Some of the causes of OAB can be
Urinary tract infection,
medications such as diuretics, neurological disease (parkinsonism, MS), tumors of the urinary tract, nerve damage caused by trauma to the abdominal area or pelvis or prior surgery, stress incontinence - associated with weak pelvic floor muscles.
Diagnosis is done by medical history, examination and investigations such as urodynamic testing multichannel, or subtracted, cystometrogram. cystoscopy, imaging tests etc.