I would hydrate heavily like you are planning.
You can use glycerol and sea salt to help.
My doc(s) over the years have been critical of my lifting and will not make any considerations for it.
The few times I have gotten blood work dehydrated and after training - I according to the docs had a heart attack and or had CKD.
The very first physical I had at 19 with total blood work I went in fasting the next day after a heavy work out. Of course this was over 20 years ago so the blood work wasn't available for two days and no cell phones doctor called my parents house and asked if I was ok - like still alive - then told them to get me to the hospital as I had bloodwork that indicated I was in renal failure and had a massive heart attack.
I went the ER as advised and after many tests the doctors were pissed off for wasting their time, CPK was from muscle breakdown not cardiac, and after IV hydration kidneys normal.
Since then I have been on a roller coaster with docs and specialists over the years each time having to prove to them that having a high degree of muscle mass and and break down of tissue lead to not so normal blood values.
I now take -reluctantly 2 3 days off before blood work and go in hyper hydrated so I stay of the list of medical diagnoses that only apply to normal inactive unhealthy people.
I once did a 24 hour urine test and showed 4 grams of protein, repeated hydrated and came back trace.
I and every other body builder that juiced heavily over the years probably would show some form of Focal Segmental Glomerulosclerosis, just due to the fact of the following risk symptoms of heavy bodyweight, BP, high protein diet and the nephrotoxic effects of AAS.
As you can see from the attached article the pro bodybuilder in this study returned to "normal" after he stopped taking AAS and lost a ton of weight and changed his lifestyle and diet.
Development of Focal Segmental Glomerulosclerosis after Anabolic Steroid Abuse
I am not willing to undergo a renal biopsy unless life threatening circumstances require it, as there is a significant risk of losing a kidney from a biopsy.
I have gotten blood work done when on heavy cycles and been fine as long as I am hyperhydrated.
These days I am on sub q stuff and very low dose compared to ten years ago and feel pretty damn good, I have toned down training and eating as well as once in the 40's it's like russian roulette playing with heavy stuff and pushing protein and earth shattering weights that blow your BP through the roof.
I'd get bloodwork done JUST for peace of mind.
MG, your story sound exactly like mine, ckd, heart attack, high protein values. I even had my rotator cuff surgery scrapped until I got a stress test for my poor heart (so they thought). I do still push it, probably should calm down at 48 yo (after 30 years of gear use).