What are the causes of liver cysts?

Causes of Liver Cysts

Liver cysts arise primarily from abnormal fetal ductal plate maturation, where the ductal plate disconnects from the biliary tree and progresses into cystic structures. 1 This developmental abnormality is the fundamental cause of most non-infectious cystic liver lesions.

Main Categories of Liver Cysts

1. Developmental/Congenital Causes

• Simple hepatic cysts

  • Most common type (prevalence 2.5-18.0% of population) 1
  • Arise from aberrant bile duct cells during embryonic development 2
  • Characterized by fluid-filled cavities lined by a single cell layer 1

• Polycystic Liver Disease (PLD)

  • Rare genetic disorder (prevalence 1/10,000-1/158,000) 1
  • Defined by presence of >10 hepatic cysts 1
  • Often associated with polycystic kidney disease
  • Part of the broader category of "ciliopathies" due to shared cilia dysfunction 1

• Biliary Hamartomas (Von Meyenburg complexes)

  • Result from ductal plate malformations 1
  • Appear as tiny (<1 cm) hypodense lesions scattered throughout the liver 1
  • Can mimic liver metastases on imaging

• Caroli Disease and Caroli Syndrome

  • Characterized by dilatation of intrahepatic bile ducts 1
  • Caroli disease: limited to dilatation of larger intrahepatic bile ducts
  • Caroli syndrome: combines bile duct dilatation with congenital hepatic fibrosis 1

• Peribiliary Cysts

  • Develop along the portal tracts 1

2. Neoplastic Causes

• Mucinous Cystic Neoplasms (MCNs)
  • Rare (<5% compared to simple hepatic cysts) 1
  • Also referred to as biliary cystadenoma or biliary cystadenocarcinoma
  • Significant clinical concern due to malignant transformation rates up to 30% 1

3. Infectious Causes

• Pyogenic Liver Abscess

  • Caused by bacterial infection 3
  • Requires antibiotics targeting gram-negative and anaerobic bacteria 3

• Amoebic Liver Abscess

  • Caused by Entamoeba histolytica 3
  • Responds well to metronidazole or tinidazole treatment 3

• Hydatid Cysts (Echinococcosis)

  • Caused by Echinococcus granulosus (most common) or E. multilocularis 1
  • Incubation period: months to years 1
  • Transmission: ingestion of eggs from canine feces 1
  • Liver is affected in 70% of cases 1

• Post-infectious Cysts

  • Can develop as sequelae of treated amoebic or pyogenic abscesses 4

4. Traumatic/Iatrogenic Causes

• Post-traumatic Cysts
  • Can develop following liver trauma or contusion 3
  • May be complicated by bleeding or infection

5. Miscellaneous Causes

• Hemorrhagic Cysts

  • Result from bleeding into pre-existing cysts 5

• Inflammatory Cysts

  • Include pseudocysts and encapsulated/loculated pericardial effusions 1
  • Can be caused by rheumatic pericarditis, bacterial infection, trauma, or cardiac surgery 1

Clinical Significance and Complications

Complications of Liver Cysts

• Cyst hemorrhage

  • Common complication but incidence rates unknown 1
  • May lead to cyst rupture

• Cyst infection

  • Usually caused by gut bacteria, with E. coli being the most frequent isolate 1
  • Requires prompt antibiotic therapy to prevent sepsis and death

• Cyst rupture

  • Rare complication, typically occurring in large cysts (median size >10 cm) 1
  • Risk factors include cyst hemorrhage, infection, trauma, and interventions
  • Can lead to peritoneal space contamination and anaphylaxis (especially with hydatid cysts) 1

• Biliary compression

  • Can cause bile duct dilatation, elevated alkaline phosphatase, and jaundice 1
  • Usually associated with centrally located cysts (liver segment 4)

Diagnostic Approach

Ultrasound is the first-line imaging modality for diagnosing liver cysts 1, 2. Simple cysts appear as round or oval-shaped, anechoic lesions with sharp borders and thin walls. For complex cysts or suspected malignancy, contrast-enhanced ultrasound, CT, or MRI may be required for further characterization 5.

For suspected infectious cysts, particularly hydatid disease, serology and specific imaging patterns are essential for diagnosis 1.

Management Considerations

Treatment depends on the type of cyst, symptoms, and complications:

1. Asymptomatic simple cysts: No treatment required 2

2. Symptomatic simple cysts: Options include percutaneous aspiration with sclerotherapy or surgical de-roofing 2

3. Infectious cysts:

   • Pyogenic abscess: Antibiotics with or without drainage 3
   • Amoebic abscess: Metronidazole or tinidazole 3
   • Hydatid cysts: Albendazole with or without surgical intervention 1

4. Polycystic liver disease: Careful patient selection for intervention due to high morbidity and mortality rates 6

5. Neoplastic cysts: Surgical resection for mucinous cystic neoplasms due to malignant potential 1

Understanding the specific cause of liver cysts is crucial for appropriate management and to avoid unnecessary interventions in benign, asymptomatic cases.