Warning TMI--Blood in urine

So I know this is really gross, but I just have to ask.  I am marathon training and finished my last 20 miler yesterday.  Considering that I am very slow, this takes me a long time--like 4 hours 12 minutes long.  Anyway, hours after I finished my run, I went to the bathroom for the first time and noticed that my urine was very bloody.  I have had this in the past with a kidney stone, so I figured it was another kidney stone.  My husband told me I should look online to see if dehydration could maybe cause it, and I found some things that really freaked me out that had to do with blood in the urine after running long distances.  Being the paranoid person I am, I ended up getting it checked out, and spent the entire night at the hospital.  Kidneys checked out fine, myoglobin was high but not alarmingly high, etc.  They are just chalking it up to all the jarring around from running causing trauma and bleeding.  Have any of you had this before?  I have done other long runs and never had this problem before.  I am just curious if you have experienced it and what you were told.