urine marking

Question
I was wondering if it is possible that when my cat was neutered at age 6 months, if they did not "get everything", like maybe both of his testicles were not descended, and now we are having trouble with him marking in our house.  He is two years old, we had he and his litter mate neutered at 6 months, and about 7 months ago he started marking in the house and we have not been able to get him to stop.  We had him checked for urinary tract infection and none is present.  He was on amitriptyline but that did not work either.  We have been using feliway diffusers and still no luck with getting it to stop.  I was wondering if maybe getting a testosterone level checked would make sense?  I am running out of ideas.  Any suggestions are welcomed.  

Answer
Karen,

Does his spray have that horrible 'tomcat' odor? If not, anything is "possible", but I doubt that is the problem. But if you can afford it, you may want to have his testosterone checked for piece of mind. Did the vet check for urinary crystals also? They are painful and the cat avoids the litterbox because he associates that pain with the litterbox. They also can cause a complete blockage which is usually fatal to a male cat when that happens.

Quite a few neutered cats, when they get to be about 2-3 years old start reacting, which can include marking, to a female scent.  Some cats have a high level of sexual mentality, even though they can't 'do' anything about it. A male can smell a female in heat up to a block away, even though they are inside cats! His behavior should stop when he can't smell any more females if that is the reason. He may also see or sense tomcats outside, and since he can't get outside to defend 'his' territory, he may be protecting it inside by marking.

There are many other emotional reasons for a cat peeing inappropriately, like changes in the house, not likeing where the litterbox is located, etc. Since I can't put every possibility in this answer, I am including some excellent links for more information:
(copy and paste or type the whole links into your address bar)

http://www.catsinternational.org/articles/housesoiling/unabridged_litterbox_1.ht...

http://cats.about.com/cs/behavioralissues/a/outsidebox_two.htm

http://www.geocities.com/heartland/pointe/9352/litterboxhelp.html

http://www.apbc.org.uk/article10.htm

AND,

here is a 'recipe' for cat urine odor removal:

1 quart of 3% hydrogen peroxide
1/4 cup baking soda
1 teaspoon of liquid soap

(3% hydrogen peroxide can be bought at most grocery and drug stores in pint and quart bottles).

Gently mix all ingredients in a non-metal container. Do not mix or shake vigorously!

The mixture is best used when fresh but can be stored. Do not keep mixture in an airtight container.  Have a VERY loose lid as baking soda and hydrogen peroxide when mixed together will release oxygen and an airtight container will explode. You can mix and keep it in large spray bottle (Home Depot, etc.) but a plastic liter or 2-liter soda bottle works just a well.

Always test for color-fastness. Hydrogen peroxide is a bleaching agent in stronger concentrations and can lighten materials that are not color-fast.

I hope this is helpful,

Tabbi