label: Renal interstitial fibrosis
label_lc: renal interstitial fibrosis
description: "The accumulation of collagen and related extracellular matrix (ECM) molecules in the interstitium of the kidney. The interstitium is expanded by the presence of collagen that stain blue on trichrome. Tubules are not back to back, but rather separated by fibrosis and can be atrophic."