urine is a very "clean" liquid..as its been filtered many many times as it goes through the system. The reason people end up with urinary tract infections is when dirt or bacteria is allowed to enter, thus infecting the bladder, or "holding tank" so to speak.

Feces, however is a waste byproduct and NOT filtered...

Grant me the senility to forget the people I never liked,the good fortune to run into the ones I do,and the eyesight to tell the difference.