According to his gastroenterologist, it's actually a colon problem. Most people have relatively short colons that empty via the anus. Like many Republicans, Trump's YUGE mega-colon empties directly into his skull. His shit is brownish orange in color and that explains his strange orange complexion and why that rat-like creature sitting on his head orange as well.
Trump being orange will assure him the Umpa Lumpa vote. I think he hires Umpa Lumpas but doesn't pay them but they are happy to swallow his shit.