Introduction
Autoimmune pancreatitis (AIP) is a rare disease that can be diagnosed, according to the International Consensus Diagnostic Criteria (ICDC). Contrast-enhanced MRI with MRCP has now largely replaced other imaging techniques and ERCP for the assessment of ductal morphology in AIP. A number of MRI-criteria have been proposed, but due to the rarity of the disease the diagnostic imaging criteria have not yet been systematically validated. Aim of the study is to review and optimize the MR-morphologic diagnostic criteria for AIP in terms of specificity and sensitivity in the diagnosis and differential diagnosis of the pancreaticobiliary system.
Aims & Methods
We analyzed retrospectively hundred-fiftysix (n=156) high-quality MRIs: AIP n=56, chronic pancreatitis (CP) n=25, pancreatic cancer (PDAC) n=25, primary sclerosing cholangitis (PSC) n=25, Non-HPB subjects n=25. The MRI reading was conducted in a blinded fashion, using defined criteria by at least two radiological experts. The statistical analysis was performed by means of Proportion test, Chi-square test or Fisher’s exact test, One-way ANOVA and Cohen’s Kappa Statistic of the level of agreement.
Results
The level of agreement between two readers was moderate to substantial agreement (κ 0.23-0.85). Sausage-like enlargment (Reader 1: Sens 30.91%, Spec 98.98%, NPV 71.85%, accuracy 74.51%; Reader 2: Sens 26.79%, Spec 98.00%, NPV 70.50%, accuracy 72.43%), restricted diffusion (Reader 1: Sens 47.83%, Spec 89.29%, NPV 75.76%, accuracy 74.51%; Reader 2: Sens 56.86%, Spec 73.26%, NPV 74.12%, accuracy 72.30%), delayed enhancement in the venous phase (Reader 1: Sens 8.70%, Spec 83.15%, NPV 63.79%, accuracy 74.10%; Reader 2: Sens 32.61%, Spec 79.31%, NPV 69.00%, accuracy 75.19%), the icicle sign (Reader 1: Sens 10.91%, Spec 100%, NPV 66.67%, accuracy 65.30%; Reader 2: Sens 37.50%, Spec 91.00%, NPV 72.22%, accuracy 71.79%) and hyperenhancement of ductal wall (Reader 1: Sens 14.29%, Spec 96.67%, NPV 67.44%, accuracy 71.90%; Reader 2: Sens 8.51%, Spec 95.45%, NPV 66.14%, accuracy 74.10%) show a good accuracy distinguishing AIP from controls. Apparent diffusion coefficient (ADC) was significantly different between AIP, PDAC and CP (ANOVA). The area under the receiver operating characteristic curve (AUROC) was 0.85 (CI 0.73 – 0.97) and 0.68 (CI 0.51 – 0.85) respectively for CP and PDAC.
Conclusion
Our study showed that the Sausage-like enlargment, restricted diffusion, delayed enhancement in the venous phase, the icicle sign and hyperenhancement of ductal wall show a good accuracy distinguishing AIP from controls.
