Clinical Pathology · MU Sofia

96. Nephrocirrhosis. Etiology & pathogenesis. Classification. Renal failure.

Explains acute and chronic pyelonephritis, covering bacterial causes such as E. coli, predisposing factors like obstruction and vesicoureteral reflux, and the ascending infection pathway. It describes gross and microscopic changes in each form, includes a biopsy micrograph of acute disease, and contrasts chronic pyelonephritis scarring with vascular nephrosclerosis. Clinical features and summary questions close the note.

Inside: 4 sections · 1 labelled picture · 14 flashcards · 3 min

Topic 96 of 138 in the MU Sofia syllabus for Clinical Pathology (Medicine, Year 4). The free AceMed note covers it in 4 sections, about 452 words (3 min of reading), with 14 flashcards.

In this note

  1. Nephrocirrhosis. Etiology & pathogenesis. Classification. Renal failure
  2. Acute Pyelonephritis (PN)
  3. Chronic Pyelonephritis (PN)
  4. Summary Questions

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:

  1. 1. Gross:
  • Swollen kidneys, abscesses, or pus-filled foci in the renal cortex.
  • Abscess formation may lead to pyonephrosis if untreated.
  1. 2. 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).

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