Lecture Notes on Renal System and CRRT

Introduction

• Presenter: Eddie Watson
• Purpose: Educational content on critical care, focusing on continuous renal replacement therapy (CRRT).
• Platform: ICU Advantage YouTube channel

Renal System Anatomy

• Kidneys:
  • Location: Retroperitoneal cavity, sides of the spine, between the 12th thoracic and 3rd lumbar vertebrae.
  • Right kidney is lower due to the liver.
• Kidney Layers:
  • Cortex: Outer layer
  • Medulla: Inner section
  • Renal Pelvis: Urine collection

Nephron Structure

• Functional Unit: Nephron (over 1 million in each kidney)
• Parts of Nephron:
  • Glomerulus: Capsule-like structure
  • Bowman’s Capsule: Surrounds the glomerulus
  • Proximal Tubule
  • Loop of Henle: Composed of thin descending, thin ascending, and thick ascending loops
  • Distal Convoluted Tubule
  • Collecting Tubule and Duct

Renal Blood Supply

• Blood Flow:
  • 20-25% of cardiac output to kidneys
  • Starts with renal artery from the aorta
  • Afferent arterioles enter the Bowman’s capsule, forming the glomerulus
  • Efferent arterioles exit the glomerulus, forming peritubular capillaries

Renal Physiology

• Main Functions:
  • Filter blood and form urine
  • Regulate water, electrolytes, waste, and acid-base balance
• Blood Flow Dynamics:
  • Afferent arteriole (larger diameter) creates high pressure in glomerulus
  • Efferent arteriole (smaller diameter) allows for filtration
  • Hydrostatic pressure allows water filtration
• Diffusion and Convection:
  • Diffusion: Particles move from high to low concentration
  • Convection: Solutes dragged by water filtration

Tubular Functions

• Proximal Tubule:
  • Reabsorption of water, potassium, sodium, chloride, glucose, and bicarbonate
  • Passive secretion of hydrogen ions
• Loop of Henle:
  • Cortical nephrons: Excretion and regulation
  • Juxtamedullary nephrons: Dilute or concentrate urine
  • Permeability depends on thickness
• Distal Convoluted Tubule:
  • Regulates blood pressure and solute absorption/excretion
  • Impacted by ADH for water reabsorption
  • Bicarb reabsorption and hydrogen ion secretion
• Waste Excretion:
  • BUN, uric acid, and creatinine

Importance of Understanding Renal Physiology

• Homeostasis Regulation:
  • Fluid balance, electrolyte, and solute balance
  • Acid-base balance
• Application to CRRT:
  • Mimic nephron functions in therapy

Conclusion

• Objective: Equip with renal system knowledge for understanding CRRT
• Next Steps: Further lessons on CRRT
• Community Engagement:
  • Encouragement to subscribe, like, and comment
  • Acknowledgment of channel and Patreon supporters
• Additional Content: Upcoming detailed CRRT series