Persisting Aseptic pyelonephritis following acute bacterial
Acute pyelonephritis (APN) is a common cause of AKI in kidney graft recipients but only few cases of severe AKI following uncomplicated non obstructive native kidney APN have been reported. Fifteen patients were studied following the case definition, defined as the presence of one of the following criteria: arterial blood pressure <65 mmHg, lactataemia 2 mmol/L, fluid resuscitation needs 3000 ml in the first 24 hours of sepsis, multisystemic dysfunction. Acute kidney injury according to the Kidney Disease: Improving Global Outcome classification wild type Retinol-binding protein, normal value <0.08 mg/mmol of creatinine last follow-up.

Eight patients were treated with corticosteroids (0.5 or 1mg/kg tapered over a mean duration of 1.2 +/- 1.0 month) and antibiotics (mean duration 5.4 +/- 2.7w), four with antibiotics only, and three with corticosteroids only. There were no reported side effects of corticosteroids.

After a mean follow up of 8.7±3.8 months, kidney function stabilized or improved in all patients (mean eGFR variation to biopsy +18.7±21.6 ml/min/1.73m2, p=0.02). However, renal function often remained severely hampered (mean eGFR 38.3±27.5 ml/min/1.73m2, mean eGFR loss to baseline -27.3±10.8 ml/min/1.73m2). By the end of the study follow up 9/15 patients (60%) presented stage IV or V CKD versus none before APN onset.

Urinary signs of active TIN regressed in all treated patients (leukocyturia at last follow up (LFU) 5000 IQR[5000-113250] elts/mm3, median variation of -35000 IQR [0-156000]). Two patients died respectively after 2 and 12 months of follow-up. The second patient beneficiated steroid therapy from the third to the fifth month of follow-up.

Better renal outcome (i.e. last follow up – LFU – eGFR>30mL/min) was associated with early steroid treatment initiation (< 65 days) and higher baseline and per-AKI eGFR in an univariate analysis (Supplementary Table S1). The presence of lymphoid nodules tended to be associated with a worse outcome.

They further compared the patients’ renal function according to corticosteroid exposure (Supplementary Figure S1). Baseline, APN and kidney biopsy eGFR were not significantly different but LFU eGFR was significantly higher in the CTC group 45.8±28.1 versus 17.5±10.1 ml/min/1.73m2, p=0.01.