intestinal flu vs stomach flu

intestinal flu and stomach flu both are nouns.

Word	Noun	Adjective	Verb	Adverb
intestinal flu	Yes	No	No	No
stomach flu	Yes	No	No	No

As nouns, intestinal flu and stomach flu are synonyms defined as:

intestinal flu and stomach flu: inflammation of the stomach and intestines; can be caused by Salmonella enteritidis

Other synonyms of intestinal flu include gastroenteritis.

intestinal flu (noun)	stomach flu (noun)
inflammation of the stomach and intestines; can be caused by Salmonella enteritidis	inflammation of the stomach and intestines; can be caused by Salmonella enteritidis