What is the etiology and pathophysiology of pyelonephritis?

Updated: Aug 27, 2019
  • Author: John L Brusch, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

Pyelonephritis is an infection of the renal parenchyma. Infection usually occurs in a retrograde, ascending fashion from the bladder, but it may occur hematogenously. The ureteral orifice becomes edematous and loses its one-way valve function during infection. Retrograde flow of bacteria into the upper urinary tracts and into the renal parenchyma results in clinical symptoms.

Bacteremia, particularly with virulent organisms such as S aureus, can result in pyelonephritis with focal renal abscesses. Bacterial adherence allows for mucosal colonization and subsequent infection by an ascending route. Whereas type 1 pili are produced by most uropathogenic strains of E coli, P-pili, which bind to the uroepithelial glycosaminoglycan layer, are found in most strains of E coli that cause pyelonephritis. Genotypic factors may affect uroepithelial susceptibility to these adherence molecules. Endotoxin from gram-negative organisms can retard ureteral peristalsis.

E coli is responsible for approximately 25% of cases in males, with Proteus and Providencia causing many remaining infections; Klebsiella, Pseudomonas, Serratia, and enterococci are less frequent.


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