Objective: Patients with Autoimmune pancreatitis (AIP) frequently have lesions in the bile duct itself and show stenosis of the bile system like primary sclerosing cholangitis (PSC). Although endoscopic retrograde cholangiopancreatography can demonstrate stenosis of the bile duct, and ultrasonography (US) can indicate thickening of the bile duct wall, no detailed study has evaluated the US findings of bile duct lesions in AIP (sclerosing cholangitis with AIP: SC-AIP).
Methods: Between 1986 and 2008, 42 patients of AIP and 14 patients of PSC were treated at our hospital. Bile duct lesion was recognized on US in 35.7% (15/42) of AIP patients. We retrospectively analyzed the clinical course, imaging findings, mainly US, of SC-AIP, and the difference between SC-AIP and PSC.
Results: We could divide the SC-AIP cases into two types according to the US findings of bile duct wall thickening: (1) three-layered type: marked wall thickening apparent on US as high-low-high echo of the bile duct wall and (2) parenchymal-echo type: thickened wall that occupies the entire lumen of the bile duct with appearances of parenchymal echo in the bile duct. The thickened wall of SC-AIP were lower echogenic than that of PSC, and mucosal surface of SC-AIP was smooth in 73.3%, whereas PSC was mostly irregular. These data suggest that echogenicity of thickened wall and irregularity of mucosal surface could become one of discrimination between SC-AIP and PSC.
Conclusion: Ultrasonography is a useful tool in detecting biliary tract lesions in AIP and discrimination between SC-AIP and PSC.