Diagnostic efficacy of a brand-new endoscopic ultrasound processor for early-stage chronic pancreatitis.

Abstract

Diagnosing early-stage chronic pancreatitis (early-CP) is challenging because obtaining pancreas tissue samples to confirm clinical diagnosis is almost impossible. Recently, some features of pancreas parenchyma that can be visualized solely using endoscopic ultrasound (EUS) have been recognized as reflecting very slight parenchymal changes of early-CP.1 However, typical findings that reflect parenchyma changes are trivial and delicate. Therefore, definitive diagnosis of early-CP is sometimes difficult to accomplish solely through findings obtained using conventional EUS. New EUS processor (UM-ME2; Olympus Medical Systems Corp., Tokyo, Japan) can serve both tissue harmonic echo (THE) penetration mode and THE resolution mode. Both shallow and deep areas can be depicted more clearly using THE penetration mode than using B-mode (Fig. 1a,b). However, EUS images produced using THE resolution mode are extremely clear and sharp in the area of interest, whereas images within the unfocused area become dim (Fig. 1c). To diagnose early-CP, the Japanese clinical diagnostic criteria2 require slight abnormalities in pancreatic parenchyma and pancreatic duct on EUS. These new THE modes can reveal details of abnormalities of early-CP. (a) B-mode shows lobularities in pancreas parenchyma. (b) Image using tissue harmonic echo (THE) penetrate mode shows the lobularities clearer than B-mode image. (c) Lobularities in focused area by using THE resolution mode are very clear and sharp. However, images within unfocused area become dim. Moreover, UM-ME2 can immediately facilitate elastography during EUS procedures. Elastography can analyze tissue stiffness during scanning of pancreas parenchyma using EUS. Using elastography, fibrous change/stiffness in the pancreas parenchyma can be visualized as an inhomogeneous echo pattern with mixing of colors.3 In elastography, normal pancreas parenchyma is visualized as a homogeneous green pattern (Fig. 2a). However, in cases of CP, which has some hyperechoic abnormalities (foci, stranding and lobularity), elastography shows an inhomogeneous mosaic echo pattern with mixing of colors: blue, green, and yellow (Fig. 2b). This mosaic pattern is thought to reflect parenchymal changes including fibrosis and calcification in CP. It is considered that EUS-elastography is useful for the objective diagnosis of early-CP. (a) B-mode image using UM-ME2 (Olympus Medical Systems Corp., Tokyo, Japan) shows normal pancreas parenchyma. The normal pancreas parenchyma shows a homogeneous green pattern in elastography. (b) B-mode image shows hyperechoic strands and lobularities in pancreas parenchyma. There is no calcification and dilated/irregular pancreatic duct. These findings indicate early-stage chronic pancreatitis. Elastography shows an inhomogeneous mosaic echo pattern with mixing of colors; blue, green and yellow. This mosaic pattern is thought to reflect parenchymal changes in chronic pancreatitis. New THE modes and elastography provided by UM-ME2 might contribute to a definite diagnosis of early-CP. Authors declare no conflict of interests for this article.