Which statement about ultrafiltration rate is true?

• A. It is calculated by dividing the ultrafiltration volume by the treatment time
• B. It is equal to the dialysate flow rate
• C. It is equal to the blood flow rate
• D. It is independent of patient size

Answer: (A)

Ultrafiltration rate measures how quickly fluid is removed from the patient during dialysis. It is defined as the ultrafiltration volume divided by the treatment time, giving a rate in mL per hour (often expressed as mL/kg/hr to account for patient size). This rate is not the same as the dialysate flow rate, which is how fast dialysate moves through the machine, nor is it the blood flow rate, which is the rate of blood passing through the circuit. Patient size matters because UFR is frequently indexed to body weight to compare and set safe targets; larger patients may require removal of more fluid, but the rate must be kept within safe limits to avoid hypotension and other complications. In short, the correct statement reflects that UFR = UF volume / treatment time, with units and safety implications tied to patient size.