Action Points

Gout is independently associated with both chronic kidney disease (CKD) and kidney stones, and patients with gout should be screened for CKD to offset CKD-related risks, a meta-analysis indicates.

In a systematic review and meta-analysis of epidemiological studies, the pooled prevalence estimate of CKD stage ?3 was 24% (95% CI 19%-28%), and self-reported kidney stones was 14% (95% CI 12%-17%) among individuals with gout compared with those without gout.

Furthermore, after adjustment for confounding variables, people with gout were more than twice as likely to have CKD ?3 at an odds ratio (OR) of 2.41 (95% CI 1.86-3.11).

Data from three studies were pooled to provide a prevalence estimate of CKD?4 of 2% (95% CI 0%-4%) in the setting of gout versus non-gout.

Patients with gout were also over 1.5 times more likely at an OR of 1.77 to ever have had kidney stones as those who do not have gout.

After adjusting for age, sex, diabetes, and hypertension, gout was also an independent risk factor for incident end-stage renal disease (ESRD) at a hazard ratio (HR) of 1.57 based on one study.

"To our knowledge, this is the first meta-analysis of associations between gout and CKD/nephrolithiasis," Matthew Roughley, MD, Keele University, Keele, Staffordshire, and colleagues report in Arthritis Research and Therapy.

"The main clinical implications of our findings are that patients with gout should be screened for CKD and that clinicians should be made aware of the associations between gout and CKD/nephrolithiasis."

Seventeen studies were included in the meta-analysis: seven in CKD; eight on kidney stones, and two studies which included both CKD and kidney stones.

Six studies provided suitable data to allow the investigators to ascertain the pooled prevalence of CKD stage ?3 in individuals with gout.

Four studies provided suitable data to calculate a pooled age and gender-adjusted OR of 1.87 (95% CI 1.25-2.80) between those with gout and the risk of nephrolithiasis.

As investigators note, previous epidemiological studies have shown that CKD is an independent risk factor for gout.

Yet renal damage can result from comorbid hypertension and diabetes, hyperuricemia-mediated endothelial dysfunction, and renovascular disease along with the use of NSAIDs, suggesting there are plausible mechanisms by which gout might predispose to CKD, they add.

"Inflammation in gout is increasingly recognized to persist in the intercritical period between acute attacks," the authors write, "raising the possibility that inflammatory mechanisms contribute to vascular risk, as has been proposed for other inflammatory arthropathies."

As with any systematic review, findings are dependent upon the size and the quality of the published literature, and only a small number of studies had examined the potential association between CKD or kidney stones and gout.

The small number of published studies thus raises the possibility of publication bias.

The majority of the studies included in the meta-analysis were also not designed with the primary aim of assessing the association between gout and CKD and kidney stones, the authors add.

Several studies also did not include control groups without gout and only reported the prevalence of CKD and kidney stones in gout but not the strength of association between the two.

There were also few prospective studies on the risk of CKD and kidney stones in gout so investigators could not draw firm conclusions about temporal aspects of these potential associations.

"Unless sought for, CDK usually progresses subclinically until reaching more advanced stages," investigators concluded.

"In view of this ... a presentation with gout in primary care should be viewed as a 'red flag' for CKD and should prompt screening for and treatment of both CKD and its associated risk factors such as hypertension and diabetes mellitus, which are also risk factors for gout."

Current national and international guidelines regarding CKD and nephrolithiasis do not recognize gout as a risk factor for these conditions.

As a consequence, only one in five people presenting to primary care with acute gout are screened for CKD within a month of presentation.

The authors declared they did not receive any support from any company for the work submitted, nor did they have any relationships with companies that might have an interest in the submitted work.

• Reviewed by F. Perry Wilson, MD, MSCE Assistant Professor, Section of Nephrology, Yale School of Medicine

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