Hogdog Ellis presents at your clinic because he just 'isn't runnin' them hogs like he should be, Doc.' The situation started yesterday. He had been on a 4-day hunting trip 10 days prior and he ran very well. The owner noticed the dog has been very droopy and his urine has been dark. On presentation, Ellis' temp was 104.5, P and R very elevated. His abdomen was painful on palpation as was his thoracolumbar and midlumbar spine. He has dark, reddish-brown urine. What disease should be high on his list of differentials