Inhibition of cyclooxygenases therefore rather selectively damages the renal papillae, increasing the risk of renal papillary necrosis.NSAIDs caused no adverse effects on renal function in healthy dogs subjected to anesthesia. Most healthy kidneys contain enough physiologic reserve to compensate for this NSAID-induced decrease in blood flow. However, those subjected to additional injury from phenacetin or paracetamol may progress to analgesic nephropathy. Phenacetin and paracetamol
It is unclear how phenacetin induces injury to the kidney. Bach and Hardy have proposed that phenacetins metabolites lead to lipid peroxidation that damages cells of the kidney.Paracetamol is the major metabolite of phenacetin and may contribute to kidney injury through a specific mechanism. In cells of the kidney, cyclooxygenases catalyse the conversion of paracetamol into N-acetyl-p-benzoquinoneimine (NAPQI). NAPQI depletes glutathione via non-enzymatic conjugation with glutathione, a naturally occurring antioxidant. With depletion of glutathione, cells of the kidney become particularly sensitive to oxidative damage. Diagnosis
Diagnosis is traditionally based on the clinical findings above in combination with excessive analgesic use. It is estimated that between 2 and 3 kg each of phenacetin or aspirin must be consumed before evidence of analgesic nephropathy becomes clinically apparent.Once suspected, analgesic nephropathy can be confirmed with relative accuracy using computed tomography (CT) imaging without contrast. One trial demonstrated that the appearance of papillary calcifications on CT imaging was 92% sensitive and 100% specific for the diagnosis of analgesic nephropathy. Treatment
Treatment of analgesic nephropathy begins with the discontinuation of analgesics, which often halts the progression of the disease and may even result in normalization of kidney function.
An autopsy study performed in Switzerland suggested that the prevalence of analgesic nephropathy in the general population has likewise decreased; the prevalence was 3% in 1980 and 0.2% in 2000.While these data demonstrate that analgesic nephropathy has been all but eliminated in some regions, in other regions the condition persists. Notably, in Belgium, the prevalence of analgesic nephropathy among people having dialysis was 17.9% in 1984 and 15.6% in 1990. Michielsen and de Schepper suggest that analgesic nephropathy persists among people in Belgium having dialysis not due to non-phenacetin analgesics, but because Belgium accepts a higher proportion of elderly people for dialysis. According to these authors, a greater proportion have analgesic nephropathy because a greater percentage of people in Belgium having dialysis have been exposed to long-term use of phenacetin. Terminology
The term analgesic nephropathy usually refers to damage induced by excessive use of combinations of these medications, specifically combinations that include phenacetin. For this reason, it is also called analgesic abuse nephropathy. Murray prefers the less judgmental analgesic-associated nephropathy. Both terms are abbreviated to the acronym AAN, by which the condition is also commonly known. References


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