Open-label Pilot Evaluating Renal Lesions w/ Contrast-enhaced US in Patients w/ Renal Cancer

Inclusion Criteria: 1. Able to provide written informed consent 2. Willing to comply with protocol requirements 3. At least 18 years of age 4. Cohort 1: * Be eligible for radical or partial nephrectomy or ablative therapy based upon at least one renal lesion identified during previous contrast enhanced CT or MR. OR 5. Cohort 2: * High risk group (patient recommended for routine surveillance screening for renal malignancy) * Have at least one kidney lesion identified but incompletely characterized on a screening US, CT, or MR exam Exclusion Criteria: 1. Critically ill or medically unstable and whose critical course during the observation period would be unpredictable (e.g., chronic obstructive pulmonary disease (COPD) requiring oxygen) 2. Known hypersensitivity to sulfur hexafluoride or to any component of perflutren lipid (Definity®) 3. Right to left shunt, severe pulmonary hypertension (Pulmonary artery pressure \>90mmHg), or adult respiratory distress syndrome 4. Active cardiac disease including any of the following: * Severe congestive heart failure (class IV in accordance with the classification of the New York Heart Association) * Unstable angina. * Severe arrhythmia (i.e. ventricular tachycardia, flutter fibrillation; ventricular premature complexes occurring close to the preceding T-wave, multifocal complexes). * Myocardial infarction within 14 days prior to the date of proposed Definity® administration. * Uncontrolled systemic hypertension (Blood pressure: systolic blood pressure (BP) \>150 mm Hg and/or diastolic BP \>90 mm Hg despite optimal medical management not controllable by medication to achieve BP \<15/90) 5. Is in an intensive care setting 6. Has an unstable neurological disease (e.g recent stroke or TIA symptoms (\<3 months)) cerebrovascular accident (including transient ischemic attacks (TIAs) within the 3 months before signing of informed consent 7. Undergone an invasive procedure on kidney lesion (e.g. tissue biopsy, surgery, nonsurgical cytoreductive procedure) in-between identification of lesion via US without contrast and perflutren lipid administration 8. Has previously been entered into this study or has received an investigational drug within the 30 days prior to admission into this study 9. Has any other medical condition or other circumstances that would significantly decrease the chances of obtaining reliable data or of achieving the study objectives such as: * Mental illness * Drug abuse 10. Female patient who is pregnant or lactating (the possibility of pregnancy has to be excluded by negative serum or urine B-HCG results, obtained within 24 hours before the perflutren lipid administration, or on the basis of patient history, e.g.: tubal ligation, hysterectomy or a minimum of 1 year without menses).