Notes on Renal Clearance
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Notes on Nephrology
Notes on Renal Clearance
What is Clearance?
• Clearance = volume of plasma that is completely cleared of the substance by kidneys per unit time.
• Clearance is determined by plasma concentration and excretion rate.
Clearance of some substances:
Glucose:
Normally 0; clearance rises as plasma concentration rises; as plasma concentration continues to rise, clearance increases approaching that of insulin but never being equal to that of insulin.
Insulin:
Always excreted; not metabolized, not reabsorbed, and not secreted. 100% insulin is freely excreted. The greater the water reabsorption, the greater the increase in insulin concentration in urine; meaning, greater water reabsorption decreases water excretion, which causes concentrated urine.
Creatinine:
Completely filtered and some is secreted; used to measure GFR in clinical settings.
PAH:
Clearance = renal plasma flow (RPF); as plasma concentration rises, carriers in nephrons reach saturation. As plasma concentration rises further, clearance = GFR. Some PAH is always secreted.
Additional Reading:
Basic Nephrology
1. Renal Control in Acid-Base Balance
2. Renal Processes
3. Renal Clearance
4. Regional Transport
5. What are the indications for hemodialysis?
Related Topics
1. Kidney Disorders
2. Histology of the Urinary System
3. Acid-Base Disturbance: Acidotic or Alkalotic? [Size: 427 kB; Format: PDF]
4. Abdominal Examination for Internal Medicine
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