Urinary incontinence
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Urinary incontinence
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USMLE® Step 1 style questions USMLE
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| Laboratory value | Result |
| Glucose | 167 mg/dL |
| HbA1c | 8.1% |
| Postvoid residual volume | 170 ml |
Which of the following best describes the pathophysiology of this patient’s symptoms?
Memory Anchors and Partner Content
External References
First Aid
2024
2023
2022
2021
Antimuscarinic drugs
urgency incontinence p. 618
Benign prostatic hyperplasia (BPH) p. 672, 734
incontinence with p. 618
Diabetes mellitus p. 350-358
urinary incontinence with p. 618
Incontinence (fecal/urinary) p. 464
Mixed incontinence (urinary) p. 618
Urinary incontinence p. 618
drug therapy for p. 240
ephedrine for p. 241
hydrocephalus p. 536
multiple sclerosis p. 537
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Urinary incontinence is a problem where the process of urination, also called micturition, happens involuntarily, meaning that a person might urinate without intending to.
Urinary incontinence 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.
Normally, urine is held in the bladder, which receives urine from two ureters coming down from the kidneys and then that urine leaves the bladder through the urethra. As urine flows from the kidney, through the ureters and into the bladder, the bladder starts to expand into the abdomen.
The bladder is able to expand and contract because it’s wrapped in a muscular layer, called the detrusor muscle, and within that, lining the bladder itself is a layer of transitional epithelium containing “umbrella cells”. These umbrella cells get their name because they physically stretch out as the bladder fills, just like an umbrella opening up in slow-motion. In a grown adult, the bladder can expand to hold about 750ml, slightly less in women than men because the uterus takes up space which crowds out the bladder a little bit.
Alright, so when the urine is collecting in the bladder, there are basically two “doors” that are shut, holding that urine in. The first door is the internal sphincter muscle, which is made of smooth muscle and is under involuntary control, meaning that it opens and closes automatically. Typically, that internal sphincter muscle opens up when the bladder is about half full.
The second door is the external sphincter muscle, and it’s made of skeletal muscle and is under voluntary control, meaning that it opens and closes when a person wants it to. This is the reason that it’s possible to stop urine mid-stream by tightening up that muscle, which is called doing kegel exercises.
Once urine has passed through the external sphincter muscle, it exits the body—in women the exit is immediate and in men the urine flows through the penis before it exits.
So when specialized nerves called stretch receptors in the bladder wall sense that the bladder is about half full, they send impulses to the spinal cord, specifically the sacral spinal cord at levels S2 and S3, known as the micturition center, and the brain, specifically two locations in the pons—the pontine storage center and pontine micturition center.
Summary
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.
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