Prescribing Safety Assessment (PSA) Practice Exam

Post-renal AKI generally shows which pattern in biochemical disturbances?

1. Urea rises more than creatinine

2. Urea rises less than creatinine

3. Both substances fall

4. Only creatinine rises

The correct answer is: Urea rises less than creatinine

In post-renal acute kidney injury (AKI), the pattern of biochemical disturbances typically shows that urea rises more than creatinine. This occurs due to the body's response to an obstruction in the urinary tract that hinders the excretion of waste products. When there is a blockage, the renal tubules are less able to excrete urea, leading to a more pronounced accumulation of urea in the blood compared to creatinine. The kidneys continue to filter creatinine, albeit at a reduced rate, so its rise in the serum is not as significant as that of urea. This distinction is primarily due to how these substances are processed in the kidneys; urea is subject to more active reabsorption in the renal tubules during times of stress or injury, especially in the presence of obstruction. A pattern in which urea rises less than creatinine would not typically be observed in post-renal AKI. In scenarios where both substances fall, it indicates kidney dysfunction but not specifically the post-renal type. Lastly, a situation where only creatinine rises does not align with the common biochemical behaviors observed in post-renal AKI, as both substances generally reflect the renal handling of waste under obstructive circumstances.