Renal toxicity studies are preclinical studies that are conducted to evaluate the potential adverse effects of a substance on the kidneys and urinary system. These studies are typically conducted in laboratory animals, such as rats, mice, or dogs, to assess the safety of a drug or other substance before testing in humans.

The primary objective of renal toxicity studies is to identify any potential adverse effects of the substance on renal function, including changes in kidney weight, histopathological changes in renal tissue, and alterations in serum markers of kidney function, such as creatinine and blood urea nitrogen. These studies can include a range of endpoints, such as urinalysis, histopathological examination of renal tissue, and evaluation of glomerular filtration rate.

Renal toxicity studies can be further classified based on the exposure period and the endpoints evaluated:

1. Acute renal toxicity studies: These studies are conducted to evaluate the potential effects of the substance on the renal system after short-term exposure, usually for a few days to a few weeks.
2. Sub-chronic renal toxicity studies: These studies are conducted to evaluate the potential effects of the substance on the renal system after repeated exposure over a period of several weeks to several months.
3. Chronic renal toxicity studies: These studies are conducted to evaluate the potential effects of the substance on the renal system after repeated exposure over a period of several months to several years.

The results of renal toxicity studies can help identify any potential adverse effects of the substance on the renal system, and can help inform decisions about the safety of the substance for use in humans. These studies are an important part of the preclinical safety assessment of drugs and other substances, particularly those intended for long-term use or for use in populations with a higher risk of renal toxicity.