 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 papillary necrosis cause diminished flow through these arteries, either through direct mechanical obstruction (sickle cell), obstruction secondary to inflammation (vasculitides), or vasoconstriction (NSAIDs).Papillary necrosis is more likely to develop when multiple of these underlying factors are present.