APhenylbutazone works by inhibiting the formation of prostaglandins, the chemical byproducts of inflammation. Prostaglandins appear to have an influence on perfusion (blood flow) into the tissues of the kidney. In certain circumstances, especially when the animal is dehydrated, phenylbutazone might induce a serious disorder called papillary necrosis by inhibiting the formation of prostaglandins. To prevent this problem, caution should be taken not to administer the drug to horses with serious dehydration due to diarrhea, overexertion, or other water depletion situations. If the need is great to reduce inflammation, the treatment should be accompanied by fluid therapy.

There should be no difference between geldings and intact males or females in regard to this problem. Sometimes geldings exhibit discomfort or an unusual posture when urinating, which is almost always due to the buildup of smegma in the opening of the urethra. This buildup is usually referred to as a "bean," which can be remedied by cleaning the penis and urethra carefully.

Often symptoms of tenderness or pain over the back are interpreted as kidney problems. This is almost never the case. When a horse has kidney disease, it has much bigger problems than a sore back