Urinary retention can be defined as the inability to pass urine.
Occasionally patients are able to partially empty and this is described as incomplete bladder emptying. Usually this is thought to only occur in male patients but can occur in both sexes. The cause for retention in men differs from that in women.
In men, enlargement of the prostate (BPH or benign prostatic hyperplasia) is the most common cause of urinary retention. The prostate grows enough to block urine flow out of the bladder and retention results. Strictures, or scarring of the urethra can lead to retention of urine. Bladder stones can fall into the bladder neck and cause obstruction. Rarely, a large bladder tumor could block the bladder outlet. Occasionally, medications such as decongestants and antihistamines can cause transient obstruction of urine flow by closing the bladder neck muscle or slowing bladder muscle activity. Severe spinal stenosis or compression of the spinal cord could lead to progressive or sometimes acute onset of retention. Severe constipation can lead to reflex bladder relaxation.
Women usually develop urinary retention after surgery to correct leakage of urine. With vaginal sling procedures for incontinence, the sling may be to tight against the urethra partially or completely blocking urine flow. Bladder neck suspension surgery can lead to overcorrection of the bladder neck and urethra leading to urinary retention. Significant vaginal wall prolapse, especially anterior vaginal wall prolapse can lead to urethral kinking and difficulty with emptying. Urethral stenosis, or scarring of the opening of the urethra can progress slowly to cause retention. Fortunately, a rare cause of urinary retention can be urethral cancer. Large bladder tumors, as in men, can block the bladder outlet and lead to retention. Although rare, women can see similar issues with bladder emptying as men when taking antihistamines and decongestants. Though seen in men as well yet more common in women, multiple sclerosis and other types of brain injury can lead to urinary retention.
Both men and women can have idiopathic non-obstructive urinary retention. This name implies an inability to empty the bladder but no obvious obstructive source is noted. These patients frequently have some inciting event such as surgery (perhaps in the pelvis but often in other parts of the body) or emotional stress. The cause is unknown but is suspected to be an abnormal neurologic response to the inciting event. This does not suggest these patients have neurologic injury but that they possibly have discoordination of neurologic events.
A good history can often give good insight into the cause of the retention. New medications, recent surgery, past urethral trauma, recurrent bladder infections, blood in the urine a just a few historical items that may give a hint as to the direction to look for a cause of retention. The physical examination can reveal an enlarged prostate, urethral irregularities, vaginal prolapse, impaired neurologic reflexes and sensation, overcorrection of the anterior vaginal wall and impacted stool suggesting an etiology for retention. Evaluation of bladder volume with a bladder scanner or by passing a bladder catheter gives an idea of how severe the retention has become. Urine is usually evaluated as many of these patients with retention will develop bladder infection. Cystoscopy can be performed to evaluate for urethral stricture, prostate size, bladder stones or bladder tumors. Occasionally X-rays of the urethra and bladder can reveal urethral stricture or show the severity of bladder prolapse. Ultrasound of the kidneys, CT scan of the abdomen and pelvis and IVP are often obtained to rule out dilation of the ureters or kidneys from high bladder pressure. A urodynamic evaluation is often performed to show the actual problem with bladder function that leads to retention.
If the urinary retention is acute and leading to severe discomfort, immediate relief is obtained from a bladder catheter often referred to as a Foley catheter. This will drain urine until the source of the retention is identified and treated. If long-term drainage is necessary the catheter can remain in place with monthly changes. Patients or caregivers can learn to intermittently catheterize the bladder so that a chronic indwelling catheter is not necessary. Occasionally medications can be given to relax the bladder neck contraction to aid in passage of urine. Flomax, Cardura, Uroxatral and Hytrin are medications known as alpha-blockers that can provide modest relief for patients with difficulty emptying. Discontinuation of antihistamines or decongestants may improve upon the ability to empty. If anatomic issues such as an enlarged prostate, urethral stricture, urethral stenosis, urethral cancer or bladder tumors are suspected, surgery will be necessary to correct the issue leading to retention. If obstruction is related to an overcorrected urethra or bladder neck from incontinence surgery, incision or loosening of the sling and/or urethrolysis may be necessary to relieve the obstruction. If idiopathic non-obstructive urinary retention is diagnosed, initial attempts with biofeedback may improve voiding. In those patients who fail biofeedback, sacral nerve stimulation can initiate voiding in a large number of patients.