If the cause of the diarrhea your pet's psychological, this is the easiest case, you need not worry much. Yes, cats can go liquid if they are disturbed, subjected to stress, somewhere, transported, invading their territory. You only need to eliminate the irritant and do not feed your pet during the day. Naturally, you need to provide the animal access to water and toilet. But on the street it is better not to start.
In cases where the cat diarrhea due to stale or too greasy food, to fasting especially hope not. This indigestion should be treated, otherwise it will result in dysbiosis. Give the animal dissolved in water activated carbon using a disposable syringe without a needle. In parallel, it is possible to give her a decoction of chamomile (heals) or oak bark (knits). Dosage – 10 ml 3 times a day. Copes well with diarrhea "Enterosgel". It not only normalizes the chair, but also excretes toxins. You can give more "Bifitrilak" or "Baktisubtil" to saturate the gut with bifidobacteria. There are also veterinary preparations, for example, "Vecoma 1.1".
However, if the diarrhea has not stopped during the day, and the cat feels bad, clearly weakening, it is urgent to go to the vet. Because the disorder can be caused by different types of toxic substances that she ate, or a virus. In this case, the delay can cost your pet's life. Any doubt is treated in favour of a trip to a specialist. It is better to err.
The vet need to show not only the sick animal, but a stool sample (for analysis), and also to tell about the frequency of the stool, its consistency.
If the feces of the cat is brown, it usually indicates the banal overeating, food poisoning or stress. But the light color of feces and stench, rather, talking about a viral infection.