Sa1299 Magnetic Resonance Cholangio-Pancreatography (MRCP) Has a High Negative Predictive Value in Patients Suspected to Have Choledocholithiasis

Abstract

Background: Choledocholithiasis (CDL) is a common and potentially severe form of gallstone disease. Magnetic resonance cholangio-pancreatography (MRCP) is an increasingly used imaging modality in patients with a suspicion of CDL but limited data exist of the diagnostic accuracy in clinical practice. We aimed to assess its diagnostic performance in patients with a suspicion of CDL. Methods: A retrospective study of patients who were suspected to have CDL that had MRCP in a University Hospital in consecutive patients investigated during one year at this single Institution. Patients with other indications than gallstone disease for MRCP such as malignancy were excluded. Information was obtained on age, gender, liver tests, lipase/amylase and number of patients that underwent ERCP following the MRCP and the outcome of ERCP. Results: A total of 179 patients (females 63%, median age 56 years) had an MRCP due to suspected CDL. MRCP showed stones in the common bile duct (CBD) in 49 patients and none in 130. Overall 55 patients underwent ERCP after an abnormal MRCP (stones and/or dilated ducts) and 39 of them had documented stones (71%). Only 1/49 (2%) patient had a stone demonstrated on ERCP followed by a normal MRCP. None of the other patients with a normal MRCP had symptoms or signs of choledocholithiasis or were hospitalized for gallstone disease during at least 6 months after the normal MRCP. Patients with stones in the CBD on MRCP had higher values of bilirubin (45 μmol/L vs. 19, p=0.001), GGT (458 vs. 286, p=0.04) and AST (214 vs. 130, p=0.03) than those without stones, whereas other blood tests did not differ between the two groups. A total of 37/49 (76%) of patients with CBD stones had elevated bilirubin vs. 52/130 (40%) in those without CBD stones (p,0.05). Overall 46 patients were diagnosed with pancreatitis ( .threefold elevation of lipase) and among those only 9/49 (18%) had stones in the CBD on ERCP and/ or MRCP. The patients diagnosed with gallstones demonstrated in the CBD had a median value of lipase 4068 (981-9332) vs. 4400 (1192-11851) in those without stones (NS). Conclusion: MRCP in patients suspected to have stones in CBD has a very high negative predictive value and can prevent unnecessary ERCPs. Elevation of bilirubin, GGT and AST along with stones and dilated ducts shown on MRCP is a strong indicator of the presence of stones in the CBD. Gallstone pancreatitis is as common in those with and without stones in the CBD, suggesting that in surprisingly many patients the elevation in lipase is associated with spontaneous passage of stones through the CBD.