**3. Pancreatic ductal stones**

Unlike biliary stones, most pancreatic ductal stones are calcified and radiopaque. Stone prevalence increases during CP. In a multicenter study, 62% of 879 patients with CP reported calcified pancreatic stones. Heavy smokers (≥20 cigarettes/day), heavy drinkers (alcohol consumption of >80 g/day), and men have more pancreatic ductal stones than others [13].

Endoscopy, pancreatic sphincterotomy, and basket or balloon dilation allow stone extraction in only 9% of the patients. It is associated with stones of >10 mm, stone impaction, and a diffuse location [14]. Moreover, pancreatic mechanical lithotripsy has a threefold higher complication rate than biliary mechanical lithotripsy. These complications include trapped or broken baskets, traction wire fractures, and pancreatic ductal leak [15]. Furthermore, extracorporeal shock wave lithotripsy (ESWL) allowed successful pancreatic stone clearance in >80% of patients after failed stone extraction with endoscopy [16]. Therefore, primary endoscopy is reserved for selected patients with radiolucent stones or stones of <5 mm in size that are challenging to target with ESWL.

ESWL is a widely accepted treatment modality for radiopaque MPD stones when the MPD stone is larger than 5 mm and located in the head or body of the pancreas. Pancreatic stone clearance is achieved in 90% of the patients with CP; however, this can require multiple sessions [17]. Successful stone fragmentation was defined as stones broken into fragments of ≤2 mm, decreased stone density on radiography, increased stone surface, and heterogeneity of the stone. Ductal clearance could be complete, partial, or unsuccessful if the clearance of stones were <90%, 50–90%, or <50%, respectively. A meta-analysis reported that ESWL provided complete and partial clearance in 70% and 22% of patients, respectively, and pain was absent or mild for 2 years after ESWL in 52.7% and 33.4% of patients, respectively. After the procedure, the quality of life improved in 88.2% of patients [18]. If total stone clearance is achieved, pain relapse within the first 2 years after ESWL is rare. In the present case, half of the patients experienced stone recurrence. Small MPD stones (<5 mm) or radiolucent stones can be treated using endoscopic retrograde cholangiography (ERCP). The use of endoscopic therapy after ESWL is recommended when spontaneous clearance is not achieved. Additional endotherapy and ESWL had no benefit but were associated with longer hospital stays and higher treatment costs [19].

Large or multiple MPD stones or strictures are associated with the need for multiple ESWL sessions. In this case, pancreatic stenting before ESWL can decrease the need for additional ESWL procedures. Solitary stones, MPD stones in the pancreatic head, stones with a density on computed tomography (CT) scans of <820 HU, pancreatic stenting before the procedure, secretin administration before ESWL, and ERCP delayed by 2 days are related to better outcomes [20, 21]. Pancreatic pseudocysts are not related to MPD stone clearance [22]. The most common complication of ESWL is pancreatitis, asymptomatic hyperamylasemia, hematuria, mucosal injury, infection, skin erythema, tenderness, acute stone incarceration in the papilla, bleeding, and perforation could also be seen [23]. Contraindications for ESWL include non-correctable coagulopathy, pregnancy, and the presence of bone, calcified vessels, and lung tissue in the shockwave way [24].

Intracorporeal lithotripsy using electrohydraulic or laser lithotripsy under peroral pancreatoscopy**,** is recommended when ESWL is unavailable or stones are not fragmented after ESWL. A total of 43–100% of patients had successful MPD clearance in a systematic review. In the most extensive study of 38 patients (280 endoscopic therapy sessions, 88 of them with pancreatoscopy), complete and partial stone clearance was 24% and 10%, respectively [25, 26].
