Complex renal cysts are often incidentally detected on imaging. The differential diagnosis of the complex renal cyst includes various benign cystic lesions, which are based on the Bosniak classification scheme. Currently the standard of care in evaluating a complex renal cyst is using a contrast-enhanced computed tomography (CT) scan, or a contrast-enhanced magnetic resonance imaging (MRI) scan. Since both of these modalities present adverse events due to frequent high doses of radiation, a technique such as a contrast-enhanced ultrasound (CEUS) can be used to obtain the same results, without having to impose high doses of radiation upon a patient.

By evaluating complex renal cysts using a contrast-enhanced ultrasound (CEUS), it can be established as to whether or not the results are better, the same, or worse, when compared to CT and/or MRI scans.

Inclusion Criteria:

• at least 18 years old and capable of giving informed consent
• all patients undergoing CT evaluation of complex renal cysts at our centre (either initially or in follow-up)
• A complex renal cyst defined as Bosniak IIF, III or IV

Exclusion Criteria:

• pregnant patients
• patients with contrast allergies
• patients with non-cystic, solid renal masses
• patients with simple cysts (Bosniak class I and II)