The Role of Endoscopic Ultrasound and Ancillary Techniques in the Diagnosis of Autoimmune Pancreatitis: A Comprehensive Review

Abstract

Autoimmune pancreatitis (AIP) is a unique form of chronic pancreatitis with a multifactorial pathogenesis. Historically, it has been classified as type 1 and type 2, according to its clinical and histological features. The diagnosis of AIP is challenging and relies on a combination of clinical, histopathologic, serologic, and imaging characteristics. In the available guidelines, the imaging hallmarks of AIP are based on cross-sectional imaging and cholangiopancreatography retrograde endoscopic findings. Endoscopic ultrasound (EUS) is generally used for pancreatic tissue acquisition to rule out pancreatic cancer and diagnose AIP with limited accuracy. Several papers reported the reliability of EUS for providing informative morphologic features of AIP. Nowadays, the improvement in the resolution of EUS conventional images and the development of new ancillary technologies have further increased the diagnostic yield of EUS: contrast-enhanced EUS and EUS elastography are non-invasive and real-time techniques that strongly support the diagnosis and management of pancreatic diseases. In this review article, we will present the role of conventional EUS and ancillary diagnostic techniques in the diagnosis of AIP to support clinicians and endosonographers in managing this condition.

Keywords: autoimmune pancreatitis; chronic pancreatitis; contrast-enhanced endoscopic ultrasound; elastography; endoscopic ultrasound; fine-needle aspiration; fine-needle biopsy; pancreatic cancer; time–intensity curves.

Figure 1

Endoscopic ultrasonography in autoimmune pancreatitis. (a) Hypoechoic rim around pancreatic parenchyma (arrows). (b) Visible unobstructed main pancreatic duct (MPD) with thickened wall: “duct-penetrating sign”. (c) Thickened wall of common bile duct (CBD) with 3-layer-type appearance.

Figure 2

Contrast-enhanced harmonic EUS of focal-type autoimmune pancreatitis. (a) Hypoechoic focal enlargement of pancreatic head (B mode). (b) Second harmonic imaging before contrast. (c) Homogeneous hyperenhancement in arterial phase (15 s). (d) Homogeneous isoenhancement in late phase (35 s).