I've been taking drugs for OAB for so long with no use, during a urodynamic study i couldn't be catheterd. would a stricture be the cause of nocturia?
Structure is possible
If the medication you have been using for overactive bladder has been of little help, then it is important to consider causes of nocturia which may be structural rather than neurological or due to musculature problems.
At this point, the ideal way to proceed would be to have non-invasive imaging and urodynamic testing performed by a urologist.
FREQUENT NIGHTTIME URINATION