After surgery like this, a release to return to weight lifting is best answered by your surgeon. Weight lifting will not affect your single kidney and would have no adverse effects on your kidney function, but because of the surgical changes and healing after the surgery, it is best to get clearance from your surgeon for weight lifting.
I do not think you would need to take a multiple vitamin. I do recommend a low salt diet and am an advocate for the DASH diet. You can review the DASH diet at: https://www.nhlbi.nih.gov/health/health-topics/topics/dash
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