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.