We've just had a second episode of our older, spayed female Lab leaving drops of blood from her urethra area.  I say area because the blood does not seem to be in her urine.  The first time this happened was last winter and it was easy to see that a few drops of blood fell on the snow when she squatted to pee.  Her urine appeared to be normal with no sign of blood in it.   I know I can't tell for sure just by looking but the funny little episode cleared up before I could get a urine sample in to the Vet. 

Since it was winter we thought perhaps she'd cut herself on a sharp piece of ice.  She goes off the path into the snow to pee and could have broken through the crust.  Or a sensitive part of her could have stuck to the ice and a little piece of skin ripped off when she moved.  She also left a few drops of blood on her bed and the floor when not urinating but always after getting up, leading us to suspect a funny little injury even more, one which opened up after she moved.  The drops were up to about an inch in diameter and only a few each time.

Another funny little blood episode seems to have cleared up.  No snow now so we wonder, did she squat on a blackberry thorn?  Get jabbed by a sharp stick?  Has anything like this ever happened to your girl?  I guess this could happen to the boys too, if they squat or even move the wrong way against a sharp branch.

I wouldn't put this down to coincidence I would have her checked by the vet.  It could be many things and it may have continued or appeared between these two episodes and you have missed it.

I have little dogs and none have ever injured themselves piddling. They don't go that low to the ground.

I can't imagine the same "accident" happening twice - think of the odds on that one!

I would get her checked by a vet, taking a urine sample, even if you can't see any more blood there may still be traces in the urine due to infection/problems in the bladder.

Hope she's ok.