Pathology of the urinary system

4) Renal Medullary (Papillary) Necrosis

 

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renal medullary necrosis may result from treatment with anti-inflammatory and analgesic drugs such 

as phenylbutazone, phenacetin, aspirin (analgesic nephropathy in humans):  these drugs inhibit the 

synthesis of prostaglandin (PGE

2

) in the renal medulla, and prostaglandin is required to maintain 

blood perfusion in the highly hypertonic environment of the papillary interstitium; dehydration (e.g. 

from inadvertent water deprivation) is an important compounding factor; experimentally, renal 

medullary necrosis could be reproduced in horses treated with phenylbytazone for 1-10 weeks and 

deprived of water for 36-48 hours prior to euthanasia; 

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can be secondary to other renal lesions, e.g. medullary amyloidosis in cats, pyelitis, pelvic calculi, 

etc.; these lesions can easily occlude by compression the long thin-walled blood vessels supplying 

the medulla; 

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grossly: 

the renal papilla appears necrotic and is often demarcated by a zone of hyperemia and 

hemorrhage; 

    

 

 

in more advanced cases, the necrotic papilla detaches from the kidney, causing severe 

scarring.