Just as with humans, treatments for feline constipation depend on the cause of the condition and the condition of the cat. Again like humans, those most vulnerable are the elderly and those who have trouble eating, and they also have to be treated carefully for fear of causing worse trouble.

Because cats are "pure" carnivores, their digestive tract is very short, as it is not designed to process vegetable fibre. Also, cats have a strong vomit instinct (as I'm sure you've noticed), so when they eat something inappropriate, they usually cough it up promptly. So constipation is a sign that several aspects of the patient's digestive system are not up to par, and therefore worthy of a vet's attention.

Sorry it's so expensive.

Let me tell you about Cecil, a delightful little black tomcat cat who developed pancreatic disease and stomach ulcers, thus lightening my wallet of a couple of thousand bucks before popping his clogs and breaking my heart. The diagnosis was made on necropsy. And then there was Alexander the Great, a large biscuit-coloured individual who died of kidney failure caused by crystaluria after several hideously expensive treatments that did absolutely no good at all.

Cats. One way or another, we pay for the privilege of their company.