What is the clearance of a substance when its concentration in the plasma is 10 mg/dL, its concentration in urine is 100 mg/dL, and urine flow is 2 mL/min?
**Core Concept**
The underlying principle being tested is the concept of renal clearance, which is the volume of plasma from which a substance is completely removed per unit time. Clearance is a measure of the kidney's ability to remove waste products from the blood. It is calculated using the formula: Clearance = (Urine concentration x Urine flow) / Plasma concentration.
**Why the Correct Answer is Right**
To calculate the clearance of the substance, we use the given values: urine concentration (100 mg/dL), plasma concentration (10 mg/dL), and urine flow (2 mL/min). First, we need to ensure the units are consistent, typically converting concentrations to mg/mL since 1 dL = 100 mL. Thus, urine concentration is 1 mg/mL (100 mg/dL = 1 mg/mL) and plasma concentration is 0.1 mg/mL (10 mg/dL = 0.1 mg/mL). The formula then gives us Clearance = (1 mg/mL x 2 mL/min) / 0.1 mg/mL = 20 mL/min.
**Why Each Wrong Option is Incorrect**
**Option A:** This option would be incorrect because it does not match the calculation based on the provided formula and values.
**Option B:** Similarly, this option does not align with the calculated clearance using the given concentrations and urine flow.
**Option C:** This option is also incorrect as it does not reflect the result of the clearance calculation.
**Option D:** This is the correct calculation as shown, but let's assume for explanation purposes that if another option matched our calculation, this would be incorrect due to not being the calculated answer.
**Clinical Pearl / High-Yield Fact**
Renal clearance is a critical concept in understanding how the kidneys function and how drugs are eliminated from the body. The clearance of a substance can give insights into renal function and drug dosing, especially for drugs that are primarily excreted by the kidneys.
**Correct Answer:** Correct Answer: D. 20 mL/min