Abnormal tubulointerstitial morphology Tubulointerstitial fibrosis HP:0004714 HP:0000129 A progressive detrimental connective tissue deposition (fibrosis) on the kidney parenchyma involving the tubules and interstitial tissue of the kidney. Tubulointerstitial injury in the kidney is complex, involving a number of independent and overlapping cellular and molecular pathways, with renal interstitial fibrosis and tubular atrophy (IF/TA) as the final common pathway. However, IF and TA are separable, as shown by the profound TA in renal artery stenosis, which characteristically has little or no fibrosis (or inflammation). For new annotations it is preferable to annotate to the specific HPO terms for Renal interstitial fibrosis and/or Renal tubular atrophy. UMLS:C1969372 HP:0008171 This finding is usually shown by renal biopsy. Fibrosis involves an excess accumulation of extracellular matrix and usually results in loss of function when normal tissue is replaced with scar tissue. Tubulointerstitial renal fibrosis, characterized as a progressive detrimental connective tissue deposition on the kidney parenchyma, appears to be a harmful process leading inevitably to renal function deterioration, independently of the primary renal disease which causes the original kidney injury. Epithelial to Mesenchymal Transition (EMT) of tubular epithelial cells which are transformed to mesenchymal fibroblasts migrating to adjacent interstitial parenchyma constitutes the principal mechanism of renal fibrosis along with local and circulating cells. (PMID:20011086) Tubulointerstitial scarring Tubulointerstitial renal fibrosis HP:0005576 Renal fibrosis