Purity: Impurity on Body Parts Not Included in Wudu
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 276:
If a part of the body on which wuḍūʾ is not performed is impure, the wuḍūʾ is valid. However, if one has not purified the urinary outlet or the anus, the recommended precaution is that one should first purify it and then perform wuḍūʾ.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)