Lecture Notes: Renal Physiology
Introduction
- Speaker: Pediatric resident, soon-to-be fellow in pediatric intensive care
- Focus: High-yield renal physiology for USMLE preparation
- Goals: Integrative, active learning; community-oriented approach
Ground Rules
- Mute your audio
- Post questions in the chat; will be addressed at the end
Importance of Renal Physiology
- Renal physiology is a central topic for USMLE exams
- Medicine transcends borders, appealing to an international audience
Key Concepts
Functional Organization of the Kidney
- Nephron: Basic functional unit
- Types: Juxta medullary (long loops into medulla), Cortical (majority)
- Susceptibility: Medulla and proximal tubule vulnerable to ischemic injury
- Vasa Recta: Part of peritubular capillary system, slower flow, lower medullary pO2
Renal Perfusion
- Kidneys receive 20-25% of cardiac output
- Example: Calculating renal blood flow in heart failure
Efferent and Afferent Arterioles
- Efferent Arteriole: Controlled by angiotensin II, affects GFR
- Afferent Arteriole: Prostaglandins keep it open
- NSAIDs reduce prostaglandins, affect renal blood flow
GFR and Renal Plasma Flow
- GFR Measurement: Inulin (ideal), Creatinine (practical, overestimates by 10%)
- Renal Plasma Flow Measurement: PAH (underestimates by 10%)
- Filtration Fraction: GFR/renal plasma flow; normal ~20%
Tubular Physiology
Proximal Convoluted Tubule
- Major site for reabsorption (sodium, glucose)
- Conditions: Fanco ni Syndrome, Diabetes (SGLT2 inhibitors)
Loop of Henle
- Descending Limb: Water permeable
- Thick Ascending Limb: Electrolyte reabsorption (sodium-potassium-2chloride transporter)
Distal Convoluted Tubule
- Sodium-chloride symporter affected by thiazides
- Parathyroid hormone increases calcium reabsorption here
Collecting Duct
- Principal Cells: Affected by aldosterone (sodium reabsorption) and ADH (water reabsorption via aquaporins)
- Intercalated Cells: Acid-base regulation, affected by aldosterone
Applications and Clinical Correlations
- NSAIDs and renal function
- Diuretics: Loop (furosemide) vs. Thiazide
- Aldosterone and its effects on acid-base balance
- Glucose handling and Splay phenomenon
Conclusion
- Upcoming Webinar: Focusing on high-yield missed concepts from USMLE
- Stay positive and proactive in preparation
- Connect via social media for daily questions and updates
Call to Action
- Consider joining the upcoming review session
- Write a review if you found the lecture valuable
These notes aim to capture the essence of the lecture and serve as a study aid for mastering renal physiology concepts vital for the USMLE.