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I would advise you to go to the ER immediately as you may be dropping hemoglobin which may be causing the tiredness. Non functioning kidney can bleed especially if it has a large cyst. Small trivial trauma is enough to start the bleeding.
Usually such conditions are anaged conservatively followed by elective removal of kidney later. Only rarely an emergency neprhectomy needed if the bleeding is not stopping.
As the ct scan was done recently there may not be another cause for this bleeding than this cyst / kidney.
Sometimes blood thinners can cause such bleeding if you are taking one.
If you have any follow up questions, please let me know.