Systematic kidney biopsies after acute allograft pyelonephritis.

Objectives: Scarce data exist regarding the effect of acute graft pyelonephritis on kidney histology after a kidney transplant. This study sought to assess the kidney histology at 1 month, and kidney function at 1 year, after acute graft pyelonephritis in kidney transplant patients.
Materials and Methods: All kidney transplant patients with acute graft pyelonephritis between October 2006, and December 2008, underwent a kidney biopsy 1 month later (n=28). Histologic findings were compared with those observed in a control group (n=28) who underwent a protocol kidney biopsy at 1 year posttransplant and did not present with acute graft pyelonephritis. Patients were matched according to age, sex, and immunosuppressive regimen.
Results: Kidney function was impaired by the acute graft pyelonephritis episodes at the time of biopsy. In 40% of patients, the estimated glomerular filtration rate did not return to baseline by 1 month after acute graft pyelonephritis and remained impaired thereafter. Three patients had features of acute rejection. Tubulitis was seen more frequently in the acute graft pyelonephritis group, especially in patients in whom estimated glomerular filtration rate did not completely recover by 1 month after acute graft pyelonephritis. Patients with acute graft pyelonephritis who had inflammatory infiltrate of > 20% 1 month after acute graft pyelonephritis had worse kidney function 1 year later.
Conclusions: After transplant, when kidney function remains impaired 1 month after acute graft pyelonephritis, kidney biopsies allowed graft rejection diagnosis and predicted kidney function recovery.