An astronaut was carrying out an ultrasound on their own body as part of a new study, guided in real time by a specialist on the ground. A similar test before the astronaut launched to space had come back normal. But now the scan showed a clump of blood. Source 4n.
You Can Get Blood Clots From Space Flight (Hover)
The little bit that I've learned about this which I'm not sure is correct or not, but it's said to have something to do with the change of gravity to your body and the flow of the blood. Pretty crazy stuff.