How Hepatic Cysts Occur
Hepatic cysts arise from abnormal embryonic ductal plate development, where the ductal plate—a double cylinder of hepatoblasts surrounding portal vein branches that normally forms bile ducts—fails to properly mature and instead disconnects from the biliary tree, progressing into fluid-filled cystic structures. 1
Pathogenesis and Mechanism
The fundamental developmental defect involves ductal plate malformation during fetal development. 1 This process occurs when:
- The ductal plate, which provides the scaffold for bile duct development, undergoes abnormal maturation 1
- The malformed ductal plate disconnects from the biliary tree rather than integrating properly 1
- These disconnected structures progress into cystic lesions lined by a single cell layer 1
Cyst Characteristics and Fluid Production
The epithelial cells lining hepatic cysts retain secretory function, continuously producing fluid that generates positive luminal pressure contributing to the cyst's architecture and growth. 1 The cyst fluid composition mirrors bile but lacks bile acids or bilirubin, consisting primarily of water and electrolytes. 1
Classification Within Ciliopathies
Hepatic cysts belong to a broader category of "fibrocystic liver diseases," which are part of developmental disorders termed ciliopathies because they share cilia dysfunction in their pathogenesis. 1 This classification encompasses:
- Simple hepatic cysts (most common, prevalence 2.5-18%) 1
- Polycystic liver disease (rare, prevalence 1/10,000-1/158,000) 1
- Caroli disease and Caroli syndrome 1
- Biliary hamartomas (Von Meyenburg complexes) 1
- Mucinous cystic neoplasms (estimated prevalence <5% compared to simple cysts) 1
Acquired Forms
While congenital cysts result from ductal plate malformation, acquired hepatic cysts can develop from:
- Parasitic infection (hydatid cysts) 2, 3
- Trauma (traumatic cysts) 3
- Inflammatory processes 3
- Neoplastic processes 2
Clinical Significance
Despite the high prevalence of simple hepatic cysts in the general population (up to 18%), most remain asymptomatic and follow an indolent course. 4, 5 The developmental origin explains why these are typically benign lesions that do not require routine follow-up imaging when asymptomatic. 5