull it out” gold-standard for confirmed biliary fluke—high specificity but unknown sensitivity
Case-based literature and expert summaries emphasize that when an adult biliary fluke is directly visualized and removed at ERCP, the diagnosis is definitive—endoscopic extraction is repeatedly reported as both diagnostic and therapeutic in biliary fascioliasis and other liver-fluke infections [1] [6]. That practical reality implies very high specificity for ERCP in confirmed-fluke cases (visualized organism = true positive) [1]. However, no clinical series in the provided sources report a population-based sensitivity for ERCP in detecting flukes, and sensitivity will be limited by parasite location (intrahepatic/proximal ducts may be missed), intermittent ductal migration, and procedural factors; therefore numeric sensitivity for fluke detection is not available in the reviewed literature [1] [4].
2. MRCP, CT and ultrasound: accurate for obstruction, poor at etiologic discrimination in fluke disease
Systematic comparisons of MRCP versus ERCP in biliary obstruction show MRCP can have very high sensitivity and specificity for strictures and stones in general cohorts—some series report near-100% sensitivity and >98% specificity for stricture detection versus ERCP as reference [2] [3] [7]. Those figures demonstrate MRCP’s power to detect anatomic obstruction but do not establish MRCP’s ability to identify flukes specifically: imaging findings of ductal filling defects or biliary wall irregularity caused by flukes can mimic stones or cholangiocarcinoma, and reports warn of misdiagnosis in non‑endemic settings [1]. Therefore MRCP/CT/US are sensitive for identifying obstruction but their specificity for parasitic etiology is unreported in clinical series of fluke disease within the available sources [2] [3] [1].
3. EUS and intraductal ultrasound (IDUS): added sensitivity for mobile or proximal organisms in case reports
Endoscopic ultrasound (EUS) and intraductal ultrasonography (IDUS) performed adjunctively during ERCP provide higher-resolution, real-time cross-sectional views of ducts and have been documented to detect mobile worms in extrahepatic ducts and proximal bile ducts in single-case reports; IDUS aided detection and immediate treatment in one published fascioliasis case [1]. Those reports suggest EUS/IDUS may increase diagnostic yield in selected patients, but there are no clinical series in the provided material that quantify sensitivity or specificity of EUS/IDUS for fluke infections [1].
4. Comparative accuracy for pancreatic flukes: data absent; pancreatic duct involvement is rare and undocumented in series
None of the provided sources offer population-level sensitivity or specificity estimates for imaging or ERCP in diagnosing pancreatic fluke infections. Pancreatic duct parasitism is uncommon and most referenced studies concern biliary tree disease, so no direct diagnostic performance metrics for pancreatic flukes can be extracted from the available literature [1] [8].
5. Clinical and methodological caveats—risk, selection bias and diagnostic intent
ERCP is increasingly reserved for therapeutic procedures or targeted diagnostics because noninvasive modalities have comparable sensitivity/specificity for many ductal problems and because ERCP carries known risks including pancreatitis, bleeding and perforation [9] [4] [10]. Many diagnostic accuracy studies cited used ERCP as a gold standard for structural lesions (stones/strictures), a methodological choice that does not translate into robust sensitivity/specificity estimates for rare parasitic etiologies; available fluke literature is dominated by case reports and therefore subject to selection and publication bias [2] [5].
Conclusion: what can be stated with confidence and what cannot
It is established that ERCP with direct visualization/removal of a fluke provides essentially definitive (highly specific) diagnosis and immediate therapy, and that MRCP/EUS/CT are sensitive for detecting ductal obstruction but lack validated specificity for distinguishing flukes from stones or tumors in clinical series; however, no reliable numeric sensitivity or specificity values for ERCP or imaging specifically for biliary or pancreatic fluke infections are reported in the sources supplied, and population-level estimates remain unavailable [1] [2] [3].