Biliary strictures arise from diverse benign and malignant etiologies, and accurate differentiation is pivotal for prognosis and treatment selection. Conventional endoscopic retrograde cholangiopancreatography (ERCP)-based sampling (brush cytology and forceps biopsy) suffers from limited sensitivity despite high specificity, leaving a substantial proportion as indeterminate biliary strictures. Peroral cholangioscopy (POCS) enables direct intraductal visualization and targeted biopsies, thereby enhancing diagnostic yield. This review summarizes technological evolution from fiber-optic mother–baby systems to digital single-operator cholangioscopy and direct POCS, as well as the integration of image-enhanced endoscopy and emerging wide-channel scopes. Visual criteria for malignancy—tumor vessels, irregular granular or papillary/villous patterns, and friability—achieve high sensitivity and interobserver reliability with proposed classifications (Monaco, Mendoza). For cholangiocarcinoma, POCS-guided mapping biopsies precisely assess longitudinal intraepithelial tumor spread, informing R0 surgical planning. Randomized trials indicate higher or at least comparable sensitivity of POCS-guided biopsies relative to ERCP sampling, while novel forceps and larger working channels increase specimen size and reduce the number of biopsies. Artificial intelligence (AI) applied to POCS images shows promise for real-time risk stratification and improved targeting. Therapeutically, POCS guides intraductal lithotripsy with high clearance rates, and facilitates management in surgically altered anatomy in concert with endoscopic ultrasound-guided biliary drainage or transendosonographically/ guided created route procedure. Adverse events, chiefly pancreatitis and cholangitis, warrant attention to intraductal pressure control and CO2 insufflation. POCS has established an essential role in the diagnostic algorithm for biliary strictures; future advances will likely come from enhanced imaging, AI assistance, and next-generation digital cholangioscopes with larger biopsy devices.

We assessed the effectiveness of practical instruction in parasitology for undergraduates at Jichi Medical School by examining grades on a practical examination. Two hundred six second-year medical students in 1997 and 1998 (103 students in each year) were enrolled in this study. The students took written and practical examinations at the end of the program. We found that grades on the practical examination were correlated with grades on the written examination (r=0.5664; p<0.001). The discrimination index ranged from 0.23 to 0.78. The percentage of correctly identified species was significantly higher when students studied live specimens than when they used other methods (p<0.0001 in both 1997 and 1998). The highest rates of correct identification (more than 90%) were for Anisakis species larvae and Enterobius vermicularis eggs in 1997 and for Anisakis species larvae, E. vermicularis eggs, and Anopheles mosquitoes in 1998. Results of neither written nor practical examinations differed significantly between students who chose biology at the entrance examination and those who did not. Our results suggest that undergraduates would gain a better understanding of parasitology by studying live specimens.