Treatment with Allopurinol is Associated with Lower Risk of Acute Kidney Injury in Patients with Gout: A Retrospective Analysis of a Nested Cohort

INTRODUCTION: Gout is characterized by recurrent episodes of acute inflammation of joint structures, called gout flares, and flares are commonly treated with nonsteroidal anti-inflammatory drugs (NSAIDs). The objective of the study was to evaluate risk factors associated with acute kidney injury (AKI) attributed to NSAIDs in a cohort of patients who were exposed to NSAIDs to treat gout flares prior to urate-lowering therapy. METHODS: Retrospective analysis of a nested cohort of 983 gout patients in whom general variables (age, gender, renal function, ethanol intake, hypertension, hyperlipidemia, diabetes, vascular events, diuretic use) and also variables related to gout and severity of gout (serum urate levels, number for flares per year, presence of tophi, joint distribution, X-ray involvement, previous urate-lowering therapy) were available for analysis. Outcomes considered were loss of renal function attributed to NSAID prescription following the RIFLE classification for (risk, injury, and failure) for acute renal events. Variables associated with increased risk in Kaplan–Meier survival analysis were tested with multivariable Cox survival analysis, using time from onset of gout to the event as time exposed to NSAIDs. RESULTS: Of 983 patients, 55 (5.6%) experienced AKI; the number of flares in the year previous to the renal event and polyarticular joint distribution were associated with higher risk of renal events. Other variables previously described in the literature, such as previous chronic renal disease, use of diuretics, and presence of previous vascular events, were also independently associated with increased risk of AKI. Interestingly, patients who had been previously prescribed allopurinol showed a lower risk of acute renal events. CONCLUSION: In addition to classic risk factors, the number of flares and extensive joint distribution were associated with higher risk for renal injury in patients with gout, while previous prescription of allopurinol was associated with lower risk.