Dual-frequency intraductal ultrasonography: a breakthrough in biliopancreatic imaging during endoscopic retrograde cholangiopancreatography

Intraductal ultrasonography (IDUS) is a reliable procedure for evaluating the biliopancreatic duct during endoscopic retrograde cholangiopancreatography (ERCP) [1] [2]; however, conventional high frequency IDUS is limited by its penetration depth [3]. This case highlights a novel dual-frequency IDUS probe that overcomes this limitation ([Fig. 1]; [Video 1]).

Fig. 1 Photograph of the dual-frequency intraductal ultrasonography probe showing: a the probe, which features two frequencies (20 MHz and 7.5 MHz) that are switchable via the main engine; b the probe tip, which has an outer diameter of 2.5 mm.

A novel dual-frequency intraductal ultrasonography probe is used to evaluate biliopancreatic disease during endoscopic retrograde cholangiopancreatography.Video 1

A 60-year-old woman was referred to our hospital with jaundice. Magnetic resonance imaging (MRI) revealed a pancreatic head mass with distal bile duct obstruction ([Fig. 2]). Laboratory tests showed she had a serum total bilirubin of 330 μmol/L and a CA19-9 of 146 U/mL, and a preliminary clinical diagnosis of pancreatic head cancer was made.

Fig. 2 Enhanced magnetic resonance imaging and magnetic resonance cholangiopancreatography (MRCP) images showing: a in arterial phase, mild enhancement of the pancreatic head lesion; b in portal phase, progressive enhancement; c on MRCP, a distal bile duct stricture with upstream bile duct dilatation and slight pancreatic duct dilatation.

Endoscopic retrograde cholangiography (ERC) revealed a defect in the distal bile duct on contrast injection. To determine the nature of this biliary stricture, a novel IDUS probe with dual frequencies of 20 MHz and 7.5 MHz (DP-27, 7.5+20 MHz; Innermed, Shenzhen, China) was advanced over guidewires into the pancreatic duct and bile duct, which were scanned using the pull-back method. Using the 20-MHz frequency, the IDUS scan showed the pancreatic duct and proximal surrounding structures ([Fig. 3] a). On switching to 7.5 MHz, the far-field resolution significantly improved, allowing visualization of the complete pancreatic contour and parenchyma ([Fig. 3] b). The pancreatic head appeared as a heterogeneous hypoechoic region without any evident tumorous lesions. A subsequent 20-MHz scan of the intrapancreatic bile duct revealed a circular symmetrical wall thickening, with a smooth outer margin ([Fig. 3] c). A switch to 7.5 MHz confirmed no evidence of an extrinsic lesion causing compression ([Fig. 3] d).

Fig. 3 Images during dual-frequency intraductal ultrasonography (IDUS) showing; a the appearance on 20-MHz IDUS of the pancreatic duct; b on 7.5-MHz IDUS, a high resolution image of the pancreatic parenchyma; c on 20-MHz IDUS, intrapancreatic biliary wall thickening; d on 7.5-MHz IDUS, detailed periductal structural information.

The IDUS images were therefore used to make a diagnosis of autoimmune pancreatitis and IgG4-related sclerosing cholangitis (IgG4-SC), which was confirmed by finding an elevated serum IgG4 level and on endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA). Following glucocorticoid therapy, the patient’s symptoms resolved, and imaging showed significant improvement. This dual-frequency IDUS technology offers enhanced diagnostic capability and can be seamlessly integrated into routine ERCP procedures, significantly reducing diagnostic delays and improving patient management.

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Conflict of Interest

The authors declare that they have no conflict of interest.

Acknowledgement

We express our sincere gratitude to Professor He for his meticulous work ethic, invaluable suggestions, and insightful discussions. We also extend our thanks to Nurse Liu Pingping for her ongoing collaboration and technical assistance throughout our study.

• References

• 1 Chen L, Lu Y, Wu JC. et al. Diagnostic utility of endoscopic retrograde cholangiography/intraductal ultrasound (ERC/IDUS) in distinguishing malignant from benign bile duct obstruction. Dig Dis Sci 2016; 61: 610-617
• 2 Naitoh I, Nakazawa T. Endoscopic retrograde cholangiopancreatography and intraductal ultrasonography in the diagnosis of autoimmune pancreatitis and IgG4-related sclerosing cholangitis. J Med Ultrason 2021; 48: 573-580
• 3 Cheon YK. Intraductal ultrasonography for biliary strictures. Clin Endosc 2023; 56: 164-168

Publication History

Article published online:
06 May 2025