The incidence of gallstones following gastrectomy is 3.6% to 25.0% in Asia. However, it is nearly impossible to know the exact incidence of gallstones after gastrectomy because most gallstone patients are asymptomatic [5,9,10]. The incidence of gallstones tends to increase with time after gastrectomy. The incidence of gallstones was reported as a 5-year incidence of 13.6% and a 10-year of 22.1% [9]. In the general population, the prevalence of gallstones increases according to age. In 60-year-olds, the prevalence is reported as 7.3–7.9% in males and 8.2–11.9% in females in the United States and China [11,12]. Therefore, patients who underwent gastrectomy should be informed of the higher risk of gallstone formation. Abdominal imaging of ultrasonography or computed tomography is needed for gastrectomy patients with alarm symptoms such as right upper quadrant abdominal pain or dyspepsia.

The hypothesis that gastrectomy leads to a higher GB stone incidence is based on cholestasis in the GB, which can cause cholesterol formation. An increase in the cholesterol ratio contributes to cholesterol stone formation in the GB. During gastrectomy, vagal nerve branch injury or damage can occur. This result may reduce GB contractions. Another aspect is an alteration in gastrointestinal anatomy. The passage time of food material in the duodenum may be increased in patients after gastrectomy. This change decreases cholecystokinin secretion, which influences GB function [4,10]. The types of gastrectomy can also influence the incidence of gallstone formation. A larger extent of gastrectomy has a higher risk of damage to surrounding blood vessels, vagal nerves, and other tissues. In a cohort study of 698 gastrectomy patients, the incidence of gallstones was significantly higher in total gastrectomy and proximal gastrectomy than in distal gastrectomy (38.5% and 6.2% vs. 1.0%, p = 0.000) [4]. Among the subtotal gastrectomies, the Billroth II operation showed a higher incidence of gallstone formation than the Billroth Ⅰoperation. Although the mechanism was not fully understood, the change in the pattern of cholecystokinin secretion according to the type of subtotal gastrectomy might have a role in gallstone formation [9].

Based on this theory, it was believed that CBD stones developed in patients with a gastrectomy history were predominantly cholesterol stones. However, the most common type was brown pigment stones among the stones that were identified in the ERCP group in this study. Additionally, our study showed that cholecystectomy did not decrease CBD stone recurrence. The brown-pigmented CBD stones are primary CBD stones. This finding could be the main reason that cholecystectomy did not decrease the CBD stone recurrence. A recent study also concluded that a routine prophylactic cholecystectomy is not recommended after gastrectomy. During median follow-up of 48 months in 1480 patients after gastrectomy, 106 patients (7.2%) had developed gallstone formation, and only 9 patients had gallstone-related symptoms. CBD stones occurred in 20 patients (1.4%). Therefore, prophylactic cholecystectomy is not essential during gastrectomy. Other risk factors such as age, sex, body mass index, and diabetes also contribute to gallstone formation. These factors should be considered for the decision of prophylactic cholecystectomy at the time of gastrectomy [13].

The CBD stone recurrence rate was 14.5%, which is similar to that noted in patients without gastrectomy history [14]. Risk factors of recurrent CBD stones in normal gastrointestinal anatomy patients were evaluated in previous studies [15,16,17]. The risk factors were revealed as GB stones, the use of mechanical lithotripsy, dilatation of CBD, periampullary diverticulum, distal CBD angulation ≤ 135–145°, and distal CBD stricture. We applied these risk factors to patients following gastrectomy in this study. We noted that the CBD stone recurrence rate was higher in patients with periampullary diverticulum (univariate analysis, p = 0.039) and CBD stricture (multivariable analysis, HR, 3.823; 95%, CI: 1.118–13.080). Diverticulum may facilitate bacterial colonization and consequently increase the intraluminal pressure in the duodenum as well as affect the function of the sphincter of Oddi, thereby increasing the risk of CBD stone recurrence [14]. Distal CBD stricture and the consequent narrowing of the lumen may impair bile flow, hinder access and the subsequent procedure for ERCP, and cause incomplete stone removal, thereby increasing the recurrence rate [18].

Regarding the procedure types and methods, our findings indicate a higher recurrence rate when CBD stones were removed using ERCP. The altered anatomy could be attributed to the difficulty in achieving complete stone removal. A more challenging endoscopic approach is needed in patients who underwent gastrectomy compared with those without gastrectomy history. Conversely, CBD stone removal through PTBD was not affected by changes in the gastroduodenal anatomy in patients who underwent gastrectomy. However, if the intubation of an endoscope is possible at the level of the ampulla of the duodenum, the following procedures of stone removal are not much different between ERCP and PTBD. The common treatments for the removal of CBD stones are using basket (and/or retrieval balloon catheter in ERCP) or balloon sphincteroplasty (or sphincterotomy in ERCP) in ERCP and PTBD procedures. Furthermore, we observed that the balloons used in ERCP-treated patients were smaller (<12 mm diameter) than those used in PTBD-treated patients (26.8% vs. 57.8%, p = 0.002). This difference in balloon size may have contributed to impaired bile flow. In the same vein, our study observed a lower recurrence rate when a 12 mm or larger balloon (21.1% vs. 53.6%, p = 0.009) was used for dilatation, possibly indicating improved bile flow. Therefore, the difference in effectiveness between ERCP and PTBD for recurrent CBD stones in this study is mostly affected by the retrieval balloon size and not the ERCP or PTBD modality itself. However, this finding remains controversial as it has also been reported that a larger bile duct sphincter opening size may actually increase reflux and increase the risk of CBD stone recurrence [14,19]. Further prospective studies with a larger sample size are necessary.

PTBD procedure has some disadvantages, such as higher complication rates (e.g., bleeding, bile peritonitis, etc.), catheter insertion site pain, and risk of dislodgement. Hepatocutaneous tract maturation time is also needed for about 2 weeks [20]. Therefore, additional procedure is necessary in PTBD, although CBD stone was removed. In our study, the number of procedures for CBD stone removal was higher in PTBD than ERCP group (3.71 ± 1.23 vs. 1.39 ± 0.67 (mean ± SD) times, p < 0.001). In contrast, ERCP techniques have been improved with the development of various endoscopy types and accessories (e.g., pediatric colonoscope or balloon enteroscope for total gastrectomy, cap-assisted upper gastrointestinal endoscope for subtotal gastrectomy Billroth II) to overcome the hurdles of altered anatomy in patients who underwent gastrectomy [8,21]. These advancements can reduce the difference in choledocholithiasis recurrence rate between ERCP and PTBD.

This study had some limitations. First, this study had a retrospective design; provided that patients who receive treatment for CBD stones do not undergo follow-up imaging, including computed tomography, unless their symptoms recur, it is possible that the recurrence rate was underestimated, considering that asymptomatic patients with recurrence would have been missed. Second, the sample size was small, and the complete follow-up period varied widely among patients. Third, the characteristics of CBD stones were mostly unknown because the CBD stones removed through PTBD could not be accessed in this study. To determine a more accurate recurrence rate and identify risk factors [20], prospective studies with larger sample sizes and regular follow-up imaging are warranted.