Objective To investigate the clinical characteristics of choledocholithiasis com-bined with periampullary diverticulum and influencing factor for difficult cannulation of endoscopic retrograde cholangiopancreatography (ERCP).

Methods The retrospective case-control study was conducted. The clinical data of 1 920 patients who underwent ERCP for choledocholithiasis in 15 medical centers, including the First Hospital of Lanzhou University, et al, from July 2015 to December 2017 were collected. There were 915 males and 1 005 females, aged (63±16)years. Of 1 920 patients, there were 228 cases with periampullary diverticulum and 1 692 cases without periampullary diverticulum. Observation indicators: (1) clinical characteristics of patients with choledocholithiasis; (2) intraoperative and postoperative situations of patients undergoing ERCP for choledocholithiasis; (3) influencing factor analysis for difficult cannulation in patients undergoing ERCP for choledocholithiasis. Measurement data with normal distribution were represented as Mean±SD, and comparison between groups was conducted using the independent sample t test. Measurement data with skewed distribution were represented as M(range) or M(Q₁,Q₃), and com-parison between groups was conducted using the Wilcoxon rank sum test. Count data were described as absolute numbers or percentages, and comparison between groups was conducted using the chi-square test or Fisher exact probability. The Logistic regression model was used for univariate and multivariate analyses.

Results (1) Clinical characteristics of patients with choledocholithiasis. Age, body mass index, cases with complications as chronic obstructive pulmonary disease, diameter of common bile duct, cases with diameter of common bile duct as <8 mm, 8‒12 mm, >12 mm, diameter of stone, cases with number of stones as single and multiple were (69±12)years, (23.3±3.0)kg/m², 16, (14±4)mm, 11, 95, 122, (12±4)mm, 89, 139 in patients with choledocholithiasis combined with periampullary diverticulum, versus (62±16)years, (23.8±2.8)kg/m², 67, (12±4)mm, 159, 892, 641, (10±4)mm, 817, 875 in patients with choledocholithiasis not combined with periampullary diver-ticulum, showing significant differences in the above indicators between the two groups (t=‒7.55, 2.45, χ²=4.54, t=‒4.92, Z=4.66, t=‒7.31, χ²=6.90, P<0.05). (2) Intraoperative and postoperative situations of patients undergoing ERCP for choledocholithiasis. The balloon expansion diameter, cases with intraoperative bleeding, cases with hemorrhage management of submucosal injection, hemostatic clip, spray hemostasis, electrocoagulation hemostasis and other treatment, cases with endoscopic plastic stent placement, cases with endoscopic nasal bile duct drainage, cases with mechanical lithotripsy, cases with stone complete clearing, cases with difficult cannulation, cases with delayed intubation, cases undergoing >5 times of cannulation attempts, cannulation time, X-ray exposure time, operation time were 10.0(range, 8.5‒12.0)mm, 56, 6, 5, 43, 1, 1, 52, 177, 67, 201, 74, 38, 74, (7.4±3.1)minutes, (6±3)minutes, (46±19)minutes in patients with choledocholithiasis combined with periampullary diverticulum, versus 9.0(range, 8.0‒11.0)mm, 243, 35, 14, 109, 73, 12, 230, 1 457, 167, 1 565, 395, 171, 395, (6.6±2.9)minutes, (6±5)minutes, (41±17)minutes in patients with choledocholithiasis not combined with periampullary diverticulum, showing significant differences in the above indicators between the two groups (Z=6.31, χ²=15.90, 26.02, 13.61, 11.40, 71.51, 5.12, 9.04, 8.92, 9.04, t=‒3.89, 2.67, ‒3.61, P<0.05). (3) Influencing factor analysis for difficult cannulation in patients undergoing ERCP for choledocholithiasis. Results of multivariate analysis showed total bilirubin >30 umol/L, number of stones >1, combined with periampullary diverticulum were indepen-dent risk factors for difficult cannulation in patients with periampullary diverticulum who underwent ERCP for choledocholithiasis (odds ratio=1.31, 1.48, 1.44, 95% confidence interval as 1.06‒1.61, 1.20‒1.84, 1.06‒1.95, P<0.05). Results of further analysis showed that, of 1 920 patients undergoing ERCP for choledocholithiasis, the incidence of postoperative pancreatitis was 17.271%(81/469) and 8.132%(118/1 451) in the 469 cases with difficult cannulation and 1 451 cases without difficult cannula-tion, respectively, showing a significant difference between them (χ²=31.86, P<0.05). In the 1 692 patients with choledocholithiasis not combined with periampullary diverticulum, the incidence of postopera-tive pancreatitis was 17.722%(70/395) and 8.250%(107/1 297) in 395 cases with difficult cannula-tion and 1 297 cases without difficult cannulation, respectively, showing a significant difference between them (χ²=29.00, P<0.05). In the 228 patients with choledocholithiasis combined with peri-ampullary diverticulum, the incidence of postoperative pancreatitis was 14.865%(11/74) and 7.143%(11/154) in 74 cases with difficult cannulation and 154 cases without difficult cannulation, respectively, showing no significant difference between them (χ²=3.42, P>0.05).

Conclusions Compared with patients with choledocholithiasis not combined with periampullary divertioulum, periampullary divertioulum often occurs in choledocholithiasis patients of elderly and low body mass index. The proportion of chronic obstructive pulmonary disease is high in choledocholithiasis patients with periampullary diverticulum, and the diameter of stone is large, the number of stone is more in these patients. Combined with periampullary diverticulum will increase the difficult of cannulation and the ratio of patient with mechanical lithotripsy, and reduce the ratio of patient with stone complete clearing without increasing postoperative complications of choledocholithiasis patients undergoing ERCP. Total bilirubin >30 μmol/L, number of stones >1, combined with periampullary diverticulum are independent risk factors for difficult cannulation in patients of periampullary diverticulum who underwent ERCP for choledocholithiasis.