Smooth Muscle Distribution Patterns of Choledochal Cysts and Their Implications for Pathogenesis and Postoperative Complications.

Objectives: Histopathologic characteristics of choledochal cysts and their clinical implications have not been previously comprehensively studied.
Methods: Smooth muscle distribution patterns and other histologic findings (inflammation, metaplasia, dysplasia, and heterotopia) in 233 surgically resected choledochal cysts were evaluated.
Results: Mean patient age was 23.3 ± 19.8 years, with male:female ratio of 0.3. Most cases were Todani type I (175 cases, 75.1%) or IVa (56 cases, 24.1%). Choledochal cysts with thin scattered/no muscle fiber (175 cases, 75.1%) were the predominant pattern and were associated with more frequent postoperative biliary stricture (P = .031), less frequent pyloric metaplasia (P = .016), and mucosal smooth muscle aggregates (P < .001) compared to cysts with thick muscle bundles. Severe chronic cholangitis (P = .049), pyloric metaplasia (P = .019), mucosal smooth muscle aggregates (P < .001), biliary intraepithelial neoplasia (P = .021), and associated bile duct (P = .021) and gallbladder carcinomas (P = .03) were more common in adults (age >20 years vs ≤20 years), suggesting that chronic irritation in association with developmental anomalies involves tumorigenesis from choledochal cysts.
Conclusion: Smooth muscle distribution pattern of choledochal cyst may predict postoperative complication, raising clinical implications of smooth muscle patterns in postoperative management of choledochal cysts.
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