Ruling 55
Based on obligatory precaution, when one is emptying his bowels and/or bladder, neither the front of the body – i.e. the stomach and chest – nor the back must face qibla.1[3]
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)
1
[3] Qibla is the direction towards the Kaʿbah in Mecca.