Sometimes people can not empty their bladder because the bladder muscle has failed, (detrusor failure or underactive bladder). This can be the result of disease affecting the spinal cord or nerves to the bladder or damage to the bladder muscle but in many patients the cause is unknown. Patients may need to pass a catheter intermittently to empty their bladder or have a urethral or supra-pubic catheter (tube) permanently draining the bladder into a bag. In some patients where there is not a blockage and the bladder doesn't work, a device can be implanted to get the bladder working again so they can then empty the bladder without a catheter. This device is called Sacral Nerve Neuromodulation. The first step is a trial with a lead to the sacral nerves to test the therapy to see if it works. If the trial is sucessful the next step is implanting the device.
Occassionaly medication to relax the urethra can assist with a slow urinary flow or mild problems with bladder emptying but generally medication is not enough to help people with significant bladder emptying problems except when it is due to blockage from prostate enlargement. Medications can help in men to reduce the effect of prostate enlargement (BPH) which is restricting the flow of urine.
In some patients problems with the pelvic floor and urinary sphincter mean these structures do not relax to allow the release of urine. Continence physiotherapists and Continence Nurses can assist with behavioual therapy and pelvic floor relaxation to improve bladder emptying.
In some people urinary retention is the result of previous surgery such as stress incontinence surgery where a sling is placed but it is too tight. This can be reversed in some people by surgery to release (cut or remove) the sling.