My dad had a right renal carcinoma and he had a...

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management of Renal cyst
the presence of renal on the contralateral side does not necessarily indicate malignant metastasis to the other kidney , The pet scan is indicated to reveal any sign of locoregional recurrence or distant metastasis to other organs . The detected kidney cyst should be aspirated by ultrasound sound guided means and analyzed to detect any sign of malignancy especially with the increase in size, the indication for cyst excion would by for the symptomatic cysts that compress the kidney , nephrectomy is warrented in malignant cells detected by tissue analysis of the biopsy, consult a urologist for further investigation 
Investigations 
after proper physical exam you should do cbc to detect anemia, urine analysis for hematurea and kidney function testing Urea & Cr to detect any disturbance in kidney function . Renal percutaneus US guided biopsy with tissue analysis. CT scan with IV contrast to look for cyst characteristics 
Symtomes of kidney cyst

• Flank pain
• Hematurea
• Abdominal mass 

our advice 
The detected cyst should be followed up strictly to exclude malignancy and manage properly