Reactivation occurs in transplant recipients as a result of immunosuppressive therapy. Serologic evidence suggests that the donor kidney may act as the vehicle of transmission. The typical presentation is a rise in the serum creatinine, which cannot be distinguished from rejection or drug toxicity on clinical grounds. A few cases show hydronephrosis on ultrasound examination at the time of allograft biopsy. Intravenous pyelography in these patients may demonstrate a ureteric stricture.
Hemorrhagic cystitis is described after bone marrow transplantation.
Pathology Findings Needle biopsy of the allograft kidney shows a mixed interstitial inflammatory infiltrate with focal tubular injury. The tubular epithelium shows marked anisonucleosis, nuclear atypia, and basophilic or amphophilic intranuclear inclusions. Tubulitis is frequently present, and satisfies the Banff criteria for acute rejection. In addition biopsies may show clusters of neutrophils in the tubular lumen suggestive of pyelonephritis. Differential diagnosis Acute tubular injury due to ischaemic or immunologic injury can result in a florid regenerative response with extremely prominent nucleoli, which should not be confused with viral inclusions.