<s>[INST] My father has recently been operated to remove right kidney because of suspected renal carcinoma and the tumor size was very big. Now he is detected with cortical cyst measuring 14 x 13 mm on the left kidney. Is there any thing to press the panic button? [/INST] Good Day, and thank you for being with Chat Doctor ! Simple Renal cortical cysts are benign conditions and doesn't warrant any treatment or intervention. The cyst of your father is very small and would not transform into a cancer 99% of the time. I would suggest having him Chat Doctor. 5-2 liters of water and avoid pain medications. If he has hypertension or diabetes then he should ensure they are well controlled to take care of his remaining kidney. BFUP with ultrasound to monitor the cyst is advised together with biannual urinalysis and serum creatinine determination.  I hope I have succeeded in providing the information you were looking for. Please feel free to write back to me for any further clarifications at: http://www.ChatDoctor .com/doctors/ </s>