Purity: Doubt After Wudu Regarding the Existence of an Obstruction
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 297:
If a person doubts after performing wuḍūʾ whether or not there was something that was an obstruction to water reaching those parts of the body on which wuḍūʾ is performed, the wuḍūʾ is valid.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)