Zappa wrote a song, on the "Joe's Garage" album titled "Why Does It Hurt When I Pee?"
http://www.lyricsdepot.com/frank-zappa/why-does-it-hurt-when-i-pee.html
Reminds me of the country song that never got published, 'cause the songwriter refused to get it renamed...he wanted to stick with "I Love You So F*cking Much I Can't P*ss At Night"