Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

25. The Urinary System

Renal Physiology: Regulation of Glomerular Filtration

Anatomy & Physiology

25. The Urinary System

Renal Physiology: Regulation of Glomerular Filtration

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Problem L3.A2

Textbook Question

Mr. Yao is a patient with kidney disease who presents to your clinic for monitoring. You notice on his chart that his GFR was estimated through inulin administration to be about 35 ml/min. What does this tell you about the health of his kidneys? Mr. Yao is taking a medication that is normally excreted from the body in the urine. You order blood work and find that the concentration of this medication in his plasma is much higher than normal. How does his decreased GFR explain the elevated level of medication in his plasma?

Verified step by step guidance

Step 1: Understand the concept of Glomerular Filtration Rate (GFR). GFR is a measure of how well the kidneys filter blood. A normal GFR is typically around 90-120 ml/min. A GFR of 35 ml/min indicates significantly reduced kidney function, which is consistent with kidney disease.

Step 2: Recognize the role of the kidneys in excreting medications. The kidneys filter waste products and medications from the blood into the urine. If kidney function is impaired, the filtration process is less efficient, leading to reduced excretion of medications.

Step 3: Relate decreased GFR to medication clearance. With a GFR of 35 ml/min, Mr. Yao's kidneys are filtering blood at a much slower rate. This means that the medication is not being removed from the plasma as effectively, causing its concentration in the blood to rise.

Step 4: Consider the implications of reduced medication excretion. The elevated plasma concentration of the medication could lead to toxicity or reduced therapeutic effectiveness. Adjustments to the medication dosage may be necessary to account for impaired kidney function.

Step 5: Highlight the importance of monitoring kidney function and medication levels. Regular blood work and GFR assessments are crucial for patients with kidney disease to ensure proper medication management and prevent complications.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Glomerular Filtration Rate (GFR)

GFR is a measure of how well the kidneys filter blood, specifically the volume of fluid filtered from the renal glomeruli into the Bowman's capsule per minute. A normal GFR is typically around 90-120 ml/min, and a GFR of 35 ml/min indicates significantly reduced kidney function, suggesting chronic kidney disease or acute kidney injury. This reduction in GFR can lead to the accumulation of waste products and medications in the bloodstream.

Renal Excretion of Medications

Many medications are eliminated from the body through renal excretion, which involves filtration, secretion, and reabsorption processes in the kidneys. When GFR is decreased, the kidneys are less effective at filtering these medications from the blood, leading to higher plasma concentrations. This can result in potential toxicity or adverse effects, as the body is unable to clear the drug efficiently.

Pharmacokinetics in Kidney Disease

Pharmacokinetics refers to how the body absorbs, distributes, metabolizes, and excretes drugs. In patients with kidney disease, altered pharmacokinetics can affect drug dosing and efficacy. With a decreased GFR, the clearance of renally-excreted medications is impaired, necessitating careful monitoring and potential dosage adjustments to avoid toxicity and ensure therapeutic effectiveness.

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