American Board of Internal Medicine (ABIM) Certification Practice Exam

What condition is the strongest nonmodifiable predictor of acute kidney injury after cardiac surgery?

1. Hypertension

2. Diabetes Mellitus

3. Preexisting chronic kidney disease

4. Heart Failure

The correct answer is: Preexisting chronic kidney disease

The strongest nonmodifiable predictor of acute kidney injury (AKI) after cardiac surgery is preexisting chronic kidney disease (CKD). Chronic kidney disease is characterized by a gradual loss of kidney function over time, which alters the kidneys' resilience to stressors such as the physiological changes that occur during cardiac surgery. When patients with CKD undergo cardiac surgery, their kidneys are already compromised, making them less capable of handling additional insult from factors such as hypotension during the procedure, nephrotoxins (including certain medications), or reduced renal perfusion. This heightened susceptibility significantly increases the likelihood of developing acute kidney injury in such patients. While conditions such as hypertension, diabetes mellitus, and heart failure can also contribute to the risk of AKI, they serve more as risk factors or comorbidities rather than being as directly predictive as CKD itself. Hypertension and diabetes can lead to kidney damage over time but do not necessarily predispose to acute changes in the same way that preexisting chronic changes in kidney function do. Heart failure can influence renal perfusion and function but is generally not as strong a predictor of post-operative acute kidney injury as chronic kidney disease.