Renal physiology Flashcards

1
Q

What are the 4 causes of metabolic acidosis with a normal anion gap?

A

Renal tubular acidosis
Diarrhoea
Ammonium chloride ingestion
Adrenal insufficiency

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2
Q

What are the 4 causes of metabolic acidosis with a raised anion gap?

A

Lactic acidosis (hypoxia, sepsis, infarction)
Ketoacidosis (DM, starvation, alcohol)
Renal failure
Poisoning (late stages aspirin OD, methanol, ethylene glycol)

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3
Q

Give 5 causes of metabolic alkalosis.

A

Vomiting
Cardiac arrest
Multi-organ failure
CF
Potassium depletion (diuretics)
Cushing’s syndrome
Conn’s syndrome

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4
Q

Give 5 causes of respiratory alkalosis.

A

Hyperventilation
PE
Pneumothorax
CNS disorders (CVA, SAH, encephalitis)
High altitude
Pregnancy
Early stages of aspirin OD

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5
Q

Give 5 causes of respiratory acidosis.

A

COPD
Life-threatening asthma
Pulmonary oedema
Respiratory depression (Opiates, BDZs)
Neuromuscular disease (GBS, muscular dystrophy)
Incorrect ventilatory settings (hypoventilation)
Obesity

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6
Q

What doe/s the anion gap represent

A

The concentration of all the unmeasured anions in the plasma.

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7
Q

How do you calculate the anion gap?

A

Na - Cl - HCO3

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8
Q

What are the causes of a high anion gap metabolic acidosis?

A

Mnemonic CAT MUD PILES:

Carbon monoxide
Alcoholic ketoacidosis
Toluene
Metformin/ Methanol
Uraemia
Diabetic Ketoacidosis
Propylene glycol
Iron/ Isoniazid
Lactic acidosis
Ethylene glycol
Salicylates

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9
Q

What are the causes of a normal anion gap metabolic acidosis?

A

Mnemonic CAGE:

Chloride excess
Acetazolomide/ Addison’s disease
GI causes (diarrhoea, vomiting, fistulae)
Extra (renal tubular acidosis)

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10
Q

A high anion gap metabolic acidosis normally occurs due to what?

A

Accumulation of organic acid or impaired excrete of H+.

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11
Q

A normal anion gap metabolic acidosis normally occurs due to what?

A

Loss of HCO3 from extracellular fluid.

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12
Q

How is lactic acidosis defined?

A

pH <7.35
AND
lactate >5

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13
Q

What happens to the anion gap in lactic acidosis?

A

It is raised

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14
Q

What is type A lactic acidosis due to?

A

Tissue hypoxia

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15
Q

What is type B lactic acidosis due to?

A

Non-hypoxic processed affecting production and elimination of lactate.

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16
Q

Give some causes of type A lactic acidosis.

A

Shock (sepsis)
LV failure
Severe anaemia
Asphyxia
Cardiac arrest
CO poisoning
Respiratory failure
Severe asthma
COPD
Regional hypoperfusion

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17
Q

Give some causes of type B lactic acidosis.

A

Renal failure
Liver failure
Sepsis (non-hypoxic sepsis)
Thiamine deficiency
Alcoholic ketoacidosis
Diabetic ketoacidosis
Cyanide poisoning
Methanol poisoning
Biguanide poisoning

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18
Q

What is the RAAS system responsible for?

A

Regulation of arterial BP
Concentration of sodium in the plasma

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19
Q

Where is renin released from?

A

Juxtaglomerular cells

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20
Q

Where are juxtaglomerular cells located?

A

Afferent arterioles of the kidney

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21
Q

Which 3 things can cause renin to be released?

A

Decreased arterial BP (reduced renal perfusion)

Decreased sodium load delivered to the DCT

Sympathetic nervous system stimulation

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22
Q

Where is angiotensinogen produced?

A

Liver

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23
Q

What 4 factors cause an increase of angiotensinogen?

A

Increased corticosteroid levels
Increased thyroid hormone levels
Increased oestrogen levels
Increased angiotensin II levels

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24
Q

What is the function of renin?

A

Cleaves the peptide bond between leucine and valine on angiotensinogen, converting it to angiotensin I.

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25
What is the overall effect of the RAAS?
Increase mean arterial BP and restore perfusion to the kidneys
26
Release of renin is inhibited by what?
Atrial natriuretic peptide (ANP)
27
When is atrial natriuretic peptide (ANP) released?
In response to the atria being stretched during periods of high blood pressure
28
Where are macula dense cells located?
DCT
29
What does angiotensin converting enzyme do?
Removes 2 c-terminals from angiotensin I to form angiotensin II.
30
Where is ACE produced?
Lungs
31
Where is angiotensin I converted to angiotensin II?
Lungs
32
What is the main bioactive product of RAAS?
Angiotensin II
33
What does angiotensin II do to vascular smooth muscle?
Constricts it (increased BP)
34
What does angiotensin II do the efferent arteriole of the glomerulus?
Constricts it (increased filtration fraction)
35
What does angiotensin II stimulate the release of?
Aldosterone ADH
36
Where is aldosterone released from?
Zona glomerulosa of the adrenal cortex
37
Were is ADH released from?
Posterior pituitary gland
38
Where is the thirst centre of the brain?
Hypothalamus
39
What exchanger does angiotensin II act on?
Na+/H+ exchanger in PCT = Na+ reabsorption and H+ secretion
40
What are the 3 effects of angiotensin II on renal measurements?
Decreased renal plasma flow Increased filtration fraction Increased GFR
41
What is the main mineralocorticoid hormone?
Aldosterone
42
What 3 things is aldosterone released in response to?
Increased angiotensin II levels Increased potassium levels Increased ACTH levels
43
What substances does aldosterone cause reabsorption of?
Reabsorption of Na+ from DCT Reabsorption of water from DCT Reabsorption of C- from DCT
44
Where is the majority of water reabsorbed in the nephron?
PCT
45
Which limb of the loop of henle is permeable to water?
Descending limb
46
Where is the majority of sodium reabsorbed in the nephron?
PCT
47
Which part of the loop of Henle reabsorbs 25% sodium?
Thick ascending limb
48
How is water reabsorbed in the PCT?
Osmosis
49
How is sodium reabsorbed in the PCT?
Active transport
50
How is sodium reabsorbed in the thick ascending limb of the loop of henle?
Active transport
51
Where is 65% (majority) of chloride reabsorbed in the nephron?
PCT
52
How is chloride reabsorbed in the PCT?
Via a symporter with Na+
53
How is chloride reabsorbed in the ascending loop of henle?
Diffusion (in thick and think ascending LoH)
54
How is chloride reabsorbed in the DCT?
Diffusion
55
How is chloride reabsorbed in the collecting duct?
Symporter
56
Which part of the nephron are proteins reabsorbed?
PCT (almost 100%)
57
Where is 65% potassium reabsorbed in the nephron?
PCT by diffusion
58
Where is almost 100% glucose reabsorbed in the nephron?
PCT
59
How is glucose reabsorbed in the PCT?
Secondary active transport with Na+
60
What is the basic functional unit of the kidney?
Nephron
61
How many nephrons are in each kidney?
~1 million
62
In which part of the kidney does plasma undergo filtration?
Renal corpuscle (glomerulus + bowman's capsule)
63
Where does the majority of solute reabsorption occur?
PCT
64
What are the adaptations of the PCT?
Cuboidal Abundant mitochondria Brush border
65
Which part of the kidney does the loop of henle lie in?
Renal medulla
66
Which part of the loop go henle allows water to move via osmosis but does not take part in solute transport?
Descending loop of henle
67
What happens in the thick ascending loop henle?
NO water reabsorption NaK2Cl transporters absorb solutes
68
What happens in the DCT?
Fine control of urine composition
69
Where are macula dense cells?
Wall of DCT
70
Where are juxtaglomerular cells?
Wall of afferent arteriole
71
High sodium concentration in the DCT means what has happened to the GFR?
Increased (faster flow = less sodium reabsorbed)
72
What volume of plasma is filtered per minute at the glomerulus?
125ml
73
What is arterial supply to the kidneys?
Renal arteries
74
What vertebral levels do the renal arteries come off the aorta at?
L2
75
Which renal artery is longer?
Right renal artery
76
Where does the right renal artery pass in relation to the IVC?
Behind it
77
What does the right renal artery pass behind on route to the kidney?
IVC Right renal vein Head of pancreas Second part of duodenum
78
What does the left renal artery pass behind on route to the left kidney?
Left renal vein Body of pancreas Splenic vein
79
At what vertebral level do the hila of the kidneys lie?
L1 (transpyloric plane)
80
What are the 3 layers of the glomeruli filtration membrane?
Fenestrated capillary endothelium Basement membrane Filtration slits formed by foot processes of podocytes
81
What charge does the basement membrane in the glomerulus have?
Negative
82
What is the mean GFR in men and women?
130ml in men 120ml in women
83
Reabsorption in the PCT is driven by what?
ATP-dependent transporters
84
What is the main way that reabsorption occurs in the PCT?
Bulk transport (solvent drag). Means solutes are transported by the flow of water.
85
What percentage of the following substances is reabsorbed in the PCT? Glucose Amino acids Sodium Water Potassium Chloride
Glucose = 100% Amino acids = 100% Sodium = 67% Water = 65% Potassium = 65% Chloride = 65%
86
What acts as the driving force for reabsorption in the PCT?
Sodium
87
How does glucose reabsorption occur at the PCT?
Sodium-glucose co-transporters (one glucose molecule with 2 sodium molecules)
88
How are amino acids transported across the PCT?
Co-transport (Na/amino acid symporters)
89
Where does acetazolamide act?
PCT
90
What does acetazolamide inhibit?
Carbonic annhydrase
91
What is the overall effect of acetazolamide?
Reduces sodium and water resorption.
92
Where is erythropoietin produced?
PCT
93
Which cells produce erythropoietin in the PCT?
Interstitial fibroblasts
94
What percentage of sodium is reabsorbed in the loop of henle?
20-25%
95
Which part of the loop of henle is highly permeable to water?
Thin descending limb
96
What is reabsorbed in the descending limb of the loop of henle?
Water (aquaporin 1 channels)
97
What is reabsorbed in the thin ascending limb of the loop of henle?
Ions - sodium, chloride, urea NO water
98
How does ion reabsorption occur in the thin ascending loop of henle?
Paracellularly
99
What is reabsorbed in the thick ascending limb of the loop of henle?
Ions - sodium, chloride, potassium NO water
100
Why does the interstitial around the loop of henle become concentrated with ions as the fluid descends?
Counter current mechanism creates an osmotic gradient
101
Which type of diuretics act on the loop of henle?
Loop diuretics
102
How do loop diuretics act?
Inhibit NaK2Cl transporter = urine less concentrated.
103
What percentage of water is reabsorbed in the DCT?
10-15%
104
What are the 2 sections of the DCT?
Early DCT (1) Late DCT (2)
105
Where does the DCT start?
Just after the macula dense.
106
Sodium reabsorption is driven by which proteins in the primary DCT?
Na+/K+ ATPase
107
How does the movement of sodium ions occurs in the late DCT?
ENAC (epithelial sodium channel)
108
What do intercalated cells do in the DCT?
Assist with the acid-base balance
109
Which diuretics act on the DCT?
Thiazide diuretics Aldosterone antagonists
110
Where do thiazide diuretics work?
DCT
111
What do thiazide diuretics inhibit?
NaCl co-transportters (reduce sodium and water reabsorption)
112
Where do aldosterone antagonists work?
DCT
113
What do aldosterone antagonists do?
Inhibit aldosterone.