An extreme case of diarrhea, akin to that experienced by the Japanese housed at the American Manzanar concentration camp. Usually used in a situation in which one will have to do their business in a public bathroom, again relating to the situation at Manzanar.
That meat they served at the cafeteria today gave me a serious case of the Manzanar runs; I'll have to blow up the toilet during English class it seems.