Have had severe pain in my back x4 days. Ct shows both a 3mm bulge and hydronephrosis in r kidney (report says r kidney larger than l). Urology denied my referal my dr sent, said to them kidneys look normal. What should I do?

Second opinion. Can you get a second opinion? It is not unusual for a urologist to have a difference in opinion regarding a ct scan. There are some conditions such as an extrarenal pelvis which are variants of normal. The radiologist may call it hydronephrosis whereas the urologist may not. The urologist should not have denied your consultation with them and explain to you why they feel the ct is normal.
Interesting... Does the radiologist's report specifically say there is hydronephrosis, or is this your primary care doctor's own interpretation? If the latter, I would side with the urologist, as he/she is generally more adept at reading imaging studies of the kidneys. If the radiologist said there is hydronephrosis, I am very surprised that a consulted urologist would refuse to see you.