Blood In Urine

To go along with my prior posting, for over a month now my father has had blood in the urine. Some days it is every time he urinates, other days it is intermittently. Several days ago, it all together stopped but then it started again. The blood isn't diluted, rather, the initial stream is all blood. Either a couple of drops or one second or so of the initial stream. Thereafter, it is all urine.
After urine tests, a CAT scan of the abdomen and pelvis, nothing has shown up. New urologist is recommending a cystoscopy to check the urinary tract, prostate, and bladder. The urologist seems to think that the cancer has spread to the bladder. But to me it doesn't make sense. If it was the bladder then the entire urine would be diluted with blood, not the initial stream. To me it seems like the blood is coming from outside of the bladder, somewhere in between the bladder and prostate.....maybe in the urinary tract possibly.

Since my father is on coumadin for a history of phlabitis and pulmonary embolism, we believe the bleeding may have something to do with his intake of coumadin. However, even lowering it to 1.5 mg a day hasn't helped. For a while we thought it may have something to do with iron supplements he takes because he is so anemic. We stopped that but it did not prevent the bleeding. I read on a website that in rare cases, bleeding may occur with pain killers such as Oxycodone and Vicodine that he is taking. Anyways, to date we have not figured it out and we want to try other things before a cystoscopy. Any suggestions, ideas, references, etc. will be helpful.