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Year 2 > Renal Week 1 > Flashcards

Renal Week 1 Flashcards

1
Q

Describe the anatomy of the kidney:

A
  • retroperitoneal organ on the posterior abdominal wall
  • LH kidney slightly higher than RHS due to absence of liver
  • superior pole at level of 11/12th ribs
  • inferior pole found 1cm above iliac crest level
  • moves 2/3cm vertically during respiration
  • cortex, medulla, renal papilla, minor calyx, major calyx, renal pelvis, hilum
  • COVERINGS: renal capsule, perirenal fat, renal fascia (Gerota’s fascia), pararenal fat
  • LYMPH: drained by lateral aortic nodes at level of renal arteries
  • BLOOD: renal arteries branch off aorta at level L1/2
  • right renal artery longer than left
  • renal veins drain into IVC, L vein longer than R vein
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2
Q

What is the renal sinus?

A

Renal pelvis + minor calyces + major calyces + nerves and vessels

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3
Q

Describe the branching system of the renal artery:

A

renal artery -> interlobular artery -> arcuate artery -> afferent arteriole -> efferent arteriole -> vasa recta

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4
Q

Describe the anatomy of the nephron:

A
  • 80% of nephrons are cortical and 20% are juxtamedullary
  • tubule of nephron lined by single layer of epithelial cells
  • common BM in bowman’s capsule between the glomerular artery epithelium and bowman’s capsule
  • endothelium of glomerular capillaries is fenestrated and covered in a -ve charged glycoprotein called podocalyxin, also covered by podocyte cells with cytoplasmic extensions called pedicles which are vital for filtration
  • mesangial cells found between loops of glomerular capillaries and they contract/relax allowing the artery diameter to be altered
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5
Q

Describe the epithelium and physiology at the PCT:

A
  • simple cuboidal epithelium
  • many mitochondria for ATP pumps
  • ~14mm long
  • 100% glucose and amino acids reabsorbed by facilitated diffusion
  • 90% bicarbonate
  • 70% NaCl and water
  • some K
  • urea secreted into tubule
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6
Q

Describe the epithelium and physiology at the thin descending LOH:

A
  • simple SQUAMOUS epithelium
  • few mitochondria and no active transport
  • the longer the LOH the more concentrated the urine can become
  • permeable to water
  • 25% NaCl and water reabsorbed
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7
Q

Describe the epithelium and physiology at the thick ascending LOH:

A
  • simple cuboidal epithelium
  • insoluble to water
  • active transport of solutes out of tubule into interstitium increases the solute concentration of interstitial fluid
  • NKCC2 pump brings Na, K and 2 x Cl into tubule so Na can be removed again by ATP pump
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8
Q

Describe the epithelium and physiology at the DCT:

A
  • simple cuboidal epithelium
  • 5% NaCl and H2O reabsorption
  • many mitochondria and ATP pumps
  • NCC channel brings Na and 2 x Cl into the tubule to be removed again by ATP pump
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9
Q

Describe the epithelium and physiology at the collecting tubules:

A
  • simple cuboidal epithelium
  • ENaC channel (epithelial sodium channel) allows Na to enter the tubule so it can be removed again by ATP pump
  • ALDOSTERONE binds to corticosteroid receptors here causing upregulation of ENaC channels
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10
Q

Describe the epithelium and physiology at the collecting duct:

A
  • simple cuboidal epithelium
  • ~1mm long
  • 2 cell types:
  • > principle cells = pale cytoplasm, short microvilli, reabsorb Na/H2O and secrete K
  • > intercalated cells = dark cytoplasm, many mitochondria, secrete H and reabsorb HCO3, important in acid base balance
  • ADH acts here causing insertion of AQP channels on basolateral membrane and allowing H2O to diffuse out and concentrate the urine
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11
Q

Describe the counter-current multiplier mechanism:

A
  • uses energy to create an osmotic gradient allowing H2O reabsorption from tubular fluid and for concentrated urine to be produced
  • NaCl is actively transported out of the thick ascending limb by NKCC2 pump. This limb is impermeable to water.
  • the Na and Cl and other ions gather in the interstitial fluid which becomes hyperosmotic
  • fluid then moves down the descending LOH and out into the interstitium down a concentration gradient. The thin descending LOH is permeable to water.
  • As fluid is constantly entering the nephron, the fluid gets pushed down the descending LOH and becomes more concentrated further down the loop
  • the longer the loop the more concentrated urine can be produced
  • the blood flow through the vasa recta is in the opposite direction so as not to wash away the gradient
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12
Q

Which side is the apical membrane?

A

Faces the lumen

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13
Q

Which side is the basolateral membrane?

A

Faces the blood / interstitium

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14
Q

Describe the anatomy and function of the juxtaglomerular apparatus:

A
  • is a specialisation of the afferent arteriole and the DCT
  • macula densa = group of cells in the DCT that are sensitive to tubular fluid content or Na
  • cluster of juxtaglomerular cells around the afferent arteriole around the afferent arteriole that contain renin granules in their cytoplasm and these cells act as baroreceptors (i.e. mechanoreceptors)

-> macula densa senses low Na content of fluid and low BP detected by JGA
-> renin is released into plasma
-> renin converts angiotensinogen (made in the liver) into AT1
-> ACE (made in lungs) converts AT1 into AT2
AT2 HAS TWO EFFECTS:
-> increases aldosterone production by the adrenals which increases Na and H2O reabsorption in the DCT
-> causes vasoconstriction

  • end result = BP increases
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15
Q

What are the functions of the kidney?

A 
RED-U-FAR
R - reabsorption
E - erythropoietin production
D - vitamin D activation
U - urine production
F - filtration
A - acid-base balance
R - renin production
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16
Q

What is GFR and how is it measured?

A
  • glomerular filtration rate
  • measure of kidney function
  • measured using an exogenous substance that is either completely filtered, completely reabsorbed
  • exogenous substances that can be measured: isohexol, radiolabelled EDTA, inulin
  • endogenous substances that can be used: creatinine and cysteine C
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17
Q

What is the relationship between GFR and creatinine?

A

As GFR decreases, serum creatinine increases

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18
Q

How can you calculate eGFR mathematically?

A

MDRD equation that takes into account

  • gender
  • race
  • age
  • result given as ml/min/1.73m2 (takes into account body surface area)
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19
Q

What are normal GFR results?

A

> or = to 60

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20
Q

What are normal eGFR results?

A

> or = to 90

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21
Q

What are the cut-offs of eGFR for kidney disease?

A

Stage 1 - >= 90 normal
Stage 2 - 60-89 = slight decrease in GFR
Stage 3A - 45-59 = moderate kidney disease
Stage 3B - 30-44 = moderate kidney disease
Stage 4 - 15-29 = severe kidney disease
Stage 5 - <15 = established renal failure

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22
Q

What are the 4 different types of kidney stones?

A

1) calcium containing e.g. calcium oxalate/calcium phosphate
2) struvite stones e.g. ammonium/Mg/PO4 conglomerates
3) uric acid stones e.g. uric acid is produced as a waste product when food containing purine nucleotides is broken down
4) cysteine stones e.g. due to rare inherited disorder called cysteinuria where you get high concentrations of the amino acid ‘cysteine’ in the urine

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23
Q

How do kidney stones arise?

A

Various factors all lead to a stone formation:

  • high Ca
  • hyperuricaemia
  • cysteinuria
  • hyperoxaluria
  • hypocitraturia
  • XS solute in renal tubules causes stones and crystals to form
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24
Q

What are the risk factors for kidney stones?

A
  • male
  • genetics
  • FH
  • BMI >27
  • UTI
  • dehydration
  • high salt and protein intake
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25
Q

What factors are protective against kidney stone formation?

A
  • high citrate and high vitamin D
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26
Q

What are signs and symptoms of kidney stones?

A
  • nausea
  • obesity
  • renal colic (secondary pain as the bladder/ureter/area of blockage tries to remove the obstruction in the collecting duct system)
  • sweating
  • hypotension
  • testicular pain
  • increased urinary frequency
  • burning sensation when urinating
  • pain in back/abdomen
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27
Q

How can kidney stones be treated?

A
  • PREVENT by intake of >2L fluid per day and healthy diet
  • low oxalate diet (less chocolate, nuts) and limit intake of high urate foods (liver, kidney)
  • stones may pass themselves by drinking plenty water and prescribing analgesics
  • give antibiotics to treat any UTI present
  • alpha-blocker if stone is stuck in ureter for smooth muscle relaxation
  • INTERVENTION
  • stent/catheter to drain blocked up urine
  • lithotripy = US waves to break up the stone
  • ureteroscopy = using an ureteroscope which is passed through the urethra and bladder to examine the ureter
  • nephrostomy - creating an artificial opening between the skin and kidney to drain urine from the renal pelvis
  • nephrolithotomy = minimally invasive, remove kidney stones through small puncture wound through skin
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28
Q

What are the commitments of being a kidney donor and what are the types of donor?

A
  • you must volunteer and can change your mind at any time right up to surgery
  • non-directed = you do not know the recipient (anonymous donation)
  • paired donation: a recipient and donor do not match HLA type and so swap with another pair
  • pooled donation: more than two pairs involved
  • in Scotland you have to be 16yrs to be legally considered as a donor, there is no maximum age limit
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29
Q

What are the ethics/considerations around kidney donation?

A
  • donor only has one remaining kidney and may affect their mental and emotional well-being
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30
Q

What % of body weight is water and how much of this is intra/extracellular?

A
  • 60% body weight is water (40% intracellular and 20% extracellular)
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31
Q

What are the forces/pressures that control fluid movement?

A
  • osmotic pressure draws fluid into a cell (works at the venous end of a capillary)
  • hydrostatic pressure pulls fluid out of cells (works at the arterial end of a capillary)
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32
Q

What is the main cation:

a) intracellularly?
b) extracellularly?

A

a) K

b) Na

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33
Q

What is the main anion:

a) intracellularly?
b) extracellularly?

A

a) PO4 and proteins

b) Cl

34
Q

If the concentration of fluid in intra/extracellular compartments is equal at 300mosm/kg, what happens if you add 1L water?

A

Water is equally distributed but the volume of all compartments increases slightly and this reduces the concentration in all the compartments to 290mosm/kg

35
Q

If the concentration of fluid in intra/extracellular compartments is equal at 300mosm/kg, what happens if you add 300meq Na?

A

NO INTRACELLULAR PARTICLES STAYS THE SAME
the number of extracellular particles increases, water distribution in the compartments changes and osmolarity becomes 307mosm/kg

36
Q

If the concentration of fluid in intra/extracellular compartments is equal at 300mosm/kg, what happens if you add 1L water and 300meq Na?

A

NO INTRACELLULAR COMPARTMENT CHANGE

  • the isotonic solution causes expansion of extracellular compartment
  • this is why in practice saline is used instead of H2O
37
Q

How are calcium levels controlled?

A
  • low Ca detected by receptor cells in the parathyroid glands
  • PTH released
  • PTH causes KIDNEYS to:
  • > increase Ca reabsorption
  • > increase PO4 secretion
  • > make hydroxylated vitamin D (so more Ca absorbed in the GI system)
  • PTH causes BONE to be broken down and:
  • > increase Ca release
  • > increase PO4 release

Normal Ca levels returned

38
Q

Describe the process of vitamin D activation:

A
  • UV light converts 7-dehydrocholesterol in the skin -> cholecalciferol (inactive vitamin D3)
  • cholecalciferol converted into 25-OH hydroxycholecalciferol in the liver by 25-hydroxylase enzyme
  • 25 hydroxycholecalciferol is then converted into 1,25 dihydroxycholecalciferol (active vitamin D3) by alpha-1-OH enzyme in the kidney
39
Q

Name a toxin that is metabolised and broken down by the kidneys:

A

Beta-2 microglobulin = produced everyday as a waste product of the inflammatory pathway

(kidneys also break down insulin and other medicines)

40
Q

How is EPO produced by the kidneys?

A
  • the hormone is excreted from the interstitial cells in the kidney
  • acts to increase RBC in response to hypoxia
  • low O2 is detected at the base of the LOH and is the trigger for EPO production
41
Q

In terms of kidney function, what is clearance?

A

Amount of fluid that is completely cleared of particles

= no. particles in urine / no. particles in plasma

42
Q

What does the plasma concentration of creatinine depend on?

A
  • muscle mass
  • kidney function
  • protein intake
43
Q

Understand how kidney function can be assessed by using creatinine and measuring GFR:

A
  • if kidneys are filtering insufficiently, plasma creatinine will be greater than urine creatinine and so GFR low
44
Q

Describe the graph showing the difference muscle mass makes to GFR:

A

page 3 week 7 lecture revision

- for same serum creatinine level, increased muscle mass will have increased GFR

45
Q

What factor cause over-estimation of eGFR?

A
  • being female
  • being elderly
  • having muscle wasting or being an amputee
46
Q

Name typical renal blood flow value:

A

At any one time the kidneys are filtering 20% of the cardiac output

47
Q

What are typical values for urine production?

A
  • with 2L intake, normal urine output = 800ml -> 2L
48
Q

What are causes of kidney disease?

A

1 - ineffective blood supply (reduced plasma volume causes narrowed arteriole)
2 - glomerular diseases (e.g. nephrititis or diabetic neuropathy)
3 - tubulo-interstitial diseases (e.g. sarcoidosis, polycystic kidney disease)
4 - obstructive uropathy (hinders normal urine flow)

49
Q

Describe the changes that occur in response to blood loss from a wound:

A
  • baroreceptors in JGA detect low blood volume and low BP
  • granular cells make renin = vasoconstriction of afferent arteriole
  • RAAS system activated
  • cells in LOH are sensitive to reduced O2 and undergo necrosis first = acute tubular necrosis may occur
  • oligouria may occur
  • as more nephrons die off, the remaining nephrons have to filter harder and they tire and die…
50
Q

What is oligouria?

A

production of abnormally small amounts of urine

51
Q

What are of the UG tract is damaged if there is protein in the urine?

A

glomeruli = suggests glomerular disease

52
Q

What are of the UG tract is damaged if there is ketones in the urine?

A

glomeruli/urinary tract

53
Q

What are of the UG tract is damaged if there is abnormal pH change of the urine?

A

tubules

54
Q

What are of the UG tract is damaged if there is glucose in the urine?

A

tubules/XS in plasma

55
Q

What are of the UG tract is damaged if there is leukocytes in the urine?

A

bladder

56
Q

What are of the UG tract is damaged if there is nitrites in the urine?

A

bladder

57
Q

What does blood in the urine suggest?

A

Glomerular disease

58
Q

What is proteinuria and how can it be quantified?

A
  • presence of XS protein in the urine

- spot protein is not quantitative and so protein:creatinine ratio can be used to assess progress of glomerular disease

59
Q

How are patients with chronic kidney disease managed?

A
  • DIALYSIS = machines acting like artificial kidneys and put small solutes through a semi-permeable membrane
  • transplant should ideally be carried out early before dialysis begins but this is not always an option
  • NICE guidelines have been established to identify adults in primary and secondary care with CKD so that it is detected and managed earlier and so has a better prognosis
60
Q

What is the relationship between CKD and CVD?

A

As a person with CKD ages, their risk of CVD increases

61
Q

Describe volatile and fixed acids in the body:

A
  • CO2 = volatile acid, as it can be eliminated from the body as a gas
  • acids from the diet/produced from metabolism and anaerobic respiration are “fixed” and cannot be converted to CO2
62
Q

What is anion gap and what does it suggest?

A
  • the no. of anions and cations in the body is ALWAYS EQUAL but on measuring U and E’s there is an anion gap as the test does not measure all cations and anions
  • the difference between the major cations and anions reflects the presence of UNMEASURED IONS in the body
  • if HCO3 is reduced an additional anion must be present, but if this anion is anything other than Cl then there will be an anion gap
  • anion gap can be classified as high or low
  • AG is used to identify the cause of metabolic acidosis (e.g. due to lactic acid build up or the ingestion of an acid/drug)
63
Q

How does lactic acidosis arise?

A
  • due to glycolytic metabolism of pyruvate
  • lactic acid normally is buffered by HCO3 to lactate and then metabolised in the liver/kidney
  • acidosis may occur if there is hypoperfusion or reduced hepatic disease
64
Q

What is osmolarity?

A

concentration of osmole per unit VOLUME (litres)

65
Q

What is osmolality?

A

concentration of osmole per unit MASS (kg)

66
Q

What is HUS?

A
  • haemolytic uraemic syndrome
  • characterised by haemolytic anaemia and nephropathy
  • can cause renal failure and microthrombosis in the body
  • is an end result of endothelial cell damage causing microvascular thrombosis
67
Q

Where are Na-K ATP pumps found in the nephron?

A

PCT, thick ascending LOH and DCT

68
Q

Where are NKCC2 channels found in the nephron?

A

thick ascending LOH

69
Q

Where are aquaporin channels found in the nephron?

A

collecting duct

70
Q

Where are Na-H antiporters found in the nephron?

A

PCT

71
Q

Where are NCC channels found in the nephron?

A

DCT

72
Q

Where are ENaC channels found in the nephron?

A

collecting duct

73
Q

What disorder can occur with dysfunction of PCT transporters?

A

Fanconi’s syndrome

74
Q

What techniques can be used to image the kidney?

A

1) X-ray - good for kidney stone identification but not kidney function
2) USS - most commonly used, cheap, safe and reliable, gives info on kidney shape/size/location/stones/renal blood flow. LIVER ALWAYS APPEARS MORE ECHOBRIGHT.
3) Doppler USS - look at renal blood flow
4) CT - may be used in addition with angiography (radio-opaque contrast)
5) MRI - gives better kidney ultrastructure than CT, can use gadolinium contrast
6) Isotope scanning - radio-isotope injected as tracer and gives information about structure and perfusion
7) Intravenous urogram NOW REPLACED BY CT

75
Q

What kidney length is indicative of CKD?

A
  • kidney length less than 9cm
76
Q

What is dangerous about using contrast techniques to assess kidney function?

A

they can be nephrotoxic, but this risk is lowered by using pre-hydration techniques

77
Q

What is gouty tophi?

A
  • nodular masses of sodium crystals deposited in the kidney, a late complication of hyperuricaemia
78
Q

What is gout?

A
  • defective metabolism of uric acid, a type of arthritis where small crystals form in and around joints
79
Q

What methods are used biochemically to diagnose kidney stone?

A
  • biochemistry useful for identifying the cause of a stone

- serum uric acid, Ca and HCO3 measured

80
Q

How can the ureter be identified in surgery?

A
  • peristalsis
81
Q

What are medullary rays?

A
  • collecting ducts that drain the nephron
82
Q

What is horseshoe kidney?

A
  • a congenital disorder where a patients two kidneys are embryologically fused together to form one horseshoe shaped kidney
  • it does not commonly cause any physiological problems

Year 2 (22 decks)

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