Sir,my Uncle's Both The Kidneys Are Smaller Then Average.they Measure

Sir,my uncle's both the kidneys are smaller then average.they measure 7.6cm and 7.9cm.sir I wanted to ask if he can live a normal life with that???I have checked many sites saying there are chances of kidney failure.so if he can live a normal life.what are the precautions he can take and what is the diet he should follow???