Acute kidney injury in pregnancy — structured oral station (12 minutes)

Opening prompt — "What do you make of these numbers?"

Model response — defend the pregnant baseline: [1][5]

• "This is acute kidney injury stage 3 on a pregnant baseline. Her baseline creatinine of 64 micromol/L is at the upper edge of normal pregnant range (44–62); a rise to 158 micromol/L is more than 2.5 times baseline, with oliguria under 0.5 mL/kg/h. She meets stage 3 by both the creatinine and the urine-output criteria."
• "The metabolic acidosis (pH 7.28, bicarbonate 15) and the hyperkalaemia (6.2 mmol/L) are the immediate threats. I would treat both now and call nephrology."
• "The cause is almost certainly multifactorial — hypoperfusion from the PPH (acute tubular necrosis), sepsis from the wound infection, and possibly a contribution from nephrotoxic medication."[1][2]

Examiner is listening for: KDIGO applied against the pregnant baseline, recognition of stage 3 AKI, the immediate threats (acidosis and hyperkalaemia), and the multi-hit differential. [1]

Probe 1 — "What is the pregnant baseline and why does it matter?"

• "The pregnant baseline creatinine is 44–62 micromol/L because GFR rises 50% from 14 weeks. Above 75 micromol/L (0.85 mg/dL) is AKI in pregnancy — the value sits inside the non-pregnant reference range and is dismissed as 'normal'."[1][5]
• "The high-flow state means the kidney is dependent on the high perfusion; any loss of flow translates into a larger absolute fall in filtration than in the non-pregnant patient."[2][5]
• "The physiological hydronephrosis of pregnancy and the dilated right renal collecting system predispose to pyelonephritis and may produce a spurious diagnosis of obstruction on ultrasound."[5]

Probe 2 — "How would you manage the immediate threats?"

• "Hyperkalaemia 6.2 mmol/L with acidosis — calcium gluconate 10 mL of 10% IV for cardiac membrane stabilisation, insulin-dextrose to shift potassium intracellularly, salbutamol nebuliser, bicarbonate for the acidosis. Recheck potassium in 30 minutes."[4]
• "Fluid management: cautious — she has had PPH and is now septic; she may leak. Small balanced crystalloid boluses, frequent reassessment of fluid status, aim for euvolaemia. Avoid hydroxyethyl starch. Avoid NSAIDs entirely."[2]
• "Antibiotics: review the co-amoxiclav — she has sepsis and AKI; consider broader cover (e.g., piperacillin-tazobactam or carbapenem) and adjust for renal function. Send blood, urine and wound cultures; check lactate."[2][4]

Probe 3 — "She continues to deteriorate — creatinine 195, potassium 6.7, pH 7.24. What now?"

• "She now meets the AEIOU criteria for renal replacement therapy — refractory hyperkalaemia (E), refractory metabolic acidosis (A), and likely fluid overload (O). I would call nephrology and ICU now and arrange RRT."[1][4]
• "Modality: continuous RRT preferred in the haemodynamically unstable woman; intermittent haemodialysis acceptable in the stable patient. Internal jugular access preferred; heparin anticoagulation or regional citrate in CRRT with calcium monitoring."[3][4]
• "Fetal considerations no longer apply — she is postpartum. But the postpartum woman is still physiologically pregnant for at least a week; re-set the thresholds."[3]

Probe 4 — "What about the underlying cause?"

• "Source hunt: examine the wound, the uterus (retained products, endometritis), the urine (pyelonephritis), the calves (DVT). Send focused cultures and inflammatory markers."[2]
• "Consider the thrombotic microangiopathies — postpartum aHUS can present in the days after delivery with microangiopathic haemolytic anaemia, thrombocytopenia and AKI. Send a smear for schistocytes, LDH, haptoglobin, ADAMTS13, complement panel. If aHUS is on the differential, eculizumab is time-critical — call haematology and nephrology now."[2]
• "In this case the precipitant is clear (PPH with sepsis) and the picture is consistent with multi-hit ATN, but the postpartum setting keeps aHUS on the differential until the smear and ADAMTS13 return."[2]

Probe 5 — "Her partner is at the bedside and frightened. How do you communicate?"

This is a scored domain, not a courtesy. Demonstrate it out loud: [1]

• Move to her eye level, use her name, brief plainly: "Your kidneys are struggling after the bleeding and the infection. We have a team here. We are giving you medicines to correct the salts in your blood, and we are preparing a kidney support treatment that filters the blood. I will keep telling you what is happening."
• Acknowledge fear, keep the partner informed, allocate a staff member to support them, and commit to a debrief afterwards.[1][6]