Renal Physiology and Diuretics

Question 1

Describe the glomerulus of the kidney?

Answer 1

• Epithelial pouch invaginated by capillary tuft
• Semi-permeable filter
  
  • Endothelium
  • BM
  • Epithelium
• Mesangial cells are specialised smooth muscle cells that support the glomerulus and regulate blood flow/GFR

Question 2

Describe the relevance of Na+ reabsorption?

Answer 2

• Main factor for determining extracellular volume
• Reduced BP and NaCl at macula densa (DCT)
  
  1. Renin release
  2. Aldosterone release
  3. More Na/K pumps

Question 3

Describe the relevance of water reabsorption?

Answer 3

• Determines extracellular fluid osmolality
• Raised osmolality / hypotension
  
  • => ADH release

Question 4

Describe the PCT of the nephron?

Answer 4

• Reabsorption of filtrate
  
  • 70% of total Na+ reabsorption
  • Reabsorption of amino acids, glucose, cations
  • Bicarbonate reabosrbed using carbonic anhydrase

Question 5

Describe the Thick ascending limb of the nephron?

Answer 5

• Creation of osmolality gradient
  
  • 20% of Na reabsorption
  • Na/K/2Cl triple symporter

Question 6

Describe the DCT of the nephron?

Answer 6

• pH and Ca2+ reabsorption
  
  • 5% of Na reabsorption
  • Apical NaCl co-transporter
  • Ca2+ reabsorption under control of PTH

Question 7

Describe the medullar collecting duct of the nephron?

Answer 7

• pH and K+ regulation
  
  • Na+ reabsorption coupled to K or H excretion
  • Basolateral aldosterone-sensitive Na/K pump

Question 8

Describe the cortical collecting duct of the nephron?

Answer 8

• Regulation of water reabsorption
  
  • Controled by aquaporin-2 channels

Question 9

Describe the endocrine function of the kidney?

Answer 9

• Secretion of renin by juxtaglomerular apparatus
• EPO synthesis
• 1a-hydroxylation of vitamin D (controlled by PTH)

Question 10

MOA of Carbonic anhydrase inhibitors?

Answer 10

• Inhibit carbonic anhydrase in the PCT
• Reduced bicarbonate reabsorption
  
  • Causes small increase in Na+ excretion

Question 11

Example of a Carbonic anhydrase inhibitor?

Answer 11

Acetazolamide

Question 12

Indication for Carbonic anhydrase inhibitor?

Answer 12

Glaucoma

Question 13

SEs of Carbonic anhydrase inhibitor?

Answer 13

• Drowsiness
• Renal stones
• Metabolic acidosis

Question 14

MOA of loop diuretics?

Answer 14

• Inhibit Na/K/2Cl symporter in thick ascending limb
• Massive NaCl excretion
  
  • • Ca2+ and K+ excretion

Question 15

Examples of loop diuretics?

Answer 15

• Furosemide
• Bumetanide

Question 16

Indications for loop diuretics?

Answer 16

• Treatment of oedema
  
  • CCF
  • Nephrotic syndrome
  • Hypercalcaemia

Question 17

SEs of loop diuretics?

Answer 17

• Hypoakalaemic metabolic alkalosis
• Hypovolaemia

Question 18

MOA of thiazide diuretics?

Answer 18

• Inhibit NaCl co-transporters in DCT
• Moderate NaCl excretion
• Increased calcium reabsorption

Question 19

Example of thiazide diuretics?

Answer 19

Bendroflumethiazide

Question 20

Indication for thiazide diuretics?

Answer 20

• HTN
• Reduce renal stones
• Mild oedema

Question 21

SEs of thiazide diuretics?

Answer 21

• Hypokalaemia
• Hyperglcyaemia
• Increased urate (contraindicated in gout)

Question 22

MOA of K+-sparing diuretics?

Answer 22

• Spiro: aldosterone antagonist
• Amiloride: blocks DCT/collecting duct luminal Na+ channel
• Increased Na+ excretion, erduced K+ and H+ excretion

Question 23

Examples of K+-sparing diuretics?

Answer 23

• Spironolactone
• Epelerone
• Amiloride

Question 24

Indications for K+-sparing diuretics?

Answer 24

• Used with loop/thiazide diuretics to control K+ loss
• Spironolactone has long term benefits in aldosteronism

Question 25

SEs of K+-sparing diuretics?

Answer 25

• Hyperkalaemia
• Anti-androgenic (Eg gynaecomastia)

Question 26

MOA of osmotic diuretics?

Answer 26

• Freely filtered and poorly reabsorbed
• Reduced brain volume and ICP

Question 27

Example of an osmotic diuretic?

Answer 27

Mannitol

Question 28

Indications for mannitol?

Answer 28

• Glaucoma
• Raised ICP
• Rhabdomyolysis

Question 29

Side effects of osmotic diuretics?

Answer 29

• Hyponatraemia
• Pulmonary oedema
• N/V