Thanks for all these additional details.
Well, as you had a recent kidney surgery, so this could have resulted in such condition.
Having frequent urination, could be related with- Urinary tract infection, Yes, it could also cause passage of blood and may be visible as dry blood in underwear.
As such to diagnose the cause you require urine test, blood sugar test , detailed clinical checkup by doctor .
So please get it checked from doctor.
Your doctor can advise for a Urine test, It can detect bacteria in your urine. It is fairly reliable and usually no further test is needed.
It can be managed with antibiotics like- Nitrofurantoin, Trimethoprim-sulfamethoxazole, Amoxicillin, Cephalosporins.
For the time, Drink plenty of fluids, Take Cranberry juice.
You should Avoid tight underwear.
Please get it evaluated from your doctor. It can be managed with antibiotics.
This is not a serious issue and can be managed by your doctor.
Hope this helped
If you have any further question then you can ask me.
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