Had dre / prostate exam and within 5 to 10 mins later had urinalysis. test positive for wbc. can dre cause wbc in urine in this case?

Possibly: in general, it is a good idea to do the urinalysis before a digital rectal exam of the prostate. It's impossible to know if the white blood cells would've been present in the urine if it is been checked before the prostate exam though. either way, I believe that the presence of white blood cells in the urine dictate a urine culture be performed

No: DRE would not have caused WBC in urine. Talk to your doctor about it as it may be due to infection in the prostate or urinary tract.