AKI Due to Asymptomatic Pyelonephritis in a Kidney Transplant Recipient

Introduction: Kidney transplant recipients with a positive urine culture but no symptoms of urinary tract infection (UTI) are typically diagnosed with asymptomatic bacteriuria and usually do not receive antibiotic treatment. However, in this report, we describe a case of acute kidney injury (AKI) due to asymptomatic pyelonephritis, which responded to antibiotic therapy. Case Description: A 62-year-old woman with a history of end-stage kidney disease due to hypertension underwent a deceased donor kidney transplant. Her post-transplant course was complicated by delayed graft function and early borderline acute cellular rejection, which was treated with high-dose oral prednisone. One month post-transplant, she had removal of ureteropelvic stent. Two months post-transplant, she developed a symptomatic urinary tract infection (UTI) caused by multidrug-resistant Klebsiella pneumoniae, accompanied by acute kidney injury (AKI), and was treated with intravenous antibiotics. Three months post-transplant, she presented again with AKI. Although her urine culture was positive for the same organism, she did not exhibit any UTI symptoms and was initially not given antibiotics. A kidney biopsy performed for evaluation of AKI revealed severe tubulointerstitial inflammation with neutrophil casts, indicative of acute pyelonephritis. Consequently, she was treated with intravenous antibiotics, resulting in an improvement in her serum creatinine levels. Discussion: Monitoring for and treating asymptomatic bacteriuria is typically not recommended beyond two months post-kidney transplant due to a lack of evidence for improved outcomes and concerns about antibiotic resistance. However, our case demonstrates that biopsy-proven acute pyelonephritis, severe enough to cause AKI, can be asymptomatic in kidney transplant recipients. Therefore, acute pyelonephritis should be considered as a potential cause of AKI in patients with asymptomatic bacteriuria when no other clear etiology for AKI is present.