In this retrospective analysis of nine renal transplant recipients with recurrent UTIs who underwent urodynamics, all patients had normal compliance and voiding pressures. Native ureteral reflux occurred in one patient who had a history of a febrile UTI and transplant ureteral reflux in four patients. No patients exhibited an obstructive pattern and management was not altered based on results of urodynamic testing.
The etiology of recurrent UTIs in our cohort is likely multifactorial and patients had several risk factors. Seven patients were female, a finding that mirrors the high female-to-male ratio in other studies and likely reflects the pattern of UTIs in the general population6,7. Five had diabetes mellitus- in a study of nearly 30,000 renal transplant recipients, patients with diabetes had a 43% increased risk of UTI requiring hospitalization7,8. Two had multi-drug resistant uropathogens, which has been found to be an independent predictor for recurrent UTIs2. VUR in a native or transplant kidney was present in five patients, a finding in nearly half of renal transplant recipients with recurrent UTIs in another cohort6. However, the true impact of reflux is unclear as it has also been shown to have no impact on the incidence of UTIs or on graft or patient survival9. While four patients in our cohort had transplant ureteral reflux, the one patient with an abnormal creatinine who experienced recurrent febrile UTIs had native ureteral reflux, and this has been associated with an increased risk of UTI10.
Recipients who experience recurrent UTIs do appear to have worsened renal function. Pelle, et al. found that at one year post-transplantation, mean serum creatinine values were significantly higher in patients who had experienced acute pyelonephritis compared to patients without UTIs (2.01 vs. 1.59, p<0.01). In fact, creatinine clearance was 50% lower in these patients with acute pyelonephritis at four years follow-up compared to those without. In line with this study, our data showed a decline in renal function from a mean serum creatinine nadir after transplant of 0.86 to 1.47 at last follow-up. This decline may be due to VUR causing renal scarring, but the significance of such scarring on long-term graft survival may be minimal as previously discussed6.
The relative lack of literature regarding the role of diagnostic studies in renal transplant recipients with recurrent UTIs leaves providers with minimal guidance for selecting directed and appropriate testing. Among a cohort with recurrent UTIs after transplant, 32 patients underwent renal scintigraphy with 99mTc-dimercaptosuccinic acid (DMSA) and voiding cystourethrogram (VCUG)6. However, focal renal cortical defects detected on DMSA were not associated with inferior graft survival at a median follow-up of 15 years. As these advanced studies did not impact management, DMSA and VCUG may have minimal utility in the diagnostic workup for this population.
Urodynamic studies were performed after renal transplant in our cohort, but Theodorou, et al. subjected 44 patients with known or suspected lower urinary tract dysfunction to pre-transplant urodynamics. 68% of patients had a urodynamic abnormality that precluded renal transplantation, including neuropathic bladder, small capacity bladder, bladder outlet obstruction, or idiopathic detrusor overactivity. 32% of patients underwent surgical treatment prior to transplant11. In contrast to our study, all patients in this cohort had lower tract dysfunction which may have improved the utility of urodynamics. Further studies will need to assess whether these patients had fewer UTIs post-transplant as a result of pre-transplant urodynamics and treatment.
There are several limitations to this study. First, we have a small sample size but this is due to exclusion of patients with neurogenic bladder and lower urinary tract symptoms who had known reasons for developing recurrent UTIs. Second, it is a retrospective study. Furthermore, our mean follow-up time was 2.46 years and bladder dysfunction may become more evident in this population with longer follow-up.