Dr. Bob Lind, one of the principal WS100 race physicians, told us a the prerace medical briefing that brown pee is a very dangerous sign, indicating that myglobin, a large molecule protein, is being released from damaged muscles, and can clog the kidney filters, resulting in acute kidney collapse, medevac by helicopter, dialysis, permanent kidney damage. The evaluation of brown urine during or immediately after extreme forms of exertion is critical. The discoloration can be caused either by blood or by myglobin a waste product that occurs with muscle tissue death. It is recurrent in some individuals and results in no long term problems. Once the diagnosed, individuals can continue the activity without need for further evaluation unless new symptoms such as burning with urination or unexplained back pain should occur.
Myoglobinuria is always a big problem.
Myoglobin is a big sticky molecule. The kidney is a filter. Too much myoglobin can permanently clog the filter. For the patient this translates to frequent visits to a dialysis center until a renal transplant becomes available - not a good deal. One of the biggest pitfalls is that many physicians are not well versed on the subject.