Proximal Tubular Injury in Medullary Rays Is an Early Sign of Acute Tacrolimus Nephrotoxicity

Figure 2

Diagrammatic changes in pars recta (PR) in normal kidney (left panel), in kidney with acute tacrolimus (FK) nephrotoxicity (middle panel) and in kidney with chronic tacrolimus nephrotoxicity (right panel). In this simplified kidney diagram of normal kidney (left panel), the pars convoluta (PC) located in labyrinth of cortex is connected with pars recta (PR) in medullary rays and outer stripe of outer medulla. The latter is further connected with distal nephron tubules including loop of Henle (LH), distal tubules (DT), and collecting duct (CD). The arcuate artery (AA) is located at the cortical-medullary junction. During acute tacrolimus nephrotoxicity (middle panel), PR becomes dilated (dashed segment) that injury can be detected by positive KIM-1 staining. During chronic tacrolimus nephrotoxicity (right panel), the PR becomes atrophic with surrounding striped fibrosis (illustrated with solid bar) along the medullary rays.