All drugs, not just
Benazepril, cause issues for the kidneys. Why? Because most drugs are metabolized in the digestive system
and waste by-products need to be cleared out of the system by the kidneys. Most of the by-products are toxic, so they have to be removed from the body - and the already damaged kidneys can find this work hard to perform, so some toxins end up circulating back in the bloodstream.
Benazepril, thankfully, is metabolized chiefly by the liver.