Are incidental liver cysts more commonly found in adults, especially those over 40, with the increasing use of Computed Tomography (CT) scans?

Are Incidental Liver Cysts Commonly Found with Increased CT Use?

Yes, incidental liver cysts are extremely common findings on CT scans, with benign focal liver lesions detected in up to 15% of adults undergoing imaging for other indications, and this high detection rate is directly related to the widespread use of cross-sectional imaging. 1

Prevalence and Detection Rates

The frequency of incidentally discovered liver cysts is substantial and well-documented:

• At least one benign liver lesion is found in up to 15% of patients undergoing abdominal imaging, making accurate characterization of these incidental findings a critical objective of diagnostic imaging. 1

• Simple hepatic cysts specifically occur in 15-18% of the general population in the United States, with most discovered incidentally on abdominal imaging performed for unrelated reasons. 2

• Even in patients with known primary malignancies, benign liver lesions unrelated to the malignancy are found in nearly 30% of cases, highlighting how common these incidental findings truly are. 1

Why Detection Has Increased

The rise in incidental liver cyst detection is directly attributable to imaging technology proliferation:

• An estimated 50 million CT scans are performed annually in the United States alone, which has dramatically increased the detection of asymptomatic liver lesions that would have otherwise remained undiagnosed. 1

• Ultrasound has approximately 90% sensitivity for detecting cystic liver lesions, and its widespread availability as a first-line imaging modality contributes to high detection rates. 1

• MRI is superior to both ultrasound and CT for detecting small cysts, particularly in young individuals, which further increases detection when this modality is employed. 1

Clinical Implications of High Detection Rates

Most Are Benign and Require No Action

• Simple hepatic cysts are the most common cystic liver disease and require no treatment or follow-up once diagnosed on ultrasound with typical characteristics (anechoic content, sharp smooth borders, thin walls, posterior acoustic enhancement). 1, 3

• Ultrasound should be the first imaging modality used to diagnose simple hepatic cysts, and once confirmed as simple cysts on ultrasound, CT and MRI are not indicated for further characterization. 1

Avoiding Overtreatment

A critical pitfall exists in radiologic reporting:

• There is a growing problematic trend of radiologists including "rule out biliary cystadenoma" in differential diagnoses for simple hepatic cysts, which leads to unnecessary anxiety and surgical interventions. 4

• In one study, 75% of asymptomatic patients who underwent surgery had been diagnosed with possible cystadenoma on imaging, but all were confirmed as simple benign cysts on pathology. 4

• All 19 surgical cases in this series were ultimately diagnosed as simple liver cysts on histopathology, despite preoperative imaging suggesting more concerning pathology. 4

When Further Evaluation Is Needed

Hepatic cysts demonstrating complex features require additional imaging beyond ultrasound, including: 1

• Atypical cyst wall or content
• Thick septations or nodularity
• Mural thickening
• Calcifications
• Debris-containing or hemorrhagic fluid
• Wall enhancement
• Associated bile duct dilatation

For complex cysts, MRI with heavily T2-weighted sequences should be performed to differentiate benign complicated cysts from mucinous cystic neoplasms or other pathology requiring intervention. 1

Practical Management Algorithm

1. Initial detection on any imaging modality → Characterize with ultrasound if not already performed 1

2. If simple cyst criteria met on ultrasound (anechoic, thin-walled, smooth borders, posterior enhancement) → No further imaging or follow-up needed 1

3. If complex features present → Obtain MRI with contrast to evaluate for worrisome features 1

4. Worrisome features requiring surgical evaluation include combination of thick septations/nodularity PLUS at least one additional feature (upstream biliary dilatation, internal hemorrhage, perfusional change, or <3 coexistent hepatic cysts). 1

Common Pitfalls to Avoid

• Do not order CT without contrast for cyst evaluation, as it has an ACR appropriateness rating of only 3 (usually not appropriate). 5

• Single-phase CT is inadequate for proper characterization of liver lesions; multiphasic imaging is essential if malignancy is a consideration. 5, 6

• Avoid biopsy of cystic lesions unless imaging features indicate possible malignancy, as this increases bleeding risk (9-12%) without adding diagnostic value for simple cysts. 5

• Resist pressure to operate on asymptomatic simple cysts even when radiology reports include "rule out cystadenoma" in the differential, as this frequently leads to unnecessary surgery. 4