One in three Malaysian bypass patients develops acute kidney injury, study finds

Acute kidney injury struck roughly one in three patients undergoing coronary artery bypass grafting at a tertiary Malaysian hospital, according to a five-year retrospective cohort study published in BMC Nephrology.

Among the 551 patients, whose mean age was 62.3 years and 82.4 percent of whom were male, cardiac surgery-associated acute kidney injury occurred in 185 patients, or 33.6 percent. Using the KDIGO 2012 criteria, the researchers staged the injury as stage 1 in 69.2 percent of affected patients, stage 2 in 11.4 percent, and stage 3 in 19.5 percent. Outcomes worsened sharply with each advancing stage: in-hospital mortality was 2.3 percent for stage 1, 0.0 percent for stage 2, and 47.2 percent for stage 3, while intensive care and hospital lengths of stay increased and renal recovery declined with rising severity, with p values below 0.001 for all these trends.

In adjusted multivariable models, the variables independently associated with acute kidney injury were lower haemoglobin, higher baseline creatinine, emergency surgery, older age, and longer cardiopulmonary bypass time. The severe kidney injury and mortality models were exploratory and underpowered because of limited event numbers, but in them lower haemoglobin and emergency surgery were associated with severe injury, and higher Sequential Organ Failure Assessment scores and lower haemoglobin were associated with in-hospital mortality. Perioperative anaemia and prolonged bypass time emerged as the most consistent observational risk factors across multiple outcome models.

The team evaluated four preoperative risk scores—Mehta, Cleveland Clinic, the Simplified Renal Index, and Leicester—for their ability to predict severe acute kidney injury and the need for continuous renal replacement therapy. All four showed moderate discrimination, with areas under the receiver operating characteristic curve ranging from 0.707 to 0.763 for continuous renal replacement therapy and from 0.720 to 0.748 for severe injury. Their negative predictive values were high, exceeding 97.9 percent, but their positive predictive values were poor, ranging from 7.2 to 16.4 percent. The authors note that the high negative predictive values reflect both the low prevalence of these outcomes in the cohort and the scores’ performance, meaning the scores may be more useful for ruling out risk than for identifying patients who will develop severe injury.

The study also included a prespecified descriptive subgroup analysis of the 24 patients who required dialysis, comparing outcomes between those who started continuous renal replacement therapy within 24 hours of the kidney injury diagnosis and those who started later. Six patients were in the early group and 18 in the late group. No statistically significant difference in mortality or renal recovery was observed between the two groups, but the researchers emphasise that this analysis was substantially underpowered and is presented as hypothesis-generating only.

The authors describe their work as the first systematic characterisation of cardiac surgery-associated acute kidney injury risk prediction performance in a Southeast Asian coronary artery bypass grafting population. They note that contemporary data from the region have been sparse and that established preoperative risk scores had not previously been externally validated there. The study was conducted at a single tertiary Malaysian centre, which limits how broadly the findings can be generalised, and the severe injury, mortality, and dialysis timing analyses were all constrained by small numbers of events.

Overall, the findings confirm that acute kidney injury after bypass surgery is a frequent and serious complication in this multi-ethnic Malaysian cohort, affecting one-third of patients and conferring markedly worse outcomes as severity increases.

Subject of Research: Incidence, outcomes, and validation of preoperative risk scores for cardiac surgery-associated acute kidney injury in a Malaysian coronary artery bypass grafting cohort

Article Title: Cardiac surgery–associated acute kidney injury in Malaysia: incidence, outcomes, and validation of four preoperative risk scores in a coronary artery bypass grafting cohort (KARMA study)

Article References: Lau, C. H., Bay, S. S., Lee, Y. W., Gan, C. C., Poon, K. V., Liyana, E., Jalalonmuhali, M., Krishnasamy, S., & Adnan, W. A. H. W. M. (2026). Cardiac surgery–associated acute kidney injury in Malaysia: incidence, outcomes, and validation of four preoperative risk scores in a coronary artery bypass grafting cohort (KARMA study). BMC Nephrology. https://doi.org/10.1186/s12882-026-05332-y

Image Credits: AI Generated

DOI: 10.1186/s12882-026-05332-y

Keywords: acute kidney injury, coronary artery bypass grafting, cardiac surgery, risk scores, Malaysia, KDIGO criteria, renal replacement therapy, in-hospital mortality, cardiopulmonary bypass, anaemia, BMC Nephrology, retrospective cohort