A liver cyst is a fluid-filled sac that develops within the liver tissue. These growths are common, with a prevalence reported as high as 15% to 18% in some studies. Most liver cysts are benign (non-cancerous) and often cause no symptoms or health issues. They are thought to be developmental in origin. The appearance of these cysts on medical scans is the primary method for determining their nature and deciding on follow-up.
How Liver Cysts Are Discovered
Liver cysts are frequently discovered by chance when a person undergoes imaging for an unrelated health concern. Since the majority of these cysts do not produce noticeable signs, they are often referred to as incidental findings. Common imaging methods that reveal these cysts include ultrasound, computed tomography (CT) scans, and magnetic resonance imaging (MRI).
When a cyst does cause symptoms, it is usually because it has grown large enough to press on nearby organs or structures. These symptoms are typically non-specific, such as abdominal fullness, bloating, or pain in the upper right part of the abdomen. A doctor may then specifically order one of these imaging tests to investigate the cause of the patient’s discomfort.
The Typical Appearance of a Simple Cyst
A simple liver cyst has a distinctive appearance on imaging, which allows medical professionals to classify it as benign without needing further intervention. On an ultrasound, a simple cyst appears as a perfectly round or oval structure with smooth, sharply defined borders. The internal contents are uniformly dark, described as “anechoic,” indicating the structure is filled with clear fluid and contains no solid material.
The wall surrounding the cyst is characteristically very thin or even imperceptible, and there should be no internal divisions, known as septations. “Posterior acoustic enhancement” is a classic ultrasound sign, where sound waves pass straight through the fluid, making the tissue behind the cyst appear brighter. On a CT scan, a simple cyst shows a uniformly low density, similar to water, and it does not absorb or “enhance” after intravenous contrast dye is administered. This consistent appearance confirms the diagnosis of a simple, benign cyst.
Understanding Complex and Atypical Liver Cysts
Not all cysts exhibit the uniform appearance of a simple cyst; those that deviate are categorized as complex or atypical. Complex cysts display features suggesting the fluid is not just clear water, or that the wall structure has been altered, which warrants closer examination. Key features include having irregular or thick walls.
The presence of internal debris, thick septations, or solid components inside the cyst indicates a complex nature. This atypical appearance can be caused by conditions such as a hemorrhagic cyst (where bleeding has occurred), an infected cyst, or a parasitic infection. Imaging features like mural nodules (small growths on the inner wall) or calcifications also signal complexity. These visual differences prompt medical providers to use advanced imaging like MRI to better characterize the contents and rule out concerning diagnoses, such as cystic tumors.
Management and Monitoring
The management strategy for a liver cyst depends heavily on its appearance on imaging and whether it is causing symptoms. For simple, asymptomatic cysts, the recommended approach is typically no treatment. Physicians may suggest a follow-up ultrasound within six to twelve months to confirm the cyst remains stable. If it is unchanged, further monitoring may not be necessary.
If a cyst is large, causing uncomfortable symptoms, or has complex features that raise suspicion, intervention may be considered. Treatment options range from percutaneous aspiration (where a needle is guided by imaging to drain the fluid) to surgical procedures. Surgical options often involve “deroofing,” which means removing a portion of the cyst wall to prevent fluid from reaccumulating. Consulting with a specialist is recommended when a complex cyst is identified or a simple cyst becomes problematic.