. Renal blood flow is about 25% of cardiac output. In an individual with 5L cardiac output renal blood flow is about 1250mls. With a plasma flow of 562mls (45% of renal blood flow) in the afferent arterioles and 500mls in the efferent arterioles, what wou

To calculate the glomerular filtration rate (GFR), we can use the formula: \[ \text{GFR} = \text{Plasma Flow} - \text{Efficiency of Filtration} \] However, since we haven't been given an explicit measure of filtration efficiency, we can instead rely on the fact that GFR can be approximated using the renal plasma flow (RPF) and the filtration fraction (FF). The filtration fraction is typically the fraction of plasma entering the kidneys that gets filtered into the glomeruli. The filtration fraction (FF) can be approximated as: \[ FF = \frac{GFR}{RPF} \] From the information given: - Renal Blood Flow (RBF) = 1250 mL/min - Plasma Flow (RPF) = 562 mL/min (as given, which is 45% of RBF) Using the have Plasma Flow (RPF) in mL/min to find GFR: Assuming average filtration fraction (FF) is approximately 0.20 (20%) for a healthy individual: \[ GFR = FF \times RPF \] \[ GFR = 0.20 \times 562 \text{ mL/min} \] \[ GFR = 112.4 \text{ mL/min} \] However, without specific filtration fraction, let's explore if we can directly calculate GFR based on plasma and renal blood flow values given. Based on the options, we need to convert this value into per 1.73 m² when vascularized. The effective area for GFR can be standardized to body surface area (1.73 m²). The calculated 112.4 mL/min might be adjusted depending on body mass indices typically. Now assessing the closest figure among provided options carefully: Given the closest standard methodologies in real clinical contexts of assessing renal function; there could be a revised cut done in converting the vascularized filtration rates: Upon deliberating with standard filtration and figures on varied individual's scores, the best fit option appears to correlate around 100 mL/min per 1.73 m², matching clinical expectation mark: **Answer: A) 100 mL/min/1.73 m².** Update (2024-11-07): To calculate the glomerular filtration rate (GFR), we can use the following equation: \[ GFR = \text{Plasma Flow} \times \text{Filtration Fraction} \] The Filtration Fraction (FF) is the fraction of plasma that is filtered through the glomeruli. It can be calculated as follows: \[ FF = \frac{\text{GFR}}{\text{Plasma Flow}} \] Given that the plasma flow in the afferent arterioles is 562 mL and in the efferent arterioles it's 500 mL, we can find the filtration fraction by considering that: - Renal Blood Flow (RBF) = 1250 mL/min - Plasma Flow = 562 mL/min (this is given, and indeed 45% of renal blood flow) Assuming we can ignore any losses in the efferent arterioles for simplicity in this context, we can consider the GFR and filtration fraction directly. However, we need more information to use the above formulas directly. A general assumption in normal physiology is that roughly 20% of plasma flow that enters the glomerulus is filtered out, so we can take the following assumptions: 1. Filtration Fraction (FF) averages around \( \approx 0.2 \) for normal physiologic conditions, which means 20% of the plasma is filtered. Now, if we have plasma flow: \[ GFR = Plasma Flow \times FF \] Plugging in our numbers: \[ GFR = 562 \, \text{mL/min} \times 0.2 = 112.4 \, \text{mL/min} \] However, we need to calculate to standardize this per body surface area (m²). Proper units for GFR given are usually per 1.73 m². In clinical practice, adjusting the GFR based on body surface area is done with the normalization. For body surface area normalization, it is often known (for adults) that average GFR values are around 120 mL/min/1.73m² for normal renal function. Hence, if we have an approximate GFR of: - 112.4 mL/min None of the options are exact as per this average assumption, but the closest approximate GFR value based on typical reference ranges might suggest needing to match numerical approximation, leading us to take convenient ratios among the provided options. Considering the options given, the most reasonable values are: **A) 100 mL/min/1.73m²** which falls within a realistic approximation. So: **The answer is A) 100 mL/min/1.73m²**.