Our poor Cavalier King Charles suddenly produced explosive diarrhoea last night that looked like jam! All over the kitchen - she turned round in circles as she was doing it and it sprayed everywhere! DH cleaned it all up, set off for bed through the dining room and found she'd originally been in there and done it too. 
I phoned the vet at 4am thinking she might evacuate her entire insides by morning, but he said she'd be ok till morning. There was more blood all over the kitchen floor this morning. Today she's been admitted on a drip, being kept in overnight and a sample has been sent off for analysis.
In 35+ years of dog owning I've never seen anything like it. It's some form of haemorrhagic gastroenteritis. Anyone else's dog had this?