A cause of stress urinary incontinence in which the urethral sphincter is unable to contract and generate sufficient resistance in the bladder, especially during activities that increase pressure on the bladder (e.g. coughing, laughing). ISD may be due to congenital sphincter weakness, such as myelomeningocele or epispadias, or it may be acquired from prostate cancer treatments, trauma, radiation therapy, or spinal cord injury.