Well I am showing you something here that's not really visible in context (and it is still a draft). It happens in a scene that makes it clear we're in a pretty grimy and grubby part of the city. My principal objection isn't to the swear word itself. I just don't feel it's necessary in this context. When you talk about 'stench of cats' I think it brings up the picture.
Though maybe I'm wrong and it's too subtle.

Interestingly I got a whine from someone on Twitter who wrote...

...re-write paints a completely different picture (for a cat person at least). Swearwords are important.

But maybe I should put up a poll: Vote on whether the word 'piss' will be included in my 2012 book! Well actually it will be elsewhere. Just not sure about here.