fistulous withers vs fistula

fistulous withers and fistula both are nouns.

Word	Noun	Adjective	Verb	Adverb
fistulous withers	Yes	No	No	No
fistula	Yes	No	No	No

As nouns, fistulous withers and fistula are synonyms defined as:

fistulous withers and fistula: a chronic inflammation of the withers of a horse

fistulous withers (noun)	fistula (noun)
a chronic inflammation of the withers of a horse	an abnormal passage leading from a suppurating cavity to the body surface
	a chronic inflammation of the withers of a horse