When to take an emergency bathroom break,mid-tourney? (quasi-silly)

[PokrLikeItsProse]

Quasi-silly, but I recently had to consider this (although I was ultimately able to grit it out and wait).

Situation: Half-way between breaks while playing an on-line tournament, the call of nature starts feeling urgent and you feel that you must either visit the bathroom or you will almost certainly soil yourself. You are currently one table away from the final table and it is a full table.

From past experience, you know that the quickest you can be in and out is four hands, but it may take you as long as 7 hands. There is approximately a 10% chance that you will stop up the toilet and miss about 11 hands total.

When is the most advantageous position to make a run for it? Does your stack size matter? If there is a nonzero chance that you can make it to the next break, do you just try to last and go when it is no longer avoidable? Is there any tournament situation where each hand is so important that soiling your underwear is a lesser evil than missing a hand?