Aspirin and Kidney Disease a Love Hate relationship.

Image by Benjah-bmm27

Acetylsalicylic acid otherwise known as aspirin was a major advance in the treatment of inflammation when it was first discovered in 1853. The chemical compound had been used for centuires before that however in the form of bark and herbs which were found by early man to be helpful for the relief of pain.

The chemical structure above served for the development of many novel drugs with potent anti inflammatory effects and became one of the most prescribed classes of medication in history collectively known as the non steroidal antiinflammatory drugs or NSAIDs. The sideffects of the Aspirin are shown below in this mindmap by maderoh88

NEGATIVE EFFECTS ON THE KIDNEY.

Aspirin reduces renal blood flow this is not usually a problem in a healthy person however in a patient who already has decreased blood volume such as patients with dehydration or blood loss this could precipitate acute renal failure. Several types of kidney disease unified by the loss of protein in the urine, may produce a relative low volume state. Despite the obvious retention of fluid in the skin of the feet and around the eyes, the blood vessels are depleted and hence the kidney is also starved for fluid. In such a setting aspirin will further cause reduction of renal blood flow and tip the patient over into acute renal failure.

Aspirin is an anti inflammatory agent yet it has been known to cause inflammation of the tissues of the kidney a state called an allergic interstitial nephritis. Patients with this disorder may have a skin reaction after administration of aspirin followed by high blood pressure abnormal kidney function and decreased urination, thankfully it is usually self limited.

Aspirin has also been associated with an abnormality of the kidney known as membranous nephropathy. This condition results in thickening of the filter of the kidney and loss of protein in the urine.

BENEFICIAL USES.

Aspirins effect on glomerular blood flow can be beneficial. It would be helpful to understand glomerular function to understand why.

Aspirin has the effect of reducing the flow of blood through the kidney in the areas responsible for filtration. While this may not sound like a good thing, this effect is similar to the effect of angiotensin converting inhibitors or ACEI which are prescribed for delaying progression of renal disease. This effect of aspirin is particularly useful in patients with high degrees of protein loss in the urine. Reduction of pressure within the kidney will lead to decreased filtration of protein by the kidney. Hence at one time aspirin was one of the major drugs used in the treatment of membranous nephropathy and other causes of nephrotic syndrome. The drug has fallen out of use for this indication however because of the negative effects on kidney function produced by aspirin. Inflammatory conditions of the kidney were also thought to be treatable by aspirin, conditions such as membranoproliferative glomerulonephritis which is a very rare form of inflammation of the kidney. However all recent trials have discounted any protective effect of aspirin in this and similar conditions.

Although an anti inflammatory agent aspirin has no role in the treatment of inflammatory disorders of the kidney. At this time superior antiinflammatory agents with less negative effects on the kidney are available.