Lower urinary tract infection

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Lower urinary tract infection

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Lower urinary tract infection


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Lower urinary tract infection

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USMLE® Step 1 style questions USMLE

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A 67-year-old woman is currently postoperative day 5 after having an open cholecystectomy. She reports worsening subprapubic pain and malaise.  Her vital signs are 37 °C (98.6°F), pulse is 98/min, respirations are 14/min, blood pressure is 137/64 mmHg, and oxygen saturation is 99% on room air. Physical examination shows suprapubic tenderness on palpation as well as cloudy urine in her Foley catheter. Which of the following pathogens is most likely causative of this patient’s clinical presentation?  

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Acute cystitis p. 618


acute bacterial p. 618, 625

squamous cell carcinoma risk p. 624

Dysuria p. 678

cystitis p. 179


Content Reviewers

With cystitis, cyst- refers to the bladder, and -itis refers to inflammation, therefore cystitis describes an inflamed bladder, which is usually the result of a bacterial infection, but also can result from fungal infections, chemical irritants, foreign bodies like kidney stones, as well as trauma.

Now a urinary tract infection, or UTI, is any infection of the urinary tract, which includes the upper portion of the tract—the kidneys and ureters, and the lower portion of the tract—the bladder and urethra.

So cystitis, when it’s caused by an infection, is a type of lower UTI.

Lower UTIs are almost always caused by an ascending infection, where bacteria typically moves from the rectal area to the urethra and then migrate up the urethra and into the bladder.

Having said that, on rare occasions, a descending infection can happen as well where bacteria starts in the blood or lymph and then goes to the kidney and makes its way down to the bladder and urethra.

Normally, urine is sterile, meaning bacteria doesn’t live there; the composition of urine, which has a high urea concentration and low pH, helps keep bacteria from setting up camp.

Also, though, the unidirectional flow in the act of urinating also helps to keep bacteria from invading the urethra and bladder.

Some bacteria, though, are better surviving in and resisting these conditions, and can stick to and colonize the bladder mucosa.


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  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
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  6. "Diagnosis and management of urinary infections in older people" Clinical Medicine (2011)
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