male cat-diarrhea

Question
I rescued a male cat unneutered that is about 2 yrs. old.  He had a Upper Resp. Infection and I treated him with Clavomox for 14 days.  Here are his current symptoms:

Shakes his head and scratches until it bleeds - he just made it bleed today; normally he just shakes his head.

I have never know him to not have diarrhea since I rescued him about 3 weeks ago.  He urinates and has diarrhea as soon as he eats and drinks water.  He has a healthy appetite, but drinks about 8 ozs. of water per day.  He has been off the antibiotic for 7 days, and his diarrhea is not getting better.  His urine and diarrhea smell like poison.  On the outside he looks healty, but. . .  

I was told to test his kidney/liver/urinary tract and his ears for mites.  I had his stool tested for parasites, and it came back neg., but I was told to test it again, as the eggs may not have hatched - what is that about?  

Answer
It sounds like he has ear mites and his ears need to be thoroughly cleaned and treated with the appropriate medication as there may be secondary infection in the ears as well as the mites.

The urine smell is because he is not neutered and will go away once he is neutered.

The diarrhea is most likely due to the antibiotics and his diet, and I would recommend feeding him a bland diet such as boiled chicken and rice with yogurt AND get him deworming.  Intestinal parasites can cycle anywhere from 2-3 weeks and eggs (what is detected on a fecal) are not always consistently shed in the stool, or if he was just infected, eggs won't show up right away on the stool sample.

His increased thirst is probably to compensate for the fluid he is losing in the diarrhea, but if the diarrhea resolves and he still drinks a lot, then I would recommend a chemistry screen to check kidney function.

If he was not tested for Feline Leukemia and FIV, he should have that done ASAP.