Which statement best describes the mechanism of hemodialysis?

• A. Removal of waste products via an artificial circuit
• B. Filtering urine via kidneys
• C. Production of urine
• D. Secretion of insulin

Answer: (A)

Hemodialysis works by removing waste products through an artificial circuit that substitutes for kidney function. Blood is run outside the body through a dialyzer, where a semipermeable membrane separates blood from the dialysate. Small waste molecules, such as urea and creatinine, diffuse from the blood into the dialysate because they are in higher concentration in the blood. At the same time, excess fluid is removed by applying a pressure gradient (ultrafiltration), helping control fluid balance. The dialysate is formulated to carry away wastes while preserving essential substances. This process restores some of the kidney’s filtering role in patients with kidney failure. It does not produce urine, nor does it involve secretion of insulin.