I have a five-step ritual.
1. Mute myself. 2. Double check I am muted. 3. Ask, "Can anyone hear me?" 4. Ask, "Can anyone hear me?" again, louder. 5. State, "I'm about to urinate."
Increasingly embarrassing failsafes, but not as embarrassing as broadcasting a bathroom break. I'm happy that I never needed anything past layer 2.