MRCP Vs ERCP: A Comparative Study in Diagnosis of Common Bile Duct Stones

Abstract

Background: Because it is a noninvasive method, without complications, the magnetic resonance cholangiography (MRCP) is going to reliably replace ERCP in the diagnosis of pancreato-biliary diseases. Although many studies documented a high sensitivity and specificity of MRCP, its ability in detecting microlithiasis (< 5 mm in diameter) of common bile duct (CBD), responsible for acute biliary pancreatitis, is still controversial. Aim: to evaluate sensitivity, specificity, diagnostic accuracy, positive predictive value (PPV) and negative predictive value (NPV) of MRCP in diagnosis of choledocolithiasis using ERCP + endoscopic sphincterotomy (ES) as the gold standard. Patients and methods: 123 individuals, suspected for lithiasis of CBD were prospectively enrolled in the study. Clinical findings were: jaundice, fever, abdominal and/or biliary pain, weight loss with altered cholestatic enzymes (ALP > 270; Î3-GT > 50 UI/l). Patients underwent upper abdominal ultrasonography (US), then MRCP and, within 72 h, diagnostic and/or operative ERCP. All patients signed an informed consent. The statistical analysis was based on the report of true positives and negatives, false positives and negatives. Results:106/123 patients completed the study. MRCP diagnosed lithiasis of CBD in 73; did not document stones in 33. ERCP confirmed the presence of lithiasis in 66/73 pts who were submitted to ES. Seven were not found to have stones after ES. Among 33 negative pts, ERCP documented stones in 9: in 4 only after ES (it was performed according to clinico-biochemical data and to CBD dilation, though ERCP did not identify stones). The stones were 2-3 mm. In 24/33 patients negative at MRCP, ERCP confirmed this response:10/24 were submitted to ES. ES was not performed in 14/24 subjects, without CBD dilation and/or cholestasis. After a 27.8 months follow-up (range: 4-54), 8/14 remained asymptomatic, 6 underwent laparoscopic cholecystectomy without finding of CBD stones at the intra-operative cholangiography. The sensitivity, specificity, diagnostic accuracy, PPV and NPV of MRCP were: 88%, 77%, 85%, 90%, 73%. Conclusions: as MRCP has still a limitation in the diagnosis of small stones, missed at US, it leaves unrisolved the question of which patient is candidate to ERCP/ES. The recognition of microlithiasis should refer to other imaging techniques preliminar to ERCP (e.g. EUS) though their limited availability makes until now MRCP a method of choice in the diagnosis of biliary disease.