Multidetector row computed tomography pattern in differential diagnosis of diffuse autoimmune pancreatitis and non necrotizing acute pancreatitis at clinical onset

Purpose: The aim was to retrospectively evaluate the utility of Multidetector Row Computed Tomography (MDCT), in differentiating Diffuse Autoimmune Pancreatitis (DAIP) from Non Necrotizing Acute Pancreatitis (NNAP) at clinical onset. Methods and Materials: We enrolled 36 consecutive Patients DAIP (14) or NNAP (22) affected. Inclusion criteria were first episode of DAIP or NNAP diagnoses and abdomen MDCT examination within 48-72 hours at the clinical onset. Qualitative analysis included the evaluation of pancreatic density in all MDCT phases, stranding, retroperitoneal fluid film, capsule like rim enhancement and pleural effusion. In quantitative analysis we measured pancreatic thickness and density in all phases using freehand ROI in axial and 64 slices multiplanar reconstruction images. We assessed the vascularization behaviour using the Relative Enhancement Rate (RER) across all phases. Results: Compared to the spleen, pancreas resulted hypodense in 92.9% of DAIP Patients with progressive retention of contrast media and isodense in 90.9% of NNAP Patients with progressive wash out. Only NNAP Patients presented peripancreatic stranding and retroperitoneal fluid film. Qualitative enhancement data were confirmed by quantitative analysis of pancreatic density and vascularization behaviour assessed using the RER. Conclusion: MDCT is a useful technique for differentiating DAIP from NNAP at clinical onset. The retroperitoneal findings of peripancreatic stranding and retroperitoneal fluid film, characteristic of NNAP, and late-phase peripheral rim enhancement, characteristic of DAIP, provide qualitative clues to the differentiation. A quantitative study of contrast enhancement patterns, particularly by considering the Relative Enhancement Rate parameters presented in this work, can also assist in the differential diagnoses.