renal failure vs kidney disease

renal failure and kidney disease both are nouns.

Word	Noun	Adjective	Verb	Adverb
renal failure	Yes	No	No	No
kidney disease	Yes	No	No	No

As nouns, kidney disease is a hypernym of renal failure; that is, kidney disease is a word with a broader meaning than renal failure:

renal failure: inability of the kidneys to excrete wastes and to help maintain the electrolyte balance
kidney disease: a disease affecting the kidneys

Other hypernyms of renal failure include failure, nephropathy, nephrosis, renal disorder.

renal failure (noun)	kidney disease (noun)
inability of the kidneys to excrete wastes and to help maintain the electrolyte balance	a disease affecting the kidneys