A patient's urine is collected for 2 hours, and the total volume is 600 milliliters during this time. Her urine osmolarity is 150 mOsm/L, and her plasma osmolarity is 300 mOsm/L. What is her "free water clearance"?
Free water clearance is calculated as: urine flow rate (600 ml/2 h, or 5 ml/min) - osmolar clearance (urine osmolarity x urine flow rate/plasma osmolarity). Therefore, free water clearance is equal to +2.5 ml/min.
+5.0 ml/min
+2.5 ml/min
0.0 ml/min
-2.5 ml/min
Excretory System