Feeding tubes are a low stress treatment method for chronic anorexia in cats. Fairly recently, Juliet stopped eating due to stress after surgery. She hates being handled by people, so I had the vet put in a feeding tube immediately and she was fine a week later. I believe that if we had tried to syringe feed her, it would have continued to stress her out (continuing the anorexia).
Dehydration
Dehydration can be easily treated with subcutaneous fluids, but a vet needs to examine the cat to be sure that there is not an underlying problem causing the dehydration.
If it's a Friday and your cat just stopped eating and your vet isn't available on the weekend, call you vet and ask for advice specific to your cat's health and any existing conditions.
What to Expect
The most common treatment for anorexia is appetite stimulants. This medication is often used in addition to treating whatever the underlying cause for the anorexia may be. For example, in the cat with sinus problems, we would often give him antibiotics for the sinus infections and appetite stimulants to get him started eating again.
Feeding tubes are a treatment method for chronic anorexia, or anorexia that has progressed into hepatic lipidosis. It can sometimes be used as a treatment method in other cases of anorexia as well. For example, after a surgery, Juliet stopped eating due to stress. She hates being handled by people (medications, syringe feeding, etc), so I had the vet put in a feeding tube immediately and she was fine a week later. I believe that if we had tried to syringe feed her, it would have continued to stress her out (continuing the anorexia).
If your cat is also dehydrated, the vet may administer subcutaneous fluids to your cat, or use an IV for more intensive therapy.
Your cat may need to stay overnight or at the vet's for several days if she is very ill (from anorexia, dehydration, or from the underlying cause).