A 76-year-old's creatinine has risen from 95 to 310 over three days following a CT with contrast and an emergency laparotomy. How would you assess and manage this?

Question

A 76-year-old man on ramipril and naproxen underwent CT with contrast followed by emergency laparotomy for a perforated diverticulum. Day 3 post-operatively his creatinine is 310, urine output 15 ml/hour, and he is oedematous.

Accepted Answer

I would start by staging this formally: a rise from a baseline of 95 to 310 is more than a threefold increase, which is KDIGO stage 3, and his urine output of 15 ml/hour compounds that. I would then work through pre-renal, intrinsic and post-renal causes rather than assuming a single culprit. Post-renal first because it is quickly excluded and quickly reversible: a bladder scan at the bedside and a renal ultrasound within 24 hours, which is an explicit NICE standard. Pre-renal is the most likely dominant mechanism here — sepsis from the perforation and perioperative hypoperfusion — and I would say that the contrast is probably a much smaller contributor than it appears, since the modern evidence is that contrast-associated AKI is considerably less common than was historically believed. Volume assessment needs care: he is oedematous, but oedema does not mean he is intravascularly full, so I would assess capillary refill, JVP, passive leg raise response, lactate and the response to a small fluid challenge rather than reaching for a diuretic. I would stop the nephrotoxins by name — ramipril and naproxen — and review every drug on the chart for renal dosing, including antibiotics and low molecular weight heparin. I would dip and microscope the urine; blood and protein would raise an intrinsic renal cause and prompt a renal screen and nephrology discussion. I would look hard for ongoing sepsis or an undrained collection, because a source that has not been controlled is the commonest reason for a post-operative AKI not to recover. I would monitor potassium, bicarbonate and fluid balance closely, and my criteria for renal replacement therapy would be refractory hyperkalaemia, severe metabolic acidosis, fluid overload unresponsive to treatment, or uraemic pericarditis or encephalopathy. I would involve nephrology and critical care early rather than at the point of failure.

Contrast-Associated and Post-Operative AKI

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