Hello there, sorry to hear elsie is not feeling well. As vets we generally try and tie in all the signs to one disease and the signs your dog is showing of jaundice, blood in stools and lethargy are most likely to all be associated with some type of haemolytic anaemia (destruction of red blood cells within the body). This can appear to begin quite suddenly. Other possibilities are liver disease and gastrointestinal disease (infections, inflammations, tumours). I would advise a vet visit asap firstly as she is clearly not feeling well and secondly becouse if it is haemolytic anaemia, the loss of red blood cells will make her weaker and weaker and can be fatal. If it is indeed this problem, she may need a blood transfusion and investigation as to the cause but please bear in mind we don't always find the cause any may need to treat symptomatically. Hope this helps and good luck!
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