BismiLahi Rahmani Rahim:
Does touching ones anus or penus invalidate the wudu?
There is two answers regarding it but the most correct is that it does not invalidate it.
As for the anus there is no proof on it.
And what has been said in the hadith whomever touches his sexual organ (without a barrier) must perform wudu" it is not general applying to all cases as it is explained by other narrations.
As for the penus the hadith about it whomever touches his penus (without a barrier) must perform wudu is gathered with the hadith verily it is a part of your body.
For more details see my letter in my website on the link below.
Written by Shaykh Maher al-Qahtani
Translated by Abu Maryam Jaouad al maghrebi
http://www.al-sunan.org/vb/forumdisplay.php?f=19