Urinary incontinence: Pathology review

Definitions & Key takeaways

Urinary incontinence is a common condition that occurs when urine involuntarily leaks from the bladder, often through the internal and external sphincter muscles. There are several types of urinary incontinence, including urge incontinence, stress incontinence, and overflow incontinence.

Urge incontinence is typically caused by an overactive bladder, which can lead to sudden and strong urges to urinate that are difficult to control. Stress incontinence, on the other hand, is often due to increased pressure on the bladder, which can happen during physical activity, sneezing, or coughing. Overflow incontinence is caused by incomplete emptying of the bladder, leading to urine leakage due to bladder overfilling.

The treatment for urinary incontinence depends on the underlying cause and severity of the condition. Some common interventions include strengthening the external sphincter muscle by doing things like Kegel exercises, and catheterization or medications like alpha-blockers, which relax the smooth muscle to assist with urination.

Chapters:

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Case Study0:00–0:46

In the Urology ward, two people are coming in. The first is Oleg, a 70 year old man who says that he frequently has to use the bathroom and also complains of a weak urinary stream.
The second is Samantha, a 55 year old woman who says that she “pees” a little when she laughs. Samantha also has 2 children and both were born by vaginal delivery.
Now, both these individuals seem to have urinary incontinence. Urinary incontinence is a problem where the process of urination happens involuntarily, meaning that a person might urinate without intending to.
This is particularly problematic because it affects a person’s personal hygiene as well as their social life in a way that can be very limiting.Let’s talk about physiology real quick.

Physiology0:46–3:13

Okay, so as urine flows from the kidneys into the bladder, the bladder starts to fill. Lining the bladder is a layer of transitional epithelium containing “umbrella cells”.
These cells physically stretch out as the bladder fills, just like an umbrella opening up in slow-motion. This expansion is further aided by the relaxation of the muscular layer within the bladder’s walls, called the detrusor muscle.
At some point, the bladder fills up with urine that will eventually exit the body through the urethra. Now, the urethra is wrapped up in some muscles that can prevent urine from leaking out.
The first one is the internal sphincter muscle, which is made of smooth muscle and is under involuntary control and typically opens up when the bladder is about half full.
The second one is the external sphincter muscle, and it’s made of skeletal muscle and is under voluntary control. This is the reason that it’s possible to stop urine mid-stream by tightening up that muscle.
Once urine has passed through the external sphincter muscle, it can no longer be stopped.Now, when specialized nerves in the bladder wall sense that the bladder is about half full, they send impulses to the spinal cord at levels S2 and S3, also known as the micturition center, and to the pons of the brain.
The spinal cord response is part of the micturition reflex and it causes an increase in parasympathetic stimulation and decrease in sympathetic stimulation which makes the detrusor muscle contract and the internal sphincter relax.
It also decreases motor nerve stimulation to the external sphincter allowing it to relax as well. At this point, urination would occur, if not for the pons.
The pons is the region that we train to voluntarily control urination. If we want to delay urination, the pons overrides the micturition reflex, and when we want to urinate, the pons allows for the micturition reflex to happen.Now, there are several types of urinary incontinence.
The first one is stress incontinence where urine leaks out when there’s a high abdominal pressure. Then there’s urgency incontinence where there’s a sudden urge to urinate.
Then, there’s mixed incontinence which is a combination of stress and urgency incontinence. Finally, there’s overflow incontinence, when the bladder doesn’t empty completely.
Now let’s look at them one by one. Let’s start with stress incontinence which is due to increased abdominal pressure that overwhelms the sphincter muscles and allows urine to leak out.

Stress Incontinence3:13–5:07

Some activities like sneezing, coughing or laughing increase abdominal pressure. This increases the pressure in the bladder and in turn, urine leaks out.
If the pressure in the bladder is greater than the pressure in the sphincters, then the sphincters are unable to hold urine in.
For your tests, remember that if the sphincters are damaged, which is also called an outlet incompetence, then they can’t stop urine from leaking out.
Now, outlet incompetence can be caused by urethral hypermobility or intrinsic sphincter deficiency. Now, urethral hypermobility is a condition where the urethra can’t be kept still by the muscles surrounding it because they are way too weak.
One thing that can weaken the pelvic muscle is vaginal delivery. On the other hand, intrinsic sphincter deficiency is caused by damage to these sphincter muscles, which is often a complication of prostate surgery.
Okay, now, another risk factor for stress incontinence can be obesity because it increases the abdominal pressure and therefore, pressure in the bladder can sometimes be higher than the pressure of the sphincter.
Similarly, pregnancy can also cause stress incontinence since the uterus rests above the bladder. The diagnosis can be made based on a positive bladder stress test where you can directly see urine leaking out when a person is coughing or does the Valsalva maneuver.
This is when the clinician bears down and squeezes the abdominal muscles in order to increase abdominal pressure and cause urine to leak out.
Stress incontinence treatments typically focus on strengthening the pelvic floor muscles by doing Kegel exercises. In individuals with obesity, weight loss is recommended and in females, using pessaries might be helpful.Next there’s urgency incontinence, which is when someone has a sudden urge to urinate because of an "overactive bladder", followed immediately by involuntary urination.

Urgency Incontinence5:07–6:16

This is typically due to an uninhibited detrusor muscle that contracts randomly. This usually results in frequent urination, especially at night.
For your tests, remember that urgency incontinence is usually associated with urinary tract infections. That’s because the inflammation in the bladder might trigger the detrusor muscle, causing it to contract out of nowhere.
For diagnosis, urodynamic studies are generally not needed, but if performed, they will show detrusor overactivity. Now for your exam, it’s important to remember that the first line treatment for urgency incontinence relies on Kegel exercises, bladder training, like establishing a timetable for when to go to the bathroom and empty the bladder, as well as distraction or relaxation techniques.
If behavioral training fails to improve the symptoms, medications such as antimuscarinics like oxybutynin can be used to decrease detrusor muscle contractions.Now stress and urge incontinence are not mutually exclusive, so sometimes you get mixed incontinence, which is basically a combination of both stress and urgency incontinence.

Mixed Incontinence6:16–6:39

This could happen when, say, a pregnant person also develops a urinary tract infection. As a result, urine can leak out with increased abdominal pressure or when there’s random detrusor contractions.Finally, there’s overflow incontinence, which is typically caused by incomplete emptying of the bladder.

Overflow Incontinence6:39–8:07

When the bladder doesn’t empty completely, it fills up and overflows with urine, leading to incontinence. Typically, this results in a weak or intermittent urinary stream or hesitancy where it takes a while for the urine to get flowing because of a blockage in the path.
For your tests, remember that one cause is the blockage in urine flow due to an outlet obstruction, like with benign prostatic hyperplasia in males.
Also remember that another cause is an ineffective detrusor muscle which contracts too little and can’t push out all the urine in the bladder.
Now, an ineffective detrusor muscle can be caused by diabetes, in which case there will also be polyuria, or it can be caused by a neurogenic bladder that’s associated with multiple sclerosis.
In both cases, there’s damage to the nerves that supply the bladder so the signal for the contraction of the detrusor muscle may be weaker.
As far as diagnosis goes, catheterization and ultrasound will show an increased post-void residual volume, which is the volume of urine retained in the bladder after a voluntary void.
Overflow treatments are aimed at re-establishing a clear pathway for urine flow. For example, that might be through catheterization in order to empty the bladder, or medications like alpha-blockers for treating benign prostatic hyperplasia in males.Okay, let’s review!

Review8:07–9:03

Stress incontinence happens when there’s increased abdominal pressure which also increases bladder pressure. If bladder pressure is greater than the urethral pressure, then urine can leak out.
This can happen when the muscles surrounding the urethra are weakened like with vaginal delivery or if there’s trauma to the sphincters like with prostate surgery.
Next there’s urgency incontinence where there’s an urge to urinate due to inappropriate detrusor muscle contractions, and it’s usually associated with urinary tract infections.
Then there’s mixed incontinence which is a combination of stress and urge incontinence. Finally, there’s overflow incontinence where there’s incomplete emptying of the bladder.
This can be due to an outlet obstruction like with benign prostatic hyperplasia or when the detrusor muscle doesn’t contract effectively, like with a neurogenic bladder, for example.Now, back to our cases.

Summary9:03–9:49

First, there’s 70 year old Oleg who often has to go to the bathroom and also has a weak urinary stream. Well, taking into account the fact that Oleg is 70 years old, this could be a case of benign prostatic hyperplasia.
So, in this case, there’s an overflow incontinence caused by the obstruction that’s due to the enlargement of the prostate.
Among other treatments, Oleg might benefit from alpha-blockers. Then there’s Samantha who urinates when she laughs.
If we’d ask Samantha to laugh or cough while we directly examine her, we might see that urine leaks out. Now, considering she also had two vaginal deliveries, this is most likely a case of stress incontinence caused by weakened pelvic muscles and the problem might resolve with