yes my maltese demi had this as well. I had 2 fecals and a fecal culture done. We could not figure out what was going on but it cleared up and no issues since and has been 6 months now. We chalked it up to colitis as they can get blood in stool from that. Dh was gone to visit family a week and that triggered it and then second time it was after groomer came so think it was stress related.
sometimes giardia is hard to detect so ims said to do fecal once every week for 3 weeks to see if it shows up.
here are some pics on link below i know gross but i took to vet so have it so you can compare it.
DEMI POOP pictures by dwerten - Photobucket