Chronic pyelonephritis and reflux nephropathy
- Lesion
Repeated infection with reflux or obstruction scars the kidney unevenly and deforms the calyces under the scars.
What it is
Chronic pyelonephritis is tubulointerstitial inflammation and scarring with deformity of the pelvicalyceal system. Two settings produce it: reflux nephropathy, from childhood vesicoureteral reflux with infection, and chronic obstruction, which favours repeated infections. Its distinctive feature, compared with other chronic tubulointerstitial disease, is the coarse scar over a blunted, dilated calyx. Xanthogranulomatous pyelonephritis is an uncommon destructive variant with foamy macrophages, often with Proteus and staghorn stones.
Structure
- One or both kidneys small and irregularly scarred; in contrast to vascular disease, the scars are coarse and few.
- Calyces under the scars are blunted, flattened or dilated.
- Tubules are either atrophic or dilated with pink casts resembling thyroid follicles.
- Lymphocytes, plasma cells and sometimes neutrophils in a fibrotic interstitium; arterioles thicken with hypertension.
Paths to chronic pyelonephritis
| Setting | Mechanism | Typical findings |
|---|---|---|
| Reflux nephropathy | Infected urine refluxes into the kidney from childhood | Polar scars, often bilateral; hypertension and proteinuria later |
| Chronic obstruction | Stasis favours recurrent infection; pressure adds atrophy | Diffuse or one-sided scarring with hydronephrosis |
| Xanthogranulomatous pyelonephritis | Chronic obstruction, often with staghorn stone and Proteus | Yellow destructive mass of foamy macrophages |
Clinical notes
- Insidious onset of kidney insufficiency and hypertension, or found when imaging shows scars.
- Proteinuria and secondary FSGS signal a poor outcome.
- Early screening and treatment of reflux in children with urinary infection aims to prevent scarring.
Test yourself
Think of the answer, then tap the question to see it.
Which feature separates chronic pyelonephritis from other chronic tubulointerstitial diseases?
Coarse cortical scars overlying blunted or deformed calyces.
What is thyroidization of the kidney?
Atrophic tubules filled with eosinophilic hyaline casts that resemble thyroid follicles.
Why do reflux scars favour the poles of the kidney?
Polar papillae are often compound, with openings that let urine reflux into the parenchyma.
Elsewhere in DurgiPedia
- Chronic inflammation: causes, cells and features
- Fibrosis in organs: TGF-β and the myofibroblast
- Duplicated ureter, UPJ obstruction and posterior urethral valves
Connections
Microorganisms1
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Acute Pyelonephritis (StatPearls (NCBI Bookshelf), 2024).
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Representative model, for educational purposes only.