GC constitutes a different section within choledocholithiasis, mainly when it refers to its treatment; likewise, PC and SC do not constitute a homogeneous group.

PC has been identified as an infection as part of the etiology [12]. Moreover, two significant risk factors for the recurrence of PC after endoscopic sphincterotomy have been identified: bile duct diameter ≥13 mm after stone removal and the location of the papilla at the inner edge or deep to a duodenum diverticulum [13]. Likewise, the incidence of gallstones is significantly higher in the presence of periampullary diverticula, and when considering the site and origin of gallstones, the association between diverticula and gallstones is significant in patients with PC, but not with SC [8]. In addition, it has been shown that the vast majority of patients (80%) with choledocholithiasis after cholecystectomy will present the disease within three years after surgery [1].

Contemplating GC, its characterization has been a complicated issue, and despite its low incidence, it represents a variety of implications for both, patients and health systems, which are not easy to ignore. Recently, Dai et al. published a study focused on the characteristics of biliary microbiota in patients with GC, as one more step in the knowledge of this entity [14]. GC isolated events have also been reported, as is the one published by Kumar et al. secondary to long-dwelling biliary endoprosthesis [15].

ERCP is the cornerstone for the treatment of CBD stones, being capable of treating 90% of choledocholithiasis [16]. However, there are complications related to ERCP, which seem to be more frequent in centers that perform less than 200 ERCPs per year [17,18]. One of the most serious post-ERCP complications is pancreatitis. Post-sphincterotomy bleeding has also been reported in up to 2% of cases, which is immediate in up to 30% of patients; late bleeding can occur up to two weeks after the procedure [19]. It is worth mentioning that no complications occurred during ERCP in GC in our study, differing from data reported in previous studies, despite being widely known that complications are more likely to occur in GC. The choice of sequential treatment for CBD lithos is influenced by several factors including the availability of technical expertise, instrumentation, and financial reimbursement [20]. 

In accordance with the European Society of Gastrointestinal Endoscopy (ESGE), after endoscopic biliary sphincterotomy, bile duct stones must be removed with a balloon as the first-line approach due to a 30-50% reduction of the use of mechanical lithotripsy, reserving mechanical lithotripsy in the case of failure [21]. The approach of GC in our center is mostly in accord with these guidelines, such that sphincterotomy was performed in 61% (36 patients); however, the balloon catheter was used only in 30.5% (18 patients) initially, lithotripsy being in turn considerably used forming 42.4% (25 patients). Randomized controlled trials have compared balloon over cannula techniques for small bile duct stones (<11 mm), reporting slightly better results for balloon over cannula, especially for stones <6 mm. While most cases are successfully treated with these approaches, about 10-15% of them require alternative and/or adjunctive techniques to achieve bile duct clearance. These lithos are defined as "difficult" bile duct stones, a broad category of cases that encompasses very diverse scenarios, including large, multiple, peculiarly shaped stones, located over a stricture or impacted, intrahepatic, altered distal bile duct pathway, juxtapapillary duodenal diverticulum, surgically altered anatomy, or patient-specific general conditions [22]. Hence, it is worth highlighting the lower failure rate of endoscopic complete resolution in patients with GC reported in our center (59.35%), taking into account our cut-off point of lithos ≥20 mm, contrasting with a failure rate of up to 88% reported by Corona et al., even when the stones measure between 1 and 1.5 cm [3]. In addition, the ESGE mentions that stones larger than 15 mm usually increase the difficulty of stone extraction [21].

Mechanical lithotripsy with an extraction basket is the most widely used lithotripsy technique; when this fails, extracorporeal shock wave lithotripsy could represent an alternative. The innovative techniques related to lithotripsy assisted by cholangioscopy with laser or electrohydraulic system have significantly improved the management of complex cases of choledocholithiasis; however, GC removal by direct cholangioscopy with a standard gastroscope has been reported to provide greater stability and visibility, as well as strong irrigation and suction, allowing high-quality electrohydraulic lithotripsy. This technique should only be used for giant stones >2 cm and dilated bile ducts >15 mm [17]. Li et al. reported that the clinical efficacy of SpyGlass-guided laser lithotripsy for the treatment of large CBD stones is not inferior to that of laparoscopic common bile duct exploration, and it is also less invasive [23]. Otherwise, Maydeo et al. have considered evaluating cholangioscopy-assisted lithotripsy for primary use, rather than following a failed approach, in certain scenarios [24]. Acho et al. proposed the application of robotic choledochoscopy, showing, on one hand, the tendency toward technological advancement and, on the other, the high degree of complexity in treating "difficult" bile duct stones [25].

The present study determined the existence of a significant correlation between GC and PC, a characteristic that had not been previously established. Likewise, we report the description of the endoscopic characterization of a series of 59 patients with GC (≥20 mm), which is so far the largest reported in the literature reviewed, which will contribute in some way to improve the diagnostic and/or therapeutic approach algorithm for this complex entity. 

However, there were some limitations to this study, one of them being the low incidence of GC, which translates into the difficulty of obtaining a larger sample, as well as the cross-sectional nature of our study. Hence, it would be interesting to use the data obtained here as a watershed in future prospective, randomized, controlled trials.