Have Cat Questions? Ask a Cat Vet Online.
Hi this is Dr. Hill. Please give me a moment to type my full response. Thank you.
Dark green stools can be a sign of a resolving intestinal bleeding. If there is an active hemorrhage in the intestinal tract then the stool is black, but then becomes green once active bleeding stops. It is important to have a fecal exam at your local veterinary hospital, especially since he goes outdoors and has some diarrhea. If you are not able to get to a vet in the next couple of days, then you can put him on probiotics to help support the bacterial population in his gut. I like Proviable or Fortiflora, both of which are available online. If the diarrhea is caused by parasites, then a fecal exam will tell you which medication needs to be used. Please ask any follow up questions. You can continue posting on this thread for a couple of days, even after rating my response. take care.
here is a link to the provable. https://www.chewy.com/nutramax-proviable-kp-dog-cat/dp/101468