What is the role of obstruction in the pathogenesis of acute pyelonephritis (kidney infection)?

Updated: Jul 01, 2021
  • Author: Tibor Fulop, MD, PhD, FACP, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Obstruction is the most important factor. It negates the flushing effect of urine flow; allows urine to pool (urinary stasis), providing bacteria a medium in which to multiply; and changes intrarenal blood flow, affecting neutrophil delivery. Obstruction may be extrinsic or intrinsic. Extrinsic obstruction occurs with chronic constipation (particularly in children), prostatic swelling/mass (eg, hypertrophy, infection, cancer), and retroperitoneal mass.

Intrinsic obstruction occurs with bladder outlet obstruction, cystocele, fungus ball, papillary necrosis, stricture, and urinary stones. With increasing size of stone, the probability of stone passage decreases while the probability of obstruction increases. Nonetheless, stones as small as 2 mm have resulted in obstruction, while 8-mm stones have occasionally passed spontaneously.

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