Acute pyelonephritis

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Acute pyelonephritis

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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 suprapubic 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?  

External References

First Aid

2024

2023

2022

2021

Acute pyelonephritis p. 619

labs/findings p. 729

renal papillary necrosis and p. 619

WBC casts in p. 612

Chronic pyelonephritis p. 619

labs/findings p. 729

Diabetes mellitus p. 350-358

pyelonephritis and p. 619

Pregnancy p. 651

pyelonephritis p. 619

Proteus spp.

xanthogranulomatous pyelonephritis p. 619

Pyelonephritis p. 619

kidney stones p. 622

labs/findings p. 729

urinary tract infections p. 179

WBC casts in p. 612

Renal papillary necrosis p. 619

pyelonephritis and p. 619

Urinary tract infections (UTIs) p. 179, 619

pyelonephritis p. 619

Urosepsis p. 619

Vesicoureteral reflux p. 597

pyelonephritis p. 619

Xanthogranulomatous pyelonephritis p. 619

Transcript

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With acute pyelonephritis, pyelo- means pelvis, and -neph- refers to the kidney, so in this case it’s the renal pelvis, which is the funnel-like structure of the kidney that drains urine into the ureter, and -itis means inflammation. So acute pyelonephritis describes an inflamed kidney that develops relatively quickly, usually as a result of a bacterial infection.

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 the ureters, and the lower portion of the tract—the bladder and urethra. So acute pyelonephritis is a type of upper urinary tract infection.

Acute pyelonephritis is most often caused by ascending infection, meaning bacteria start by colonizing the urethra and bladder, which would be a lower urinary tract infections, and make their way up the ureters and kidney, therefore upper UTI shares a lot of the same risk factors as lower UTI, things like female sex, sexual intercourse, indwelling catheters, diabetes mellitus, and urinary tract obstruction.

One major factor that increases the risk of an upper UTI from a lower UTI spreading upward is vesicoureteral reflux, or VUR, which is where urine is allowed to move backward up the urinary tract, which can happen if the vesicoureteral orifice fails. The vesicoureteral orifice is the one-way valve that allows urine to flow from each ureter into the bladder, but not in the reverse direction.

VUR can be the result of a primary congenital defect or it can be caused by bladder outlet obstruction, which increases pressure in the bladder and distorts the valve.

As kind of a double-whammy, obstruction also leads to urinary stasis, where urine stands still, which makes it easier for bacteria to adhere and colonize the urinary tract.

So, for ascending infections that cause acute pyelonephritis, the most common organisms are E coli, Proteus species, and Enterobacter species, all of which are commonly found in the bowel flora.

Summary

Acute pyelonephritis is a sudden, severe infection of the kidney. The infection may be caused by bacteria that travel up from the bladder or bacteria circulating in the blood (bacteremia). Symptoms of acute pyelonephritis can include fever, chills, nausea, vomiting, and pain in the lower back and sides. If left untreated, acute pyelonephritis can lead to serious complications like sepsis (a potentially life-threatening condition caused by infection).

Sources

  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  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)
  5. "International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women: A 2010 Update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases" Clinical Infectious Diseases (2011)
  6. "Renal ultrasound and DMSA screening for high-grade vesicoureteral reflux" Pediatrics International (2016)
  7. "EAU Guidelines on Vesicoureteral Reflux in Children" European Urology (2012)
  8. "International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women: A 2010 Update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases" Clinical Infectious Diseases (2011)
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