Classification of anatomical morphology of cystic duct and its association with gallstone

Abstract

Background: Gallstones are common lesions that often require surgical intervention. Laparoscopic cholecystectomy is the treatment of choice for symptomatic gallstones. Preoperatively, the anatomical morphology of the cystic duct (CD), needs to be accurately recognized, especially when anatomical variations occur in the CD, which is otherwise prone to bile duct injury. However, at present, there is no optimal classification system for CD morphology applicable in clinical practice, and the relationship between anatomical variations in CDs and gallstones remains to be explored.

Aim: To create a more comprehensive clinically applicable classification of the morphology of CD and to explore the correlations between anatomic variants of CD and gallstones.

Methods: A total of 300 patients were retrospectively enrolled from October 2021 to January 2022. The patients were divided into two groups: The gallstone group and the nongallstone group. Relevant clinical data and anatomical data of the CD based on magnetic resonance cholangiopancreatography (MRCP) were collected and analyzed to propose a morphological classification system of the CD and to explore its relationship with gallstones. Multivariate analysis was performed using logistic regression analyses to identify the independent risk factors using variables that were significant in the univariate analysis.

Results: Of the 300 patients enrolled in this study, 200 (66.7%) had gallstones. The mean age was 48.10 ± 13.30 years, 142 (47.3%) were male, and 158 (52.7%) were female. A total of 55.7% of the patients had a body mass index (BMI) ≥ 24 kg/m². Based on the MRCP, the CD anatomical typology is divided into four types: Type I: Linear, type II: n-shaped, type III: S-shaped, and type IV: W-shaped. Univariate analysis revealed differences between the gallstone and nongallstone groups in relation to sex, BMI, cholesterol, triglycerides, morphology of CD, site of CD insertion into the extrahepatic bile duct, length of CD, and angle between the common hepatic duct and CD. According to the multivariate analysis, female, BMI (≥ 24 kg/m²), and CD morphology [n-shaped: Odds ratio (OR) = 10.97, 95% confidence interval (95%CI): 5.22-23.07, P < 0.001; S-shaped: OR = 4.43, 95%CI: 1.64-11.95, P = 0.003; W-shaped: OR = 7.74, 95%CI: 1.88-31.78, P = 0.005] were significantly associated with gallstones.

Conclusion: The present study details the morphological variation in the CD and confirms that CD tortuosity is an independent risk factor for gallstones.

Keywords: Anatomy; Classification; Cystic duct; Gallstone; Magnetic resonance cholangiopancreatography; Risk factor.

Figure 1

The length of cystic duct and < common hepatic duct were measured on magnetic resonance cholangiopancreatography images. A: Measure relevant anatomy: Cystic duct (CD) (white arrow), common hepatic duct (CHD) (black arrow), common bile duct (green arrow); B: Length of CD: Measurements are taken from the beginning of the cystic duct and along the trajectory of the CD until it reaches the point of confluence of the CD (white arrow) into the CHD (black arrow); C: < CHD: The angle between the common hepatic duct (black arrow) and the cystic duct (white arrow).

Figure 2

The classification of intrahepatic bile duct anatomy. A: Type A: The right posterior duct (RPD) (black arrow) converges into the right hepatic duct (yellow arrow); B: Type B: The RPD (black arrow) converges into the junction of the right and left hepatic ducts, and the three show a three-fork type; C: Type C: The RPD (black arrow) converges into the left hepatic duct (blue arrow); D: Type D: The RPD (black arrow) converges into the extrahepatic bile duct.

Figure 3

The classification of the morphology of cystic duct and model diagram. A: Type I: Linear, cystic duct (CD) (white arrow) straight into extrahepatic bile duct (EHBD) with no tortuosity; B: Type II: n-shaped, CD (white arrow) has a bend in the shape of an n; C: Type III: S-shaped, CD (white arrow) converges in an S-shape into the EHBD; D: Type IV: W-shaped, CD (white arrow) converges into the EHBD in a W-shape; E: Type I: Linear; F: Type II: n-shaped; G: Type III: S-shaped; H: Type IV: W-shaped.

Figure 4

The cystic duct converges into the intrahepatic bile duct. A: The cystic duct (CD) (white arrow) converges into the right hepatic duct (green arrow); B: The CD converges into the left hepatic duct (blue arrow); C: The CD converges into the confluence of the right and left hepatic ducts.