Proteinuria Helps Predict Complications Following Bypass Surgery

Patients with mild or heavy proteinuria are more likely to experience cardiac surgery associated acute kidney injury (CSA-AKI) after coronary artery bypass grafting (CABG), according to a new study.

Researchers at the National Taiwan University Hospital (Yun-Lin Branch, Douliou City, Taiwan) studied 1,052 adult patients undergoing CABG at the Yun-Lin Branch and its two affiliate hospitals between 2003 and 2007. Kidney injury associated with the surgery arose in 183 (17.4%) of the patients, with 50 patients (4.8%) requiring renal replacement therapy. Patients with mild proteinuria (trace to 1+) were 1.66 times more likely to experience CSA-AKI when compared with patients who did not have proteinuria. Those patients with more severe proteinuria (2+ to 4+) were 2.30 times more likely to experience CSA-AKI, and 7.29 times more likely to need dialysis or a kidney transplant. The study was published early online on November 29, 2010, in the Journal of the American Society of Nephrology.

"We have found that proteinuria is potentially a risk factor of postoperative acute kidney injury; however, this simple test is usually neglected in current practice,” said study coauthor Kwan-Dun Wu, MD, PhD. "These findings should motivate clinicians to become more concerned about the presence of low quantities of protein in the urine.”

CSA-AKI is one of the most significant and severe complications after cardiac surgery, with estimates of its incidence ranging from 1-30%. In its most severe form, CSA-AKI necessitates renal replacement therapy and has a mortality rate of 50% - 60%. The pathogenesis of CSA-AKI involves multiple pathways, including hemodynamic, inflammatory, and nephrotoxic factors, which also overlap each other in leading to the kidney injury.

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