This is the 2289th most frequent Russian word.
кишечника
The Russian word "кишечника" refers to "intestine" or "gut" in English.
In this sentence, "кишечника" is used as a possessive form of "кишечник" (gut, intestine) to indicate something related to the gut.
Здоровье кишечника влияет на общее состояние организма.
Gut health affects the overall state of the body.
Here, "кишечнике" refers to the location (inside the intestine) where the sensation was felt.
После еды он почувствовал неприятное ощущение в кишечнике.
After eating, he felt an unpleasant sensation in his intestine.
In this case, "кишечника" indicates the direct object, referring to the gut or intestine being examined.