Simple hepatic cyst

Simple hepatic cysts are common benign liver lesions and have no malignant potential.

Epidemiology

There one of the commonest of liver lesions and occur in ~ 2 - 7% of the population ^1-2. There may be a slight female predilection.

Clinical presentation

Hepatic cysts are typically discovered incidentally and almost always asymptomatic.

Pathology

These lesions may be isolated or multiple and vary from a few millimeters to several centimeters in diameter. Simple hepatic cysts are benign developmental lesions that do not communicate with the biliary tree ². The current theory regarding the origin of true hepatic cysts is that they originate from hamartomatous tissue. On histopathological analysis, true hepatic cysts contain serous fluid and are lined by a nearly imperceptible wall consisting of cuboidal epithelium, identical to that of bile ducts, and a thin underlying rim of fibrous stroma ².

Location

While they can occur anywhere in the liver, there may be greater predilection towards the right lobe of the liver ³ (Wonder why ? more liver tissue ?).

Associations

Certain diseases are associated with multiple hepatic cysts and include

• polycystic liver disease
• polycystic kidney disease -  autosomal dominant polycystic kidney disease (ADPKD) : hepatic cysts may be seen in ~ 40% of those with ADPKD ².
• von Hippel lindau disease

Radiographic features

General imaging features

They are typically round or ovoid in shape and have well-defined margins

CT

On CT, a hepatic cyst demonstrates homogenous hypoettenuation (water attenuation) with around 0 - 10 HU. The wall is usually imperceptible, and the cyst does not enhance after intravenous administration of contrast material

MRI

On MR imaging a hepatic cyst have signal characteristics iso-intense relative to water and does not enhance after administration of contrast. The cyst wall is very thin or even imperceptible ⁴.

Therefore signal characteristics are

• T1 : homogeneous very low signal intensity
• T2 : increase in signal intensity

In instances of intracystic haemorrhage which is a rare complication in simple hepatic cysts, the signal intensity is high, with a fluid-fluid level, on both T1- and T2-weighted images when mixed blood products are present ².

Differential diagnosis

General imaging differential considerations include other cystic liver lesions, including :

• hepatic hydatid cyst(s)
• hepatic abscess(es)
• biliary cystadenoma(s)
• choledochal cyst - communicates with biliary tree

On CT and T2 MRI images also consider

• biliary hamartomas