bright red blood in poo

[hackneyzoo]

My lovely 10 year old dog has had red blood in his poo over the weekend. He is straining to go and the last week his stomach has been making lots of odd gurgling noises.
He is eating as normal and is behaving as normal. He's a mongrel rescue dog about the size of a lab. I'm going to take him to the vet first thing but any ideas what would cause this?
He also has lots of lumps on his tummy which the vet said were probably just fatty lumps that older dogs get. Now I'm worried it's something more sinister

Don't know but sending hugs. Hope he's ok.

My website had this when I foolishly changed his food, it sounded like a train going through him and the wind! The fresh blood appeared on day 4, the vet said it was gastritis and the bland food and probiotic combo would sort it out. Which it did, he was perfectly normal throughout except spinning round to gaze suspiciously at the noises coming out of him! It was alarming though.

Westie not website.

I think it can be a sign of colitis.