Constipated Cat but when she goes poop is HUGE and moist and smelly

Everything I read about constipation and cats talks about small dry hard feces.  Our cat has had this problem of not being able to go and straining (usually throwing up) and then straining some more until she gets out an almost human size stool that is moist and very smelly.

Before I see the vet and pay hundreds for tests, any advice?

We have added fiber to her hard food and changed both soft and hard food from lower quality brands to Blue recently.  This is an on again off again problem for probably over a year now.  Cat is 12 years old.

Thanks for your help!

i would suggest feeding all wet

I would read up on feline "MegaColon" - perhaps some folks here who have experience with cats with this condition can weigh in on the symptoms?

Right off the bat - I would definitely stop the dry food.  Encourage as much water drinking as possible.

Some fiber, expanding the stool, might not be good.  Miralax- tasteless and easily mixed in with wet food and a splash of water, is gentle and only holds water in their stool, making it easier to go.

But I don't know that your cat needs extra fiber - it may be making things worse?

But dry food - yea, can be pretty evil sometimes.

I always have good luck treating GI problems with slippery elm bark.  If it's related to a severe and chronic condition, that's something that will probably require testing and medication.  You can always give the SEB a shot and see if it helps.  1/8-1/4 teaspoon mixed with water (1 tablespoon per 1/4 t. SEB) makes a nice syrup that some cats will lap up without coaxing, but others will need it mixed with something yummy.  Try to give it at least an hour apart from supplements and 1-2 hours apart from meds.  It shouldn't be given regularly with food due to interference with mineral absorption.

She could have food sensitivities.  I would try kitty on a novel protein limited ingredient diet for a few months, see if that helps.  Nature's Variety Instinct is pretty much the go-to for this purpose.  Novel proteins are any meat that isn't commonly found in cat food, and you want to be sure it isn't used in conjunction with a common protein like chicken, turkey, beef or fish.  

When you say you are adding extra fiber, what are you adding?  That could be the reason she is producing such a large stool.

I would also suggest you try to add as much water to her diet as possible, (all canned food if possible) and give her Miralax (1/8 to 1/4  teaspoon), and see what happens.  I, personally haven't tried the Slippery Elm Bark for constipation, but have heard of others doing so.