Please tell me what indicates whether renal impairment has developed recently?

A blood test: Renal impairment is a fairly silent process. Unless severe, you won't feel a thing. It is a good idea to have a routine physical and blood work every few years and whenever you have symptoms. Yearly physical may be overrated. Kidney failure causes swelling, poor appetite and energy, altered sleep, urineferous odor among other symptoms. You can see, many diseases can cause these. See doc if unsure!