Small Creatinine Rises After Elective Surgery Linked to Higher Mortality

A small absolute increase in creatinine after major elective surgery was associated with a consistent rise in 90-day mortality across most levels of baseline kidney function, according to a multinational cohort study published in Clinical Kidney Journal.

Under current acute kidney injury (AKI) criteria, it remains debated whether small absolute creatinine increases are associated with higher mortality in patients with low baseline estimated glomerular filtration rate (eGFR) and whether they carry prognostic value comparable to relative increases, the investigators noted. They studied major elective surgery because creatinine is routinely measured before and after surgery regardless of clinical status.

The study pooled population-wide data from Canada, Denmark, Scotland, and Wales on 311,975 major elective surgical procedures in 279,554 adults, with 11,568 deaths within 90 days. The investigators assessed the highest absolute creatinine increase within 2 days and the highest relative increase within 7 days during the first postoperative week, and estimated 90-day mortality standardized for age, sex, year, and surgery type.

Compared with no change in creatinine, a 0.3 mg/dL (26.5 µmol/L) absolute increase was associated with an increase of 2.2 to 3.3 percentage points in standardized mortality for baseline eGFR between 15 and 90 mL/min/1.73 m², with a higher increase above 90 mL/min/1.73 m² and a lower increase below 15 mL/min/1.73 m². A 50% relative increase and a 0.3 mg/dL absolute increase were associated with the same absolute increase in mortality around an eGFR of 90 mL/min/1.73 m². Below 30 mL/min/1.73 m², however, the 50% relative increase was associated with a substantially higher absolute increase in mortality.

The investigators noted that patients had to be deemed fit for elective surgery, that the findings may not apply to creatinine increases in nonsurgical settings, and that estimates were uncertain where eGFR was below 15 mL/min/1.73 m². They concluded that small absolute creatinine increases remain a relevant component of AKI criteria, but that the higher excess mortality associated with a 50% increase at low eGFR should be emphasized in future guidelines.

Source: Munch PV, Sawhney S, Heide-Jørgensen U, et al. Creatinine increases have consistent and differential prognostic impact across kidney function. Clin Kidney J. Published online 2026. doi:10.1093/ckj/sfag319