Urinary incontinence is the involuntary loss of urine. Overflow incontinence is unique because it is not caused by a sudden urge or physical strain, but by the bladder’s inability to empty properly. This condition stems from a persistent state of chronic bladder overfilling. This article explores the mechanisms, causes, diagnosis, and management strategies for overflow incontinence.
Defining Overflow Incontinence and Its Mechanisms
Overflow incontinence is the involuntary leakage or dribbling of urine that occurs when the bladder is chronically overfilled and cannot empty completely. This failure to fully discharge contents is known as urinary retention. Retention causes the bladder to become distended, holding an abnormally high volume of urine over time.
As the bladder fills, the internal pressure steadily increases until it exceeds the resistance of the urethral sphincter. This pressure forces a small amount of urine past the sphincter, leading to constant or frequent dribbling. This frequent loss of small volumes is the hallmark symptom.
Because the bladder never fully empties, individuals often feel the need to urinate immediately after voiding. This incomplete emptying is accompanied by a weak urine stream, difficulty initiating urination, and frequent voiding of small amounts. Nocturia, the need to wake up multiple times during the night, is also a common symptom.
The primary physiological issue is that the detrusor muscle, which contracts to push urine out, either cannot contract strongly enough or faces too much resistance. When the detrusor muscle is impaired, it leads to underactivity and a loss of effective contraction.
Underlying Causes
Physical Obstruction
In men, the most common cause is benign prostatic hyperplasia (BPH), where the enlarged prostate gland presses on the urethra. This physical blockage prevents the free flow of urine, resulting in a buildup of residual volume. Other mechanical obstructions include urethral strictures, bladder stones, and tumors. In women, a severe pelvic organ prolapse can physically compress the urethra, creating a similar obstruction.
Neurological Impairment
The second major category involves damage to the nerves controlling bladder function, which compromises the detrusor muscle. Conditions like poorly controlled diabetes can lead to diabetic cystopathy, impairing bladder sensation and muscle contraction. Other neurological disorders, including multiple sclerosis, Parkinson’s disease, and spinal cord injuries, disrupt the signaling pathway between the brain and the bladder.
Medications
Certain medications can also contribute by interfering with bladder contractility or increasing outlet resistance. Anticholinergic drugs, used for conditions like overactive bladder, and some opioid pain medications can relax the detrusor muscle or tighten the sphincter. Identifying and adjusting these medications is necessary for determining the root cause.
How Doctors Diagnose
Diagnosis begins with a detailed review of medical history, including medications, and a physical examination. The physician checks for a distended bladder and looks for neurological issues or physical obstructions, such as an enlarged prostate.
The most important step in confirming overflow incontinence is measuring the Post-Void Residual (PVR) volume. PVR volume is the amount of urine remaining in the bladder immediately after the patient attempts to empty it. It is measured using a non-invasive bladder ultrasound or by inserting a temporary catheter. An elevated PVR volume strongly indicates chronic urinary retention.
To identify the underlying cause, doctors may recommend urodynamics testing. These tests evaluate bladder and urethra function by measuring pressure, volume, and flow rate during storage and voiding. A pressure-flow study is useful for distinguishing between a weak detrusor muscle and a physical obstruction.
In some cases, a cystoscopy may be performed. This involves inserting a thin, lighted tube into the urethra to visually inspect the bladder lining. This procedure allows the physician to directly identify physical obstructions, such as urethral strictures, bladder stones, or prostate enlargement.
Treatment and Management Options
Effective treatment depends on addressing the specific underlying cause, whether obstruction or weak bladder muscle. For cases caused by bladder outlet obstruction, such as BPH, surgical intervention is often the most definitive solution. Procedures like transurethral resection of the prostate (TURP) remove obstructive tissue, relieving pressure on the urethra and allowing the bladder to empty more efficiently.
Catheterization
When chronic retention cannot be resolved by surgery, the most effective management strategy is clean intermittent self-catheterization (ISC). This involves the patient regularly inserting a thin, flexible tube multiple times a day to completely drain the bladder. ISC prevents dangerous pressure buildup and is preferred over a permanent catheter due to a lower risk of urinary tract infections.
Medications
Medication plays a role in managing underlying conditions. For men with BPH, alpha-blockers like tamsulosin are prescribed to relax smooth muscle tissue in the prostate and bladder neck, improving urine flow. In cases of detrusor muscle underactivity, a cholinergic agonist medication such as bethanechol may be used to increase the contractility of the bladder wall.
Behavioral Management
Supportive measures, including behavioral and lifestyle changes, are also incorporated into the management plan. Timed voiding schedules encourage the patient to attempt urination at set intervals, preventing the bladder from becoming overly full. Techniques like double voiding, where the patient waits briefly after voiding to try again, help reduce the residual volume.