I had bladder cancer 15 years ago. i had a trace of blood inmy urine. the doctor scoped me and found no tumor. he sent my blood to get a full report. what else could be the cause of blood in urine?

Wait for evaluation: Wait for full report , it is good no visible tumor , always possible to have an early recurrence not seen by necked eye only by urine cytology , even if it is , possible to get rid of it. Speak to your doctor.

Several things: With a history of bladder cancer, recurrence would be a possibility. With a negative scope, this is less likely. Urinary tract stones, infection or prostate inflammation can also cause microscopic hematuria.