April 4, 2016


O’Connor et al. have conducted the “first systematic examination of reports that assess the incidence of AKI after major abdominal surgery using consensus definitions of AKI” [1]. In this systematic review, 19 studies (16 retrospective case cohort studies, prospective observational studies, and one interrupted time series analysis) were explored. AKI was defined by either the AKIN, RIFLE, or KDIGO criteria.

The authors report a pooled incidence of 13.4% of AKI following major abdominal surgery. Among patients with post-operative AKI, 72 % of patients with AKI had Stage 1 or RIFLE-R, 17 % had Stage 2 or RIFLE-I and 11 % had Stage 3 or RIFLE-F.

The incidence of AKI was not significantly different based on consensus definition of AKI, surgical category, or inclusion of patients with pre-existing CKD. Overall mortality among patients with AKI following major abdominal surgery varied from 0.3% to 3.7%, with a 12.6 fold-relative risk of death compared to patients who developed did not develop AKI. Notably, the relative risk of mortality associated with AKI was significant considering the proportion with relatively mild AKI.
Four studies reported renal recovery in between 47% and 79% of patients. However, varying definitions of recovery and time scales, and adjustment for death make any firm conclusions difficult.

Despite strict inclusion criteria, there was significant heterogeneity in the incidence of AKI and its associations with mortality. As with all observational studies, it was only possible to demonstrate association rather than causality between AKI incidence and mortality. AKI was also associated with other post-operative complications (infective, cardiovascular, respiratory and pooled complications) and increased length of stay. It was not possible to ascertain the attributable risk of AKI on mortality, or to ascertain the relative risk of individual risk factors. Importantly, the relative risk of death associated with emergency surgery compared to elective surgery is likely to be significant, but was not explored in these studies. An ongoing large prospective observational study may address some of these points [2].

Despite these limitations, the authors conclude that across the spectrum of major abdominal surgery, with different patient backgrounds, AKI is relatively common and is associated with a number of complications including death. A basic understanding of the scale of the problem is required for quality improvement initiatives and research.

This article review was prepared by Nishkantha Arulkumaran on behalf of the NEXT Committee.


1.    O'Connor ME, Kirwan CJ, Pearse RM, Prowle JR: Incidence and associations of acute kidney injury after major abdominal surgery. Intensive Care Medicine 2016, 42(4):521-530.
2.    Collaborative ST: Outcomes After Kidney injury in Surgery (OAKS): protocol for a multicentre, observational cohort study of acute kidney injury following major gastrointestinal and liver surgery. BMJ open 2016, 6(1):e009812.


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