Welcome babygirl, we are just sorry why you are here. The 2 primary tests for bladder cancer is a cystoscopy and CT scan. Both are very useful with the scope usually the more conclusive in conjunction when used in a biopsy.
The ER Doc was probably concerned with many possibilities so don't be too harsh on him/her in doing a CT scan. They may have been concerned with other internal issues such as kidney stones, cancer of the kidney among many other internal problems. Sometimes a "papillary" mushroom like tumor will be picked up on a CT Scan. There is also a flat (called CIS) rash like tumor that cant be seen. IF they saw a papillary like stalk it MAY or NOT be cancer. There are other types of growths. The ER doctor may have simply wanted to prepare you for the cancer possibility. You won't really know much until the scope and if that is found a biopsy will be scheduled called a TURB (transurethral resection of the bladder). Usually it is a short surgery under anesthesia with a biopsy done with results usually in 4-10 days. So, you really won't know much until then. It is "one day at a time", that is all you can control!
Either way, this is treatable and beatable. Keep posting with questions, someone will be able to help give insight.