Andrew Siegel MD 2/11/17
This entry is a brief overview of bladder anatomy and function to help you better understand the two most common forms of urinary leakage—stress urinary incontinence and overactive bladder— topics for entries that will follow for the next few weeks. Having a working knowledge of the properties of the bladder will serve you well in being able to understand when things go awry.
Drawing of the bladder and urethra by Ashley Halsey from “The Kegel Fix: Recharging Female Pelvic, Sexual and Urinary Health”
The bladder is a muscular balloon that has two functions—storage and emptying of urine. The stem of the bladder balloon is the urethra, the tube that conducts urine from the bladder during urination and helps store urine at all other times. The urethra runs from the bladder neck (where the urinary bladder and urethra join) to the urethral meatus, the external opening located just above the vagina.
Bladder Control Issues—More Than Just a Physical Problem
Urinary incontinence is an involuntary leakage of urine. Although not life threatening, it can be life altering and life disrupting. Many resort to absorbent pads to help deal with this debilitating, yet manageable problem. It is more than just a medical problem, often affecting emotional, psychological, social and financial wellbeing (the cumulative cost of pads can be significant). Many are reluctant to participate in activities that provoke the incontinence, resulting in social isolation, loss of self-esteem and, at times, depression. Since exercise is a common trigger, many avoid it, which can lead to weight gain and a decline in fitness. Sufferers often feel “imprisoned” by their bladders, which have taken control over their lives, impacting not only activities, but also clothing choices, travel plans and relationships.
Bladder Function 101
Healthy bladder functioning depends upon properties of the bladder and urethra. Bladder control issues arise when one or more of these go awry:
The average adult has a bladder that holds about 12 ounces before a significant urge to urinate occurs. Problem: The most common capacity issue is when the capacity is too small, causing urinary frequency.
The bladder is stretchy like a balloon and as it fills up there is a minimal increase in bladder pressure because of this expansion. Low-pressure storage is desirable, as the less pressure in the bladder, the less likelihood for leakage issues. Problem: The bladder is inelastic or less elastic and stores urine at high pressures, a setup for urinary leakage.
There is an increasing feeling of urgency as the urine volume in the bladder increases. Problem: The most common sensation issue is heightened sensation creating a sense of urgency before the bladder is full, giving rise to the frequent need to urinate. Less commonly there exists a situation in which there is little to no sensation even when the bladder is quite full (and little warning that the bladder is full), sometimes causing the bladder to overflow.
After the bladder fills and the desire to urinate is sensed, a voluntary bladder contraction occurs, which increases the pressure within the bladder in order to generate the power to urinate. Problem: The bladder is “under-active” and cannot generate enough pressure to empty effectively, which may cause it to overflow when large volumes of urine remain in the bladder.
A bladder contraction should only occur after the bladder is reasonably full and the “owner” of the bladder makes a conscious decision to empty the bladder. Problem: The bladder is “overactive” and squeezes prematurely (involuntary bladder contraction) causing sudden urgency with the possibility of urinary leakage occurring en route to the bathroom.
The bladder and urethra are maintained in proper anatomical position in the pelvis because of the pelvic floor muscles and connective tissue support. Problem: A weakened support system can cause urinary leakage with sudden increases in abdominal pressure, such as occurs with sneezing, coughing and/or exercising.
In cross-section, the urethra has infoldings of its inner layer that give it a “snowflake” appearance. This inner layer is surrounded by rich spongy tissue containing an abundance of blood vessels, creating a cushion around the urethra that permits a watertight seal similar to a washer in a sink. The female hormone estrogen nourishes the urethra and helps maintain the seal. Problem: With declining levels of estrogen at the time of menopause, the urethra loses tone and suppleness, analogous to a washer in a sink becoming brittle, potentially causing leakage issues.
The urinary sphincters, located at the bladder neck and mid-urethra, are specialized muscles that provide urinary control by pinching the urethra closed during storage and allowing the urethra to open during emptying. The main sphincter (a.k.a. the internal sphincter) is located at the bladder neck and is composed of smooth muscle designed for involuntary, sustained control. The auxiliary sphincter (a.k.a. the external sphincter), located further downstream and comprised of skeletal muscle contributed to by the pelvic floor muscles, is designed for voluntary, emergency control. Problem: Damage to or weakness of the sphincters adversely affects urinary control.
The main sphincter is similar to the brakes of a car—frequently used, efficient and effective. The auxiliary sphincter is similar to the emergency brake—much less frequently used, less efficient, but effective in a pinch. The pelvic floor muscles are intimately involved with the function of the “emergency brake.”
The seemingly “simple” act of urination is actually a highly complex event requiring a functional nervous system providing sensation of filling, contraction of the bladder muscle and the coordinated relaxation of the sphincters. Problem: Any neurological problem can adversely affect urination, causing bladder control issues.
A reflex is an automatic response to a stimulus, an action that occurs without conscious thought. There are three reflexes that are vital to bladder control:
Guarding Reflex: During bladder filling, the “guarding” (against leakage) pelvic floor muscles contract in increasing magnitude in proportion to the volume of urine in the bladder; this provides resistance that helps prevent leakage as the bladder becomes fuller.
Cough Reflex: With a cough, there is a reflex contraction of the pelvic floor muscles, which helps prevent leakage with sudden increases in abdominal pressure.
Pelvic Floor Muscle-Bladder Reflex: When the pelvic floor muscles are voluntarily contracted, there is a reflex relaxation of the bladder. This powerful reflex can be tapped into for those who have involuntary bladder contractions that cause urgency and urgency leakage.
Wishing you the best of health,
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Dr. Andrew Siegel is a practicing physician and urological surgeon board-certified in urology as well as in female pelvic medicine and reconstructive surgery. Much of the content of this entry was excerpted from his recently published book The Kegel Fix: Recharging Female Pelvic, Sexual and Urinary Health: http://www.TheKegelFix.com
He is also the author of MALE PELVIC FITNESS: Optimizing Sexual & Urinary Health http://www.MalePelvicFitness.com