renal calculus vs kidney stone

renal calculus and kidney stone both are nouns.

Word	Noun	Adjective	Verb	Adverb
renal calculus	Yes	No	No	No
kidney stone	Yes	No	No	No

As nouns, renal calculus and kidney stone are synonyms defined as:

Other synonyms of renal calculus include nephrolith, urinary calculus.

renal calculus (noun)	kidney stone (noun)
a calculus formed in the kidney	a calculus formed in the kidney