xanthogranulomatous pyelonephritis (XGP)

big kidney
non-functioning (80%)
dilated calyces, thin cortex
calculi (often staghorn)
adult females
usually unilateral
Gram-negative infection, esp. Proteus mirabilis
symptoms: fatigue, low fever, dysuria, flank pain
pathology: granulomata in parenchyma with foam cells, cholesterol slits, fibrosis, atrophic glomeruli
atypical focal form: may resemble focal Ca