Pancreatic and extra-pancreatic transabdominal ultrasound findings of type 1 autoimmune pancreatitis.

Background: Autoimmune pancreatitis (AIP) is an important manifestation of immunoglobulin G4 (IgG4)-related diseases with multi-organ involvement. This study sought to retrospectively analyze pancreatic and extra-pancreatic ultrasonography findings in patients with AIP, and to determine the value of transabdominal ultrasound (TUS) in the diagnosis of AIP.

Methods: In total, 19 patients with type 1 AIP (12 males and seven females; mean age: 52.84±15.33 years; range: 18-83 years) underwent ultrasound examinations of the pancreas, peripancreatic lymph nodes, gall bladder, bile ducts, retroperitoneal, kidneys, and submandibular and lacrimal glands.

Results: According to the distribution of the lesions, the pancreatic images were categorized into the following three types: diffuse (n=9), segmental (n=5), and focal (n=5). These images showed diffuse, segmental, or focal enlargement of the pancreas with hypoechoic parenchyma. Contrast-enhanced ultrasound (CEUS) revealed hypoenhancement in the diffuse type. A thick capsule-like echo surrounding the lesion was observed in 12 patients. The main pancreatic duct was dilated in eight patients. No calcification was detected in any of the 19 patients. Peripancreatic lymph nodes were identified in four patients. Vascularity was found in four of eight patients for whom color Doppler flow images (CDFIs) of the pancreas were available. The intrahepatic and common bile ducts were dilated in 11 patients. The gallbladder was found to be involved in 13 patients. Except for one patient with hydronephrosis due to retroperitoneal fibrosis, no abnormalities were observed in the kidneys. Retroperitoneal fibrosis was found in one patient. Among the 12 patients for whom data were available, parenchymal inhomogeneity was observed in the parotid glands of three patients, the submandibular glands of five patients, and the lacrimal glands of eight patients.

Conclusions: Ultrasonography is valuable in the diagnosis of AIP. In addition to TUS, other ultrasound technologies, such as CEUS and TUS-guided biopsy, could also play a crucial role in the diagnosis of AIP.