The Kidney

Question 1

What processes do the kidneys regulate in homeostsis?

Answer 1

1. Acid-base balance
   * Bicarbonate levels

2.Reabsorption of fluid
* Electrolyte balance
* Na2+/K+

3.Controls BP (RAAS)
* Vol of ECF

4.Excretion of waste products
* Urea, uric acid, creatine

Question 2

Kidney stats.

Answer 2

• Kidneys recieve 25% of CO
• Renal blood flow of 1200 ml/min
• Renal plasma flow 660 ml/min
• GFR 125 ml/min

Question 3

What is the functional unit of the kidney?

Answer 3

• The nephron
• 1.3X106 in each kidney
• Form cortex of kidney
  1. Loop of Henle within medulla
• Permeability varies across the tubule
• Hormones
  1. Aldosterone
  2. ADH

Question 4

What is the kidney the important target of?

Answer 4

• Hypertension
• CV disease
• Diabetes
• Normal kidney function is vital

Question 5

What are diuretics?

Answer 5

• Drugs that increase water excretion

Question 6

What are osmotic diuretics?

Answer 6

• E.g. Mannitol
• Inc osmolarity of tubular fluid in:
  1. PCT
  2. Loop of H
• Reduce passive reabsorption of H2O
• Used to treat cerebral oedema

Question 7

What are loop diuretics?

Answer 7

• E.g. Furosemide
• Powerful diuretic ‘High ceiling’
• Cause 15-25% of filtered Na+ to be excreted
• Block Na/2Cl/K symporter
• Impair ability of loop of H to concentrate urine;
  1. By inhib creation of hyprtonic interstatium in medulla
• Important role in treating chronic heart failure
  1. Venodilator used in left ventricular failure, pulmonary oedema, renal failure

Question 8

What are Thiazide diuretics?

Answer 8

• E.g. Bendrofumethiazide;
• Inhibit active reabsorption of Na+
• Inc solute content of tubular fluid
• So, dec gradient for water reabsorption
• First line treatment for hypertension
• Linked to hypokalaemia
• Metabolic disturbances and impaired glucose control

Question 9

What is Hypokalaemia?

Answer 9

• Major adverse effect of loop diuretics and thiazides
• Inc loss of K+ ions
• Leads to hyperpolarisation
• Predisposes to cardiac arrhythmias
• Activate RAAS to release aldosterone
• Alters expression of Na+ channels

Question 10

What are K sparring diuretics?

Answer 10

• Weak diuretics
• Reduce risk of hypokalaemia

1. Na+ channel blockers
   * E.g. Amiloride
   * Block luminal Na+ channels in DCT and CD
2. Aldosterone receptor antagonists
   * E.g. Spironolactone
   * Block aldosterone receptors
   * Prevent expression of Na+ pumps and channels

Question 11

What are the two types of dialysis?

Answer 11

1. Hemodialysis
2. Peritoneal

Question 12

What is Urinary Incontinence (UI)?

Answer 12

• 10% of adult population
• Anti-muscarinic drugs target overactive bladder
• M3 receptors of bladder smooth muscle
• E.g. oxybutynin

Question 13

What are some drugs to treat UI?

Answer 13

1. Duloxetine
   * Serotonin and NA reuptake (SNRI)
2. Amitriptyline
   * Tricyclic antidepressant
   * Serotonin and NA reuptake inhibitor
3. Desmopressin
   * Synthetic analogue of vasopressin
   * Reduce urin formation in kidney