Differential diagnosis between benign and malignant localized stenosis of the main pancreatic duct by intraductal ultrasound of the pancreas

Objectives: Our objectives in this study were to differentiate between pancreatic cancer (PC) and chronic pancreatitis (CP) in cases with localized stenosis of the main pancreatic duct (MPD) by an intraductal ultrasound (IDUS) probe which were detected on pancreatogram. Methods: We inserted the IDUS probe (30 MHz) into the MPD in all cases and scanned the stenotic site in 23 of 26 cases (88.5%) in vivo. In all 26 patients, the stenotic site was surgically resected, and IDUS scanning was also performed on the resected specimens. Findings from IDUS were compared with those from histology. The diagnostic ability of IDUS was compared with that of endoscopic ultrasonography (EUS), computed tomography (CT), and endoscopic retrograde pancreatography (ERP). Results: The IDUS images of localized stenosis were classified into two types: type I showed an echo-rich area surrounded by an echo-poor margin and was found in 14 PC patients and one CP patient; type II showed a ring-like echolucent band surrounded by a fine reticular pattern and was found in 11 CP. Therefore, we considered that type I tended to be characteristic of PC, whereas type II tended to be characteristic of CP. Sensitivities of EUS, CT, ERP, and IDUS in diagnosing PC were 92.9% (13/14), 64.3% (9/14), 85.7% (12/14), and 100% (14/14), respectively. Specificities of EUS, CT, ERP, and IDUS were 58.3% (7/12), 66.7% (8/12), 66.7% (8/12), and 91.7% (11/12), respectively. Conclusions: IDUS examination might be useful in the diagnosis of patients with localized stenosis of the MPD, but its precise role in the diagnostic work-up of patients with pancreatic diseases remains to be determined by further studies.