Objectives

-To describe the sonographic appearance of autoimmune pancreatitis (AIP) and its recurrence.

-To review the extrapancreatic manifestations of IgG-4 related disease (IgG4-RD) on ultrasound

Background

Sonography is a highly underutilized tool in the diagnosis, monitoring and post-treatment surveillance of AIP and IgG4-RD. Most cases of AIP are first investigated by sonography but often the specific findings of AIP are missed and patients are referred to CT/MR for assessment of a “malignant mass”. Multifocality is a key diagnostic feature and sonography allows the quick surveillance for other common sites of disease throughout the body when specific features of IgG4-RD are discovered on one organ. Multi-organ disease often clinches the diagnosis. Finally, ultrasound is a cost-effective method of assessing treatment effectiveness and surveillance for recurrence.

Imaging findings OR Procedure findings

Early pancreatic involvement manifests as subtle multifocal hypoechoic masses which coalesce within weeks to affect segment(s) or the entire pancreas diffusely. The pancreatic duct is strictured in areas of worse disease but shows irregular dilatation in intervening areas of milder disease. Halo sign is seen as a distinct hypoechoic rim framing the pancreas. Untreated disease often eventually shrinks and may spontaneously resolve, leaving a severely atrophic gland normalizing in echogenicity. Recurrence is easily detected as hypoechoic mass(es). Biliary disease manifests as regular circumferential thickening and can be differentiated from primary sclerosing cholangitis by a number of features. Salivary and lacrimal glands demonstrate typical sonographic patterns not detectable by CT/MR. Other sites of disease will be illustrated.

Conclusion

AIP/IgG4-RD has typical sonographic features useful for rapid diagnosis, response and surveillance.