What does renal interstitial mean?

The kidney interstitial is a normal anatomical structure relative to the kidney parenchyma, mainly the area between the blood vessels and urinary tubules of the kidney. This area contains loose connective tissue and relatively rich interstitial content between cells, mainly some reticular and collagen fibers distributed between the parenchyma, which contain immune cells and fibroblasts. During pathological changes in the kidney, fluid and inflammatory cells seep into the renal interstitium, resulting in fibrosis and chronic inflammation, such as chronic pyelonephritis or interstitial nephritis. The renal interstitium protects the surrounding kidney parenchyma and secretes endocrine hormones, such as prostaglandin and metabolites of cellular components, which can be secreted, transported, stored and metabolized through the renal interstitium.