Hospitalized patients with high serum uric acid (SUA) levels have greater risks for acute kidney injury (AKI), non-recovery from AKI, and death than patients with low levels, new study findings confirm.
Of 18,444 patients hospitalized in 2013 at Seoul National University Bundang Hospital in Gyeonggi-do, South Korea, AKI developed in 1254 (12.9%) men and 944 (10.8%) women over a mean 7.5 and 7.7 days, respectively, according to Kidney Disease Improving Global Outcomes definitions. Stage 3 AKI and AKI requiring dialysis occurred in 210 (2.2%) and 59 (0.6%) of men, respectively, and 153 (1.7%) and 36 (0.4%) of women, respectively.
Investigators grouped SUA levels into quartiles for men (less than 4.5, 4.5–5.5, 5.6–6.7, and greater than 6.7 mg/dL) and women (less than 3.6, 3.6–4.3, 4.4–5.3, and greater than 5.3 mg/dL). Men and women in the highest quartiles of uric acid had a significant 3.2-fold and 3.1-fold greater risk for AKI, respectively, than those in the lowest quartiles, Seung Seok Han, MD, PhD, of Seoul National University College of Medicine, and colleagues reported in Nephrology. In addition, men and women in the highest quartiles were, respectively, 2.0- and 2.4-fold less likely to experience recovery from AKI (defined as a return of serum creatinine to 1.2 times the baseline level and discontinuation of dialysis).
Men and women in the top quartile of uric acid had a significant 1.4- and 1.2-fold higher risk for all-cause mortality, respectively. Men in the top vs bottom quartile had a significant 2.1-fold increased risk of in-hospital mortality. The investigators adjusted for a range of confounders, including age, body mass index, cardiovascular disease, estimated glomerular filtration rate, surgical history, and uric acid-lowering agents. Causes of death were unknown, which was a study limitation.
“Based on the high risk of AKI and mortality in patients with hyperuricemia, serum uric acid levels should be monitored in hospitalized patients,” Dr Han and his colleagues stated. The team added that future research should investigate the potential benefits of uric acid-lowering agents.
Whether hyperuricemia leads to AKI or merely predicts it is still unknown. The researchers discussed several mechanisms underlying a possible relationship. Uric acid may damage tubular cells or promote renal vasoconstriction and reduced blood flow. It may stimulate pro-inflammatory cytokine expression or induce oxidative stress.
Kang MW, Chin HJ, Joo KW, et al. Hyperuricemia is associated with acute kidney injury and all-cause mortality in hospitalized patients. Nephrol. DOI:10.1111/nep.13559. Accepted manuscript.