Endoscopic ultrasonographic study of autoimmune pancreatitis and the effect of steroid therapy

Recently, endoscopic ultrasonography (EUS) has been used for the diagnosis of chronic pancreatitis (CP); however, EUS diagnosis of autoimmune pancreatitis (AIP) varies among different researchers. We investigated EUS findings in AIP and retrospectively analyzed them before and after steroid therapy.

The subjects were 32 patients with AIP and the EUS images of the pancreatic parenchyma were evaluated with reference to the Sahai criteria. Patients' background factors detected by EUS were analyzed statistically. Peroral steroid was given to 23 of the 32 patients. EUS was also performed 2 weeks after the initiation of therapy in 14 of the 23 patients, and the changes in EUS were investigated. Microscope images were compared with EUS images in one patient who underwent surgical resection.

EUS results included hyperechoic strands in 26 (81.3%) and lobularity in 17 (53.1%) patients. The patients' background factors included the presence of splenic and/or portal vein occlusion or narrowing around the pancreas in patients who had neither hyperechoic strands nor lobularity (p = 0.002, p = 0.004). The numbers of EUS findings before versus after steroid therapy were 11 versus 5 for hyperechoic strands and 7 versus 2 for lobularity. Microscope images showed the coexistence of relatively well-maintained lobular structures of pancreatic acini and almost complete loss of such structures.

EUS findings in AIP were similar to those in early-stage CP, and hyperechoic strands and lobularity seem to suggest a condition under which the histology of lobular structures of the pancreatic acini is relatively well-maintained. EUS results had improved within about 2 weeks of steroid therapy.