How is ATN differentiated from rejection in renal transplant patients?
Clinically, ATN occurs almost immediately after transplantation whereas chronic rejection generally occurs over several days to several weeks or longer after transplantation. ATN can occur later, although it is usually associated with some specific event that damages the transplant and usually takes several weeks or months to resolve after transplantation. Renal scan findings are often different for ATN and rejection. ATN shows normal or only slightly diminished perfusion of the kidney with a delayed cortical transit time, whereas rejection is usually associated with diminished flow with mildly impaired cortical function. In severe rejection, flow and function are both markedly reduced. In both cases, when minimal or no urine is produced, it is impossible to exclude a leak or urinary tract obstruction as the underlying etiology, because both of these entities require some radioactive urine to be excreted into the urothelial system. It is also possible to have superimposed ATN and rejection, particularly when a renal scan reveals diminished flow and function. A clinician may have to treat such patients for both conditions