The ultrasound and contrast-enhanced ultrasound characteristics of IgG4-related cholangitis: compared with cholangiocarcinoma.

BACKGROUND: IgG4-related cholangitis (IgG4-SC) is often difficult to differentiate from cholangiocarcinoma (CCA) due to similar clinical and imaging presentations, yet their management and prognosis differ drastically. Accurate non-invasive distinction remains a significant clinical challenge. AIM: This study aimed to identify and compare the characteristic features of IgG4-SC and CCA on conventional ultrasound (US) and contrast-enhanced ultrasound (CEUS) to establish reliable imaging discriminators. METHODS: We retrospectively analyzed clinical and imaging data from 14 patients with IgG4-SC and 26 with CCA. Two blinded physicians independently reviewed US and CEUS images to assess lesion characteristics, bile duct lumen visibility, wall thickening, and enhancement patterns. Statistical comparisons were performed using appropriate tests. RESULTS: On conventional US, a preserved bile duct lumen within the thickened segment was significantly more frequent in IgG4-SC (10/14, 71.4%) than in CCA (1/26, 3.8%; P < 0.001). Concomitant lesions in other organs were also more common in IgG4-SC (50% vs. 3.8%, P = 0.001). On CEUS, arterial-phase hyper-enhancement was observed in 95.8% of CCA lesions but only in 50.0% of IgG4-SC lesions (P = 0.009), with the latter showing more variable (hypo-/iso-) enhancement. CONCLUSION: The combination of a preserved bile duct lumen on conventional US and a lower frequency of arterial hyper-enhancement on CEUS provides key imaging clues to differentiate IgG4-SC from CCA. These features, alongside assessment for other organ involvement, may improve diagnostic confidence and guide appropriate clinical management. However, given the exploratory nature of this small-sample study, these findings require validation in larger prospective cohorts.