Follow up: 1st reading of renal ct said probable malignancy due to contrast uptake. 2nd radiologist - says benign. who do i believe?

Repeat CT: To be absolutely sure that a renal mass is benign, you need to have a study with and without contrast. The non-contrast study will be compared to the contrast study. If there is no enhancement of the mass, than this is almost always a benign process. If there is enhancement, than it is a solid lesion. See if you can get a referral to a third radiologist who is an expert in renal imaging.

Renal : A dedicated ct or MRI should be done. If lesion demonstrates enhancement and then washout on delayed imaging it is suspicious. There are different classifications for renal mass/cyst called bosniak classification. If you want someone to review lmk.

Urology referral: Given the difference in opinion of the two radiologists, i would strongly suggest you seek a consultation with a urologist who specializes in kidney pathology. Ultimately, it is the urologist usually helps you to make decisions about whether a kidney mass can be safely watched, whether it should be biopsied or whether it should be removed or ablated. The urologist also provides long term followup.