Cat black stool. Further steps?

Hi all, My 14 y/o cat has been having stool issues for the past couple of weeks. We've been to the vet four times trying to get it under control and I'm not sure if we're moving in the right direction or not. She's currently on FortiFlora and a painkiller (as needed) and eating food for digestion. Up until two days ago, her stool had been pretty formless and mushy, like it had been stepped on. I saw a little blood in it two weeks ago which is what started the vet visits. As of yesterday, the form of the stool looks MUCH better, coming out in well-defined turds. But now they're black and shiny on the outside, though normal looking on the inside. I did a little googling and some posts describe that as blood while others say it can happen if it's just old poop that's been sitting in there for a while. Behavior-wise, she's been pretty normal. Great appetite (loves the digestive food), very affectionate and chatty, peeing normally. One weird thing is that I got her a second litterbox and she tried to eat the litter (World's Best), though she treats the other litterbox totally normally, so I'm not sure if it was just the litter smelling good or what. She's had an x-ray, urinalysis, and blood panel done in the past week, none of which have shown any issues. She also had a stool sample looked at during the first visit, and had no signs of parasites or anything like that. I'm going to call the vet when they open, but I'm wondering what next steps would even be? I'm almost positive this all started due to stress when I was out of town for a couple of days, and I can't imagine the repeated visits to the vet have done much to settle her stomach. Idk, just tired of being worried. Any advice is appreciated!

Hello - black stools can be extremely serious and should be presented right away to your vets, even though your cat was obviously examined very recently.  This is because black faeces represents bleeding into the gut.  This can be a side effect of some medications, especially if the dose has been incorrect or there is some underlying tendency not to clot.  The most common medications to cause bleeding through gastrointestinal ulceration are steroids and non-steroidal anti-inflammatories.  Different concerns might include consuming rats that have eaten poison or ever cancer.  The feeding of activated charcoal can also cause extremely black poo, but you'd know if that was the case.  Sometimes, acute trauma, foreign bodies or Addisons can be involved.   Sometimes, when cats are poorly e.g. with cancer, they will feel extremely hungry and will eat interesting things to try to make up for it - so the excessive consumption of cat litter is worrying me too.  Please treat this as a relative emergency.  Hopefully, looking at the time and date of your post, you will have done so by now - how did you get on?

Hello - black stools can be extremely serious and should be presented right away to your vets, even though your cat was obviously examined very recently.  This is because black faeces represents bleeding into the gut, which cannot be seen from the outside on examination (hence your vet will not have seen this damage).  Malena (black faeces) can be an unpleasant effect of some medications, especially if the dose has been incorrect or there is some underlying tendency not to clot.  The most common medications to cause bleeding through gastrointestinal ulceration are non-steroidal anti-inflammatories.  Different concerns might include consuming rats that have eaten poison or ever cancer.  The feeding of activated charcoal can also cause extremely black poo, but you'd know if that was the case.  Sometimes, acute trauma, foreign bodies or Addisons can be involved.  When cats are poorly e.g. with cancer or liver disease (which can affect clotting facts), they frequently feel extremely hungry and will eat interesting things to try to make up for it - so the excessive consumption of cat litter is worrying me too.  Please treat this as a relative emergency.  Hopefully, looking at the time and date of your post, you will have spoken to your vet by now done so by now.  How did you get on?

Thank you for the reply! I spoke to the vet and it was suggested that it may be the diet change plus the painkiller that's causing the discoloration. I'm going to be bringing in a stool sample (when she next provides one). Also, to clarify the litter point, she hasn't been consuming it excessively. She only tried to eat it once and I stopped her.   Thank you once again!