Which factor increases the rate of filtration and urine formation?

• A. Dehydration
• B. Increase in blood pressure
• C. Decreased renal blood flow
• D. Increased ADH release

Answer: (B)

The main idea is glomerular filtration rate (GFR), which depends on renal blood flow and the pressure inside the glomerular capillaries. When systemic blood pressure increases, more blood reaches the kidneys and the glomerular capillary pressure rises, which boosts GFR and leads to more filtrate and potentially more urine formation. Dehydration lowers circulating volume and renal perfusion, reducing GFR. A decrease in renal blood flow directly lowers filtration. Antidiuretic hormone (ADH) mainly promotes water reabsorption in the collecting ducts, increasing water conservation rather than increasing the rate of filtration. So, higher blood pressure is the factor that increases filtration rate and urine formation.