Sa1299 HOW CAN ISOLATED PROXIMAL-TYPE IGG4-RELATED SCLEROSING CHOLANGITIS BE DIAGNOSED?

Abstract

In rare cases, IgG4-related sclerosing cholangitis (IgG4-SC) presents as isolated proximal-type sclerosing cholangitis (i-SC), making diagnosis challenging and resulting in resection in a majority of cases. To clarify the clinical differences between IgG4-SC with and without autoimmune pancreatitis (AIP) and to reveal tips for ruling out malignancy. First, the serum IgG4 level, CA19-9 level, CT findings (nodular lesion), cholangiography findings (apple core appearance; symmetrical smooth long stricture extended upper bile duct), endosonographic features (continuous symmetric mucosal lesion to the hilar part or CSML), endoscopic biopsy results, treatment, relapse, and survival were compared between 9 patients with i-SC and 34 patients with IgG4-SC associated with AIP. Second, the above-mentioned factors were also compared between the i-SC patients and 47 patients with Klatskin tumor. Regarding the differentiation of i-SC and IgG4-SC with AIP, the serum IgG4 level was 338 mg/dL in the i-SC group and 680 mg/dL in the IgG4-SC with AIP group (P < 0.05), and nodular lesions on CT images and an apple core appearance on cholangiography images were significantly more common in the i-SC group (P < 0.01). Endoscopic histopathology specimens from the bile duct were not diagnostic for IgG4-SC. An ampulla biopsy was helpful in the diagnosis of 80% (4/5) of the patients in the i-SC group and 82.3% (14/17) of the patients in the IgG4-SC with AIP group. Resection was performed in 3 patients with i-SC and 3 patients with AIP-SC based on a suspicion of malignancy. Five patients with i-SC underwent a steroid trial. The non-relapse rates were (NRR; i-SC vs. AIP-SC) 100% vs. 79% at 1 year, 100% vs. 53.8% at 3 years, and 66.7% vs. 25.8% at 5 years. The relapse rates were significantly higher in the IgG4-SC with AIP group than in the i-SC group (log rank, P = 0.046). For a differential diagnosis between i-SC and Klatskin tumor, the serum IgG4 level was significantly higher in the i-SC group and the CA19-9 level was higher in the Klatskin tumor group (P < 0.01). The length of the stricture was significantly longer in the Klatskin tumor group (P < 0.01). Complete obstruction was recognized significantly more often in the Klatskin tumor group (P < 0.01). An apple core appearance and CSML were noted significantly more often in the i-SC group (P < 0.01). i-SC presents as a nodular lesion with an apple core appearance mimicking a Klatskin tumor. i-SC exhibits atypical features of IgG4-SC, and serum markers are helpful for differentiating from cancer. A short stricture length without complete obstruction and CSML might be clues for a diagnosis of i-SC. However, once a diagnosis of i-SC has been made, this disease entity is likely to have a more favorable prognosis than IgG4-SC with AIP.