Biliary Hamartomas

Biliary hamartomas (von Meyenburg complexes) are benign liver lesions made of small, dilated bile ducts in fibrous stroma, from persistence of embryonic ductal plate remnants. They are usually multiple, small and asymptomatic.

They are found in 0.6% to 5.6% of autopsies and a smaller share of imaging studies. They are often incidental on imaging in adults, and may coexist with polycystic liver and kidney disease and congenital hepatic fibrosis.

Lesions are typically under 15 mm. Complications are rare: cholangitis, portal hypertension in diffuse disease and, very rarely, cholangiocarcinoma.

Pathophysiology.

Failure of involution of the ductal plate leads to cystically dilated ducts within a fibrous stroma, with a connection to the biliary tree.

Usually none. Liver tests are normal or mildly cholestatic. Abdominal pain, fever or jaundice are uncommon, and suggest cholangitis or a different diagnosis.

Ultrasound shows multiple small hyperechoic or hypoechoic lesions, with comet tail artefacts. Magnetic resonance imaging shows multiple small, round or irregular T2 hyperintense cysts under 15 mm without communication with the bile ducts on cholangiography, giving a "starry sky" appearance, and with thin rim enhancement in some. Biopsy is reserved for doubt because imaging can mimic metastases. Review kidney imaging for polycystic disease.

Differential diagnosis.

• Liver metastases.
• Simple hepatic cysts.
• Caroli disease.
• Polycystic liver disease.
• Microabscesses.
• Hepatic lymphoma.

Reassure the patient. No treatment is needed for typical asymptomatic lesions. Follow up imaging at 6 to 12 months confirms stability if the diagnosis is uncertain, and long term follow up is not required for typical findings. Biopsy or resection is done for a growing or atypical lesion, or a solid enhancing nodule, to exclude cholangiocarcinoma. Treat cholangitis with antibiotics:

• Ciprofloxacin: 500 mg orally every 12 hours for 7 to 10 days; maximum 1,500 mg daily; monitor QTc, tendon pain and Clostridioides difficile; reduce to 250 to 500 mg every 12 hours when creatinine clearance is 30 to 50 mL/min and to 250 to 500 mg once daily under 30 mL/min.

Monitoring. Imaging at 6 to 12 months if uncertain; symptoms thereafter.

Referral and escalation. Hepatology or hepatobiliary surgery for atypical lesions, complications or associated polycystic or fibrocystic disease.