Peeing blood is a problem that happens for some of us when we play drums too hard. Stanford did a study on drummers who peed blood and also long distance runners who also peed blood and said it is from the break down of cells in the hand (or foot) being passed too quickly through the kidneys.

Fo me the problem is simply about playing too hard..it starts with the mental (not being relaxed), not breathing deeply, being stressed about the other drummers or dancers ..
If you are peeing blood when you are soloing on djembe and not when you are playing accompaniment this is important to remember.

The concept of phrasing and leaving space in between your musical (drum) notes is very important for not peeing blood as well…You have to leave a lot of space between phrases..Sometimes when I play in Oakland it is hard to leave too much space in between notes because someone will “drop in” (start their solo) if I leave a lot of space. It can be frustration.

It is the hardest yet easoest thing to do once you really grasp the concept. Play a phrase even one you make up and STOP..Play another and STOP..and..when you are really in a flow..ride the rhythm..on top of it so you are floating, like you catch a wave, the wave pushes you, you ride it, you do not pull it or push it, you only push to get into it, once you are in the groove, the tube, it pushes you. So the key is to catch the ryhtym in the middle, in the place where it actually pushes you along. The peeing blood comes from stress on the bod when you have not caught the rythym..