💧

Understanding Renal Pathophysiology Basics

Apr 6, 2025

Lecture Notes: Introduction to Renal Pathophysiology

Presenter Information

  • Presenter: Dr. Bill Deal-Jones
  • Institution: Athabasca University, Faculty of Health Disciplines

Overview

  • Focus on diseases affecting the renal system.
  • Topics to be covered:
    • Kidney anatomy and basic physiology
    • UTIs
    • Glomerular diseases
    • Renal failure
    • Renal colic

Kidney Anatomy and Physiology

Kidney Structure

  • Location: Retroperitoneal organ in the abdominal cavity.
  • Attachment: Held against the dorsal wall by peritoneum.
    • More susceptible to trauma than mesentery-suspended organs.
  • Capsule: Outer connective tissue capsule called Glissis capsule.
  • Shape: Classic kidney bean shape due to the renal hilum.
    • Renal hilum: Indentation for major vessels (renal pelvis, ureter, renal vein) and entry for the renal artery.

Kidney Division

  • Cortex and Medulla: Delineated boundary between outer cortex and inner medulla.
  • Nephron: Main functional unit of the kidney.
    • Components:
      • Glomerulus and Bowman's capsule (Renal corpuscle): Located in the cortex.
      • Loop of Henle and Collecting Duct: Extend into the medulla.
    • Functions:
      • Filtration: Affected by mean arterial pressure; occurs between glomerulus and Bowman's capsule.
      • Reabsorption: Movement of solute and water from tubule lumen back into blood.
      • Secretion: Movement of molecules into the lumen of the nephron.

Nephron Structure

  • Components:
    • Bowman's capsule
    • Proximal convoluted tubule
    • Loop of Henle (Descending and Ascending limbs)
    • Distal convoluted tubule
    • Collecting duct

Vascular Network

  • Afferent arteriole enters Bowman's capsule; forms glomerulus; exits as efferent arteriole.
  • Peritubular capillary network: Supports nephron reabsorption and secretion.

Filtration and Osmolarity

  • Filtration: Driven by arterial pressure.
  • Osmolarity: Changes through nephron:
    • Initial filtrate (Proximal Tubule): ~300 mOsm/L
    • Bottom of Loop of Henle: ~1200 mOsm/L (water loss)
    • Distal Tubule: ~100 mOsm/L (ion reabsorption)
    • Final Urine: ~1200 mOsm/L (concentrated due to countercurrent mechanism)

Hormonal Effects and Diuretics

Hormones

  • Aldosterone: Increases sodium reabsorption (Distal Tubule, Collecting Duct).
  • Antidiuretic Hormone (ADH): Increases water reabsorption (Collecting Duct).

Diuretics

  • Types:
    • Carbonic Anhydrase Inhibitors: Affect proximal tubule.
    • Loop Diuretics: Target ascending loop of Henle (e.g., Lasix).
    • Thiazides: Affect proximal convoluted tubule.
    • Potassium Sparing Diuretics: Affect collecting duct (e.g., Spironolactone).

Reabsorption and Secretion Mechanisms

  • Sodium Importance: Major role in tubular reabsorption.
  • Symporters and Antiports:
    • Examples: Sodium-glucose symport, sodium-proton antiport.
  • pH Balance: Bicarbonate conservation and proton excretion.

Hormonal Regulation

Antidiuretic Hormone (ADH)

  • Triggered by osmoreceptors in the hypothalamus.
  • Increases cyclic AMP, inserting aquaporins in membranes.

Aldosterone

  • Produced in response to renin-angiotensin system activation (juxtaglomerular apparatus).
  • Increases sodium (and indirectly water) reabsorption.

Renal Function Indicators

Renal Clearance

  • Markers: Creatinine (endogenous marker) for GFR estimation.

Glomerular Filtration Rate (GFR)

  • Estimation: Use creatinine levels; Cockroft-Gault formula considers age, weight, gender.

Additional Tests

  • FENA: Fractional Excretion of Sodium; useful for acute renal failure assessment.
  • Other Indicators: Blood Urea Nitrogen (BUN), electrolytes, urine volume.

Summary

  • Introduction to renal physiology
  • Foundation for future discussions on kidney-related diseases.