Acute kidney injury in pregnancy

A 32-year-old woman, day 2 post emergency caesarean for severe preeclampsia at 34 weeks, is oliguric despite fluid challenge. Her creatinine has risen from 62 to 124 micromol/L overnight. The registrar charts "stable renal function" because the value sits inside the non-pregnant reference range. Both numbers are wrong — she has doubled her creatinine on a pregnant baseline, she has acute kidney injury, and the cause is almost certainly evolving HELLP or a retroperitoneal bleed from the surgery. The pregnant kidney is a high-flow kidney; any loss of that flow is pathology, not physiology. This topic is the recognition and the response.^[1][2][6]

Overview and definition

Pregnancy-related AKI is a sudden reduction in glomerular filtration, defined by the KDIGO criteria — rise in serum creatinine or fall in urine output — applied against the pregnant baseline. The pregnancy-specific twist is that the baseline itself is altered: GFR is up 50%, creatinine is typically 44–62 micromol/L, and what counts as "normal" in a non-pregnant patient is already renal impairment in a pregnant one.^[1][13]

The KDIGO definition, summarised in Kellum 2013:^[1]

• Stage 1: rise in serum creatinine by 26.5 micromol/L (0.3 mg/dL) within 48 hours, or a rise to 1.5–1.9 times baseline.
• Stage 2: rise to 2.0–2.9 times baseline.
• Stage 3: rise to 3.0 times baseline, or rise to 354 micromol/L (4.0 mg/dL) or more, or initiation of renal replacement therapy, or (in patients under 18) a fall in eGFR to under 35 mL/min/1.73 m².^[1]
• Urine output criteria: under 0.5 mL/kg/h for 6–12 hours (stage 1); under 0.5 for 12 hours or more (stage 2); under 0.3 for 24 hours or more, or anuria for 12 hours (stage 3).^[1]

The pregnant baseline matters most at the lower end. A 26.5 micromol/L rise from a baseline of 50 lands the woman at 76 micromol/L — already AKI stage 1, and already a warning sign that demands investigation, not reassurance.^[1][13]

References14ShowHide

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