Causes of blood in the urine

Patient: I just urineated and had blood mixed in with it.i had surgery on my lower back ,two disces removed an fused with a metal plate to hold in place.i was told by my dr. no lifting or bending,but walking was all rite. well today was my first day on treadmill ,i walked for twenty minutes .later i urineated and thats when i noticed the blood coming out . i would like to no what might have caused this??

Doctor: There are several conditions that can cause blood in the urine. These conditions include inflammation or infection of t he urethra (the tube that carries urine from the bladder through the penis), some bladder infections, bladder tumors, urinary tract stones and kidney tumors. This is not an exhaustive list. You should see a urologist who will first confirm that you are indeed passing blood in the urine and then will order the appropriate test to determine the cause. The test will range from analysis of the urine, urine culture and possible CT scan.