Uric Acid and the Risks of Kidney Failure and Death in Individuals With CKD

Impact of Serum Uric Acid Levels on Outcomes following Renal Artery Revascularization in Patients with Renovascular Disease

BACKGROUND

Percutaneous transluminal renal angioplasty (PTRA) improves blood pressure (BP) and renal function only in selected patients with atherosclerotic renovascular disease (ARVD). Hyperuricemia is associated with elevated risk for hypertension and chronic renal disease, but its role in renovascular hypertension is unclear. We hypothesized that hyperuricemia negatively impacts renal and BP outcomes among patients with ARVD undergoing PTRA.

METHODS

This retrospective, observational cohort study included 94 patients with ARVD and preserved systolic cardiac function, who underwent PTRA at Mayo Clinic, Rochester, Minnesota. Renal, BP, and mortality outcomes were compared among patients according to their serum uric acid (SUA) levels. Multivariate analysis was used to determine significant predictors of renal, BP, and mortality outcomes after PTRA.

RESULTS

Compared to patients with normal basal SUA levels (≤5.7 mg/dl), patients with very high SUA (≥8.7 mg/dl) had lower baseline estimated glomerular filtration rate (eGFR), more extensive use of antihypertensive and diuretic drugs, increased baseline systolic blood pressure (SBP), and elevated left ventricular mass index. After PTRA, multiple logistic regression analysis showed that, compared to normal SUA, very high SUA was associated with decreased odds ratio (OR) of change in eGFR (adjusted OR=0.90; 95% confidence interval [CI], 0.86-0.95), but not of change in SBP. In multivariate linear analysis SUA independently predicted delta urine protein/creatinine ratio (β: 26.0; 95% confidence interval, 13.9 to 38.1).

CONCLUSION

Severe hyperuricemia in patients with AVRD may have a negative impact on outcomes of renal revascularization.

Comparison of efficacy and safety between febuxostat and allopurinol in early post-renal transplant recipients with new onset of hyperuricemia

What is known and objective

Febuxostat and allopurinol are xanthine oxidase inhibitors for urate‐lowering therapy. The efficacy and safety of febuxostat and allopurinol have been mostly reported in hyperuricemia patients with normal renal function. Here, we aimed to compare the effects of these two drugs in early post‐renal transplant recipients, focusing on evaluating the urate‐lowering effect and recovery of allograft renal function.

Methods

A retrospective cohort study was performed in early post‐renal transplant recipients with new onset of hyperuricemia receiving febuxostat or allopurinol therapy. Serum uric acid (UA) and estimated glomerular filtration rate (eGFR) were detected on days 3, 7 and 15 and months 1, 3 and 6 after therapy initiation. Liver and blood functions were monitored and other adverse events were recorded.

Results and discussion

A total of 48 and 33 patients were enrolled in the febuxostat and allopurinol groups, respectively. Significant UA‐lowering effects were observed on day 3 in both groups. Febuxostat caused a more rapid UA decline, starting on day 3 and lasting for 1 month. The most apparent contrast was found in UA level (267.25 ± 93.66 vs 334.18 ± 96.56 μmol/L, P = 0.003) on day 7; 62.5% and 30.3% of patients achieved target UA level in febuxostat and allopurinol groups respectively on day 3 (P = 0.004), but there was no significant difference between two groups from days 15 to months 6. The median times to achieve target UA level were 3 and 5 days in febuxostat and allopurinol groups respectively (P = 0.002). The eGFR levels and recovering rates were gradually upregulated but no significant differences were found between two groups. No abnormities related to febuxostat or allopurinol were observed.

What is new and conclusion

This is the first comprehensive evaluation of UA‐lowering effects of febuxostat and allopurinol in early post‐renal transplant recipients. Febuxostat caused a marginally quicker serum UA‐lowering effect than allopurinol, but there was no advantage for long‐term use of febuxostat. The drugs had no significant differences in impacting renal allograft function recovery, and both were well tolerated.

Association between post-transplant serum uric acid levels and kidney transplantation outcomes

Background

Serum uric acid (UA) level has been reported to be associated with chronic allograft nephropathy and graft failure in patients who undergo kidney transplantation (KT). However, the role of serum UA level in renal graft survival remains controversial.

Objective

This study aimed to investigate the effect of mean serum UA level during two different post-KT periods on long-term renal graft outcomes in a large population cohort in which living donor KT prevails.

Material and methods

A retrospective cohort study was performed using KT data prospectively collected at a single institution. Patients (n = 2,993) were divided into low-, normal-, and high-UA groups according to the mean serum UA level within the first year (1-YR) and 1–5 years (5-YR) after transplantation.

Results

In the 1-YR Cox proportional hazards analysis, the low- and high-UA groups had a significantly decreased and increased risk, respectively, for overall graft failure (OGF), death-censored graft failure (DCGF), and composite event (return to dialysis, retransplantation, death from graft dysfunction, and 40% decline in estimated glomerular filtration rate) compared with the normal-UA group. Similarly, in the 5-YR analysis, the low-UA group had a significantly reduced risk of DCGF compared with the normal-UA group, whereas the high-UA group had a significantly increased risk of all three graft outcomes. In a marginal structural model, hyperuricemia had a significant causal effect on worsening graft outcomes, with consideration of all confounding variables (OGF: hazard ratio [HR] 2.27, 95% confidence interval [CI] 1.33–3.78; DCGF: HR 2.38, 95% CI 1.09–4.9; composite event: HR 3.05, 95% CI 1.64–5.49).

Conclusions

A low-to-normal serum UA level within the first year and 1–5 years after KT is an independent factor for better renal allograft outcomes in the long-term follow-up period rather than high serum UA level.

Cardiotoxicity of Uremic Toxins: A Driver of Cardiorenal Syndrome

Cardiovascular disease (CVD) is highly prevalent in the setting of chronic kidney disease (CKD). Such coexistence of CVD and CKD—the so-called “cardiorenal or renocardiac syndrome”—contributes to exponentially increased risk of cardiovascular (CV) mortality. Uremic cardiomyopathy is a characteristic cardiac pathology commonly found in CKD. CKD patients are also predisposed to heart rhythm disorders especially atrial fibrillation. Traditional CV risk factors as well as known CKD-associated CV risk factors such as anemia are insufficient to explain CV complications in the CKD population. Accumulation of uremic retention solutes is a hallmark of impaired renal excretory function. Many of them have been considered inert solutes until their biological toxicity is unraveled and they become accepted as “uremic toxins”. Direct cardiotoxicity of uremic toxins has been increasingly demonstrated in recent years. This review offers a mechanistic insight into the pathological cardiac remodeling and dysfunction contributed by uremic toxins with a main focus on fibroblastic growth factor-23, an emerging toxin playing a central role in the chronic kidney disease–mineral bone disorder, and the two most investigated non-dialyzable protein-bound uremic toxins, indoxyl sulfate and p-cresyl sulfate. Potential therapeutic strategies that could address these toxins and their relevant mediated pathways since pre-dialysis stages are also discussed.