All cat owners need to read this article: Help… my cat can’t pee! Feline Urethral Obstruction: Be Aware.

My sweet, beautiful, gorgeous boy died of this today. I didn’t even know it was possible for this to happen! The first signs are very similar to constipation and that’s what I thought it was when he spent an abnormal amount of time in the litter box. I have, or had, now, two cats. When I scoop out a pee, how am I to know which one did it? And by the time I noticed, it was too late.
Everyone everywhere is always telling you to spay and neuter your pets. They don’t tell you about this and they should. It should be included in the information they give you about the surgery. Before you comment, no, I am NOT advocating against spaying/neutering, but for the pet owner’s being completely informed.
Please, if you know anyone who has a cat, especially a neutered male, please tell them about this.