Advanced Pathophysiology

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Acute Pyelonephritis

Pyelonephritis is an infection of one or both upper urinary tracts (ureter, renal pelvis, and kidney interstitium). Common causes are summarized in Table 39.4. Urinary obstruction and reflux of urine from the bladder (vesicoureteral reflux) are the most common underlying risk factors. Most cases occur in women.

Acute Pylonephtitis pathophysiology

Pathophysiology.

Microorganisms usually associated with acute pyelonephritis include E. coli, Proteus, and Pseudomonas. The latter two microorganisms are more commonly associated with infections after urethral instrumentation or urinary tract surgery. These microorganisms also split urea into ammonia, making alkaline urine that increases the risk of stone formation. The infection is probably spread by ascending uropathic microorganisms along the ureters. Dissemination also may occur by way of the bloodstream, and both kidneys are usually involved. The inflammatory process is usually focal and irregular, primarily affecting the pelvis, calyces, and medulla. The infection causes medullary infiltration of neutrophils with tubulointerstitial inflammation, renal edema, and purulent urine. In severe infections, localized abscesses may form in the medulla and extend to the cortex. Primarily affected are the renal tubules; the glomeruli usually are spared. Necrosis of renal papillae can develop. After the acute phase, healing occurs with deposition of scar tissue, fibrosis, and atrophy of affected tubules Acute pyelonephritis rarely causes renal failure.68

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