Trigger has a show of blood if he gets stressed, or if he's loose - and quite a bit in the latter case too
the first time was when he went to be neutered, and the vet checked him out before he would operate, but there was no underlying condition
and it's happened again occasionally over his nearly 9 years, but it always stops again before I start to think of the vet - which would exacerbate the bleeding anyway as he hates the carrier
so hopefully once checked you can stop worrying