Serum Uric Acid Levels and Kidney Transplant Outcomes: Cause, Consequence, or Confounded?

Prevalence and potential relevance of hyperuricemia in pediatric kidney transplant recipients-a CERTAIN registry analysis

BACKGROUND

Asymptomatic hyperuricemia is frequently observed in pediatric kidney transplant recipients; symptomatic hyperuricemia, however, is a rare complication. Only few data are available in this patient population. We, therefore, investigated the prevalence of hyperuricemia and its association with kidney transplant function and blood pressure in a multicenter cohort of pediatric kidney transplant recipients.

METHODS

This is a retrospective, observational multicenter registry study. All pediatric kidney transplant recipients in the CERTAIN database with at least one documented serum uric acid level and a follow-up of 5 years posttransplant were eligible. We identified 151 patients with 395 measurements of serum uric acid. We calculated the prevalence of hyperuricemia, analyzed potential risk factors and clinical consequences such as elevated blood pressure and reduced estimated glomerular filtration rate (eGFR). Statistical analysis was performed using IBM SPSS Statistics 26.

RESULTS

One hundred and ten of 395 (27.8%) serum uric acid levels were above 416 µmol/L (7.0 mg/dL), defined as the upper limit of normal. Univariate analysis showed a significant (p = .026) inverse association of serum uric acid with eGFR overtime. There was no significant association of serum uric acid concentrations with body mass index (z-score), blood pressure (z-score), or sex. No episodes of gout were documented.

CONCLUSION

This study shows that hyperuricemia is present in a considerable number of patients sometime after pediatric kidney transplantation and is associated with lower eGFR. Whether hyperuricemia contributes to faster decline of graft function or to the overall cardiovascular risk of these patients remains to be elucidated.

Sex differences in uric acid levels in kidney transplant recipients and their donors: a preliminary retrospective cross-sectional study

Background

Higher serum uric acid (UA) levels are associated with poorer renal prognosis. In kidney transplantation, both donors and recipients are diagnosed as having chronic kidney diseases (CKD) based on renal function; however, their UA levels slightly vary. Elucidating the differences in UA would help improve kidney prognosis, especially for recipients. Therefore, we investigated UA levels in kidney transplant recipients by comparing them to those in their donors.

Methods

In this retrospective cross-sectional survey, background information and blood examination results were collected from the donors just before donation and after transplantation in the donors and recipients. Associations between UA and sex estimated glomerular filtration rate (eGFR), and body mass index (BMI) were evaluated. Data were assessed by the Wilcoxon rank-sum test for continuous variables and the chi-squared test for categorical variables; multiple linear regression analyses were performed to determine which factors were associated with renal function before and after transplantation.

Results

Participant characteristics were as follows. The mean donor age (n = 45, 16 men and 29 women) was 55 ± 11 years, and the mean recipient age (n = 45, 25 men and 20 women) was 46 ± 16 years. Sex-related differences (UA levels in men were predominant) existed in the UA of donors before (P < 0.001) and after donation (P < 0.001). Conversely, there were no significant sex-related differences in the UA of recipients (P = 0.51); the mean standardized eGFRs were similar in donors and recipients after transplantation. Multivariate linear regression analysis showed donor UA only correlated with donor sex before donation (P = 0.008). After donation, donor UA was associated with donor sex (P = 0.006), eGFR (P < 0.001), and BMI (P = 0.02). Notably, the UA of recipients after transplantation was only associated with eGFR (P = 0.003).

Conclusions

Sex has less impact on UA in recipients than in donors. UA has a greater impact on renal prognosis in women than men, even at the same UA level. Therefore, attention should be given to UA levels in female recipients. These findings can be useful for determining patient prognosis following kidney transplantation in both donors and recipients.

Post-transplantation diabetes in kidney transplant recipients: an update on management and prevention

Post-transplantation diabetes mellitus (PTDM) may severely impact both short- and long-term outcomes of kidney transplant recipients in terms of graft and patient survival. However, PTDM often goes undiagnosed is underestimated or poorly managed. A diagnosis of PTDM should be delayed until the patient is on stable maintenance doses of immunosuppressive drugs, with stable kidney graft function and in the absence of acute infections. Risk factors for PTDM should be assessed during the pre-transplant evaluation period, in order to reduce the likelihood of developing diabetes. The oral glucose tolerance test is considered as the gold standard for diagnosing PTDM, whereas HbA1c is not reliable during the first months after transplantation. Glycaemic targets should be individualised, and comorbidities such as dyslipidaemia and hypertension should be treated with drugs that have the least possible impact on glucose metabolism, at doses that do not interact with immunosuppressants. While insulin is the preferred agent for treating inpatient hyperglycaemia in the immediate post-transplantation period, little evidence is available to guide therapeutic choices in the management of PTDM. Metformin and incretins may offer some advantage over other glucose-lowering agents, particularly with respect to risk of hypoglycaemia and weight gain. Tailoring immunosuppressive regimens may be of help, although maintenance of good kidney function should be prioritised over prevention/treatment of PTDM. The aim of this narrative review is to provide an overview of the available evidence on management and prevention of PTDM, with a focus on the available therapeutic options.