This condition is due to ischemia of the renal papillae, the portion of the kidney that collects urine from the nephron. The papillae are vulnerable to ischemia as they are supplied by small caliber arteries which are liable to obstruction. All of the underlying causes of<unk>  necrosis cause diminished flow through these arteries, either through direct mechanical obstruction (sickle cell), obstruction secondary to inflammation (vasculitides), or vasoconstriction (NSAIDs).<unk>  necrosis is more likely to develop when multiple of these underlying factors are present. Ultimately, necrosis of the papillae results in sloughing into the lumen, causing hematuria. If the degree of necrosis is substantial post-renal failure may occur, though this is uncommon.
Renal papillary necrosis
Renal cortical necrosis
Acute tubular necrosis
Shunt nephritis
Contrast-induced nephropathy
Glomerulonephrosis
Interstitial nephritis
Acute uric acid nephropathy