Pathology of the urinary system

3) Renal Cortical Necrosis (often bilateral)

 

   ∙ 

an acute and severe ischemia of the renal cortex due to hypoperfusion, either from thrombosis of 

cortical blood vessels or from shock (which can be of cardiogenic, hypovolemic, septic or 

neurogenic origin); 

   ∙ 

seen with endotoxemia (especially Gram-negative sepsis) and DIC; it can be reproduced (especially 

in rabbits) with two injections of endotoxin 24 hours apart (called Schwartzman reaction); 

   ∙ 

grossly, the affected kidney may have a mosaic appearance (intermixed areas of red and yellow 

discoloration): the reason for this is that, at any given time, not all areas of the renal parenchyma 

work with equal intensity; those areas that are most physiologically active when ischemia hits the 

organ are those likely to sustain the most damage; 

   ∙ 

microscopically, all cortical structures (glomeruli, tubules) are affected; 

   ∙ 

good blood reflow can be expected to follow complete ischemia, provided that the latter lasts less 

than 2 hours; if the animal survives the episode of ischemia, evidence of tubular regeneration may be 

seen within 1 week; 

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   ∙ 

the hemolytic-uremic syndrome (HUS) is a common cause of acute renal failure in humans, 

particularly children, and can have serious long-term sequellae; a major cause of HUS is enteritis 

caused by Shiga toxin-producing strains of 

E. coli

 (particularly 

E. coli

 O157:H7), which are ingested 

in contaminated food such as poorly cooked hamburger; the toxin, absorbed systemically, damages 

endothelial cells of blood vessels, particularly those of the kidneys, thus resulting in thrombotic 

microangiopathy. 

 

Whether medullary or cortical necrosis occurs as a result of ischemia / hypoperfusion depends on its 

severity and duration.  Because of the convoluted tubules’ high metabolic rate, the cortex is more 

susceptible to acute ischemia.  Conversely, the medulla is more susceptible to low-grade, prolonged 

ischemia / hypoperfusion because of its relatively poor vascularity and the low hematocrit and longer travel 

time (low pressure) of blood in its vessels.