#2980 The natural history of urinary tract infections in kidney transplant recipients
Authors: Elhoweris Ala Eldin , Sullivan Micheal , Norton William , Salim Ehsan , Aitken Emma 
Published: May 2024

Abstract

Background and Aims
Urinary tract infections (UTIs) can occur following kidney transplantation, but research on infection rates and outcomes is inconclusive. We therefore aimed to provide a comprehensive understanding of the natural history of UTIs and the impact on long-term outcomes.

Method
We performed a single-centre cohort study of kidney-only transplant recipients at the Glasgow Transplant Unit, UK. A standardised protocol for UTI screening and treatment was in use and only treated UTIs were included. We studied the first two years post-transplant as this is the time when UTIs are most likely to occur. Patients were categorised into 3 groups based on number of UTIs: no UTIs, 1-2 UTIs and ≥3 UTIs. Furthermore, patients with highly recurrent UTIs defined as ≥10 UTIs in the first 2 years were compiled and analysed. Proportional odds logistic regression was performed to identify risk factors for having ≥3 UTIs, with adjustment for age, sex, primary renal diagnosis, donor type (live donor, deceased heart beating, deceased non-heart beating) and induction immunosuppression.

Results
Amongst 1412 transplant recipients studied over a nine-year period, the mean age was 48 years and 563 (39.9%) were female. 1169 (82.8%) of recipients experienced no UTIs, 180 (12.7%) had 1-2 UTIs, and 63 (4.5%) had ≥3 UTIs (Fig. 1). The key risk factors for developing ≥3 UTIs were female sex: adjusted odds ratio (aOR) 1.50 (95% confidence interval 1.13-1.99), induction with anti-thymocyte globulin (ATG): aOR 6.60 (3.05-14.05), and age: aOR for each one-year increase 1.01 (1.00-1.02). There were no primary renal diagnoses (PRD) that demonstrated a significant association with ≥3 UTIs. However, individuals with tubulointerstitial disease, a group which includes structural abnormalities of the urinary tract and reflux nephropathy as a considerable proportion, showed a trend towards heightened risk: aOR 1.47 (0.97-2.22, reference group glomerulonephritis). Recipients with ≥3 UTIs had lower estimated glomerular filtration rates (eGFRs) at two years compared to the no UTI group (49.7 vs. 59.2mL/min/1.73 m2, respectively). However, there was no significant increase in mortality or graft loss between the three groups. In the group of patients with highly recurrent UTIs, consisting of 14 patients (0.01%), we observed that 3 (21%) had a PRD of reflux nephropathy, while 5 (35%) had underlying structural abnormalities of the native renal tract as a PRD. Further to this 5 (35%) of the patients received ATG induction and 5 (35%) patients had a previous transplant.

Conclusion
We describe a low rate of UTIs requiring treatment in the first two years after kidney transplantation. Females, older recipients and those given ATG induction were at increased risk of recurrent UTIs. There was no impact of UTIs on graft loss or patient mortality. However, eGFR at two years post-transplant was lower amongst those with recurrent UTIs. We also observed that for the patients with highly recurrent UTIs, ATG induction, previous transplants, reflux nephropathy and structural abnormalities of native renal tract may be a risk factor. Recipients at highest risk of UTIs should therefore be screened for UTIs and interventions to reduce this risk should be considered