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CLIX > Renal Function Tests > Flashcards

Renal Function Tests Flashcards

1
Q

How much urea is excreted daily?

A

250-580mmol/day

-amount depends on diet (esp. protein)

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2
Q

How much creatinine is excreted daily in urine?

A

10mmol/day

-always the same

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3
Q

What are the normal renal functions?

A
  1. urine formation
  2. acid:base balance
  3. electrolyte balance
  4. endocrine function –> EPO production
  5. hydrolation of vitamin D to active form
  6. maintenance of stable BP –> RAAS + ADH
  7. maintenance of normal plasma osmolarity
  8. gluconeogenesis
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4
Q

What is the normal plasma osmolarity and how is it calculated?

A

275-295mmol/L

2xNa + glucose + urea = P osmolarity

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5
Q

What triggers renin activation?

A

low sodium content in filtrate

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6
Q

What is the function of renin?

A
  • converts angiotensinogen –> angiotensin 1

- vasodilation of afferent arteriole of glomerulus

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7
Q

True or False?

Angiotensin II vasodilates glomerular afferent arteriole

A

False

  • powerful vasoconstrictor
  • constricts glomerular afferent arteriole
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8
Q

Where does Angiotensin II act in the kidney and what does this cause?

A

-promotes sodium and water retention by the kidney by acting on the proximal convoluted tubule

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9
Q

What stimulates aldosterone production?

A

hyperkalemia and angiotensin II

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10
Q

What part of the nephron does aldosterone act on?

A

promotes sodium and water reabsorption at the distal nephron

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11
Q

What part of the nephron does ADH act on?

A

promotes water reabsorption in the collecting ducts

-in the absence of ADH the CD are impermeable to water

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12
Q

What stimulates ADH secretion?

A

-increased plasma osmolarity (hypernatremia)

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13
Q

As GFR decreases what happens to blood urea?

A

increases

-as kidneys are the only source of urea excretion

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14
Q

What is normal GFR?

A

> 90ml/min (180L filtrate per day)

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15
Q

What GFR is diagnostic of end stage renal failure?

A

<15ml/min (stage 5) –> need dialysis

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16
Q

What does FENa reflect?

A

% of filtered sodium that is excreted in the urine

  • <1% = normal/pre-renal failure
  • > 2% = intrinsic renal failure –> as tubular damage prevents sodium reabsorption
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17
Q

What happens to the UCR in pre-renal, intrinsic and post-renal failure?

A

pre-renal –> increases
intrinsic –> decreases
post-renal –> increases

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18
Q

What is the normal amount of daily proteinuria?

A
  • tiny amount of albumin (<30mg/day)
  • Tamm-Horsfall Protein (not filtered - it is produced in the tubules)

**total = 150mg/day –> not detected on urine dipstick (not sensitive enough)

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19
Q

What is the first sign of diabetic nephropathy/kidney damage?

A

microalbuminurea (30-300mg/day)

-detected only by special or lab. dipstick

20
Q

What is macroalbuminuria?

A

-indicates overall kidney function and can be detected on normal dipstick (>/= 300mg/day) –> ACR over 30

21
Q

What is the normal ACR?

A

0-3 (0-30mg albumin/day)

22
Q

What is urine specific gravity?

A

-reflects the mass of 1ml of urine compared with 1ml of distilled water (normal = 1.001 - 1.035)

23
Q

What are causes of increased urine osmolarity?

A
  • SIADH
  • dehydration
  • glycosuria
  • adrenal insufficiency
  • high protein diet
24
Q

What are causes of decreased urine osmolarity?

A
  • diabetes insipidus
  • excessive hydration (oral or IV)
  • acute renal insufficiency
25
Q

What are the causes of pre-renal failure?

A
  • ineffective circulation
  • poor perfusion + decr. GFR
  • LV failure (decr. CO)
  • decr. circulating blood volume (haemorrhage, dehydration)
  • sepsis, liver failure, renal artery obst., renal vein thrombosis
26
Q

What are the causes of intrinsic renal failure?

A
  • glomerular lesions (e.g. glomerulonephritis)
  • tubular lesions (e.g. ischaemia)
  • interstitial lesions (e.g. pyelonephritis)
  • vascular lesions (e.g. vasculitis)
27
Q

What are the causes of post-renal failure?

A

-obstruction (urethral stricture - caliculi, BPH, bladder ca., renal artery obst.)

28
Q

When would you see hyaline casts in urine?

A
  • seen in normal urine

- may be increased numbers in dehydration

29
Q

When would you see muddy brown casts?

A

acute tubular necrosis

30
Q

When would you see broad waxy casts?

A

CKD

31
Q

What is the cardinal feature of CKD?

A

nocturia

32
Q

What are the 3 main etiologies of CKD?

A
  1. diabetes mellitus
  2. HTN
  3. chronic glomerulonephritis
33
Q

When would you see red cell casts?

A

glomerulonephritis

34
Q

What are the 3 main features of nephrotic syndrome?

A
  1. massive proteinuria (>3.5g/day)
  2. hypoalbuminemia
  3. oedema
35
Q

True or False?

pts. with nephrotic syndrome will have hyperlipidaemia

A

True

-increased total cholesterol + LDL

36
Q

Why are pts. with nephrotic syndrome prone to infections?

A

loss of Ig in urine

37
Q

What is the pathogenesis of hypercoagulability in nephrotic syndrome?

A
  • urinary losses of anticoagulants

- increased liver synthesis of procoagulants stimulated by hypoalbuminemia

38
Q

What stain is used to determine IgA nephropathy?

A

IgA immunofluorescence stain

39
Q

What will happen to plasma and urine osmolarity in SIADH?

A

P osmolarity –> low

U osmolarity –> high

40
Q

What is anemia of renal disease?

A

When kidneys are diseased or damaged, they do not make enough erythropoietin (EPO). As a result, the bone marrow makes fewer red blood cells, causing anemia

41
Q

What happens to sodium levels in kidney failure?

A
  • often normal as although less sodium is filtered due to fall in GFR, less is also reabsorbe back into the bloodstream
  • filtration:reabsorption both proportionally decreased
42
Q

What happens to potassium levels in kidney failure?

A
  • elevated
  • it is not able to be excreted in sufficient amounts in the urine
  • also increases due to acidosis
43
Q

What happens to bicarbonate levels in kidney failure?

A
  • decreased

- when acidosis develops, bicarb falls as it is used in buffering the excess H+

44
Q

What happens to calcium levels in kidney failure?

A
  • initially decreases due to insufficient hydroxylation of vit. D by kidneys
  • when secondary hyperparathyroidism develops, calcium levels normalise
45
Q

What happens to phosphate levels in kidney failure?

A
  • elevated
  • not able to be excreted in sufficient amounts in the urine and rises due to secondary hyperparathyroidism + acidosis leading to osteoclastic activity

CLIX (4 decks)

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