Can a fecal exam be wrong?

I just adopted an adult female cat from someone who has more of a "farm atmosphere". I didn't know much about the cat and I was pretty concerned about worms. So, when I took her to the vet they did a fecal exam and said that she was perfectly healthy and the fecal exam was negative for parasites. However, I still see little white things on her bottom a few days ago and she keeps throwing up. Could the fecal exam have been wrong? Could it be something the fecal exam just couldn't pick up? I know I'm not imagining things because my husband saw it too... Please help. I really can't spend the money to take her to the vet again unless she really needs it. Not to mention the traumatic car ride!

If the white things look like grains of rice, they are probably tapeworm segments. From what I've heard, tapeworms don't show up in a fecal exam most of the time. They can be cured pretty easily with a dewormer from the vet. Since it hasn't been very long, you could probably get the medication without taking her in, but be sure that you ask them about checking her for dehydration--if she's been throwing up for a few days, she could be dehydrated already.

Tomas had been in to see the vet 3 times, each time I asked whether his stinky gas could be from worms, parasites, or bacterial infection. It wasn't till yesterday, his 4th visit, for neutering that she realized he had tapeworms.
Though to be fair there were no outward signs (segments around the butt or in the stool), no bloating and gums looked fine, so I wasn't sure either.

Yes it is possible for a fecal exam to be wrong, in fact it can be pretty common, which is why vets will sometimes ask for several fecal samples before a diagnosis can be positively made. If it is tapeworms that your kitty has, and it sounds correct, then that is one of the few worms that do not show up in a stool sample. But you also have to remember that stool samples are taken from a very small portion of a sample-not the whole thing, so it is possible that the sample that we choose does not contain the problem worm or bacteria but if another sample was taken from another section of the stool then that could be the one that contains the information-it is always a russian roulette to see if you get the right part of the stool. If you can it is always a good idea to take a sample of the worm that you are seeing in a plastic bag or container to the vet as well that alone will sometimes prove more effective than a stool sample itself.

I had that exact same thing happen to me - I saw the worms myself in the stool and saved it over the weekend to take to the vet. They called me back and said there was no evidence of worms - microscopically. I aasked if they had LOOKED at the sample, LOL. But when I described it, they gave me the medicine anyway, especially since there had been a history of fleas.

Ben had fleas when we found him. We tok over two samples and they were both clean. What would happen to my kitties if they did have worm & I didn't know? I don't see anything in their poop or butt. I wonder cause I never had a cat with fleas and no worms.

Well, I didn't know about the fact that tapeworms don't show up on the micro exam - that's interesting. I don't know that much about worms, but your kitty would have a big belly, and probably would lose weight because of not getting enough nutrition. And also be hungry all the time.

Well they are fat & always hungry
I wish they would lose some weight.

Thanks I have been worrying about this for the past few days. I wasn't seeing Lucky go poop. He normally stinks me out of the room. I finally saw him today and clapped.

Well thank you all. I would have felt dumb calling the vet without your help. However, they still haven't called me back to get the medicine! They aren't nearly as grossed out by this as I am! Thank you all again.