Nephrocirrhosis. Etiology & pathogenesis. Classification. Renal failure
Pyelonephritis (PN) refers to inflammation of the kidney parenchyma (renal interstitium and tubules), commonly caused by bacterial infections. It can be acute (sudden onset) or chronic (progressive, long-term inflammation). These conditions primarily affect the tubulointerstitial area of the kidney, leading to potential renal dysfunction.
Acute Pyelonephritis (PN)
Etiology:
- Bacterial infection, primarily due to Escherichia coli (E. coli), but also Klebsiella, Proteus, Enterococcus, and Pseudomonas.
- Predisposing factors:
- Urinary tract obstruction (e.g., kidney stones, enlarged prostate).
- Vesicoureteral reflux (VUR), which allows retrograde urine flow.
- Diabetes, pregnancy, immunosuppression.
Pathogenesis:
- Ascending infection from the lower urinary tract to the kidneys.
- Bacterial adhesion to urothelium followed by invasion and inflammatory response in the renal interstitium and tubules.
- Inflammatory mediators (e.g., cytokines, chemokines) attract neutrophils and cause tissue damage.
Microscopic & Gross Pathology:
- Gross:
- Swollen kidneys, abscesses, or pus-filled foci in the renal cortex.
- Abscess formation may lead to pyonephrosis if untreated.
- Microscopic:
- Neutrophilic infiltration of the renal interstitium and tubules.
- Patchy necrosis of renal tubules.
- Tubular cell damage and possible abscesses in severe cases.
- Glomeruli are typically unaffected.
H&E, kidney biopsy: acute pyelonephritis – the interstitium between the tubules is packed with inflammatory cells, many of them neutrophils, while the two glomeruli (centre) are spared.
Image: “Acute pyelonephritis - high mag” by Nephron, CC BY-SA 3.0, via Wikimedia Commons.
Clinical Features:
- Flank pain, fever, dysuria, urgency.
- Positive urine culture with the causative organism.
- Costovertebral angle tenderness (CVA tenderness).