Rosh Internal Medicine Boost Practice Exam

What is the expected laboratory finding in a patient suffering from dehydration and renal failure?

1. Low electrolytes

2. High creatinine

3. Normal electrolyte balance

4. Low blood urea nitrogen (BUN)

The correct answer is: High creatinine

In the context of dehydration and renal failure, an increase in creatinine levels is expected. Creatinine is a waste product generated from muscle metabolism, and its levels in the blood typically reflect kidney function. When the kidneys are functioning appropriately, they filter out creatinine, maintaining its levels within a normal range. However, in cases of renal failure, the kidneys are less effective at removing creatinine from the bloodstream, resulting in elevated serum creatinine levels. Additionally, dehydration contributes to this phenomenon by concentrating the blood, which can further elevate the levels of various metabolites, including creatinine. Therefore, when assessing a patient with dehydration and renal impairment, one would anticipate high creatinine levels as a reflection of the reduced renal function and the body's decreased ability to excrete waste products.