(SDL) Renal function and hydration status Flashcards
1
Q
What is in a steady state during health?
A
Intake + metabolic production = body volume = excretion
2
Q
The concentration of any solute eg. urea/Na depends on what?
A
The amount of the solute present and the volume of solvent (water) in which it is dispersed
3
Q
What are the functions of the kidney?
A
- excretion eg. urea, uric acid
- regulation eg. homeostasis, water, acid base
- endocrine eg. renin, erythropoietin, 1,25-dihydroxycholecalciferol
4
Q
What are the purposes of renal function tests?
A
- detect renal damage
- monitor functional damage
- distinguish between impairment and failure
5
Q
Imagining the kidney is like a filter, what are the inputs and outputs?
A
Input = arterial Output = venous + urine
6
Q
How do you know the kidney isn’t functioning?
A
- no urine
- clinical symptoms
- tests
7
Q
Give examples of causes of kidney failure?
A
- pre-renal eg. decreased ECFV or MI
- renal eg. acute tubular necrosis
- post-renal eg. ureteral obstruction
8
Q
What does ECFV stand for?
A
Extracellular fluid volume
9
Q
What are the laboratory tests for renal function?
A
- GFR/eGFR (estimate)
- creatinine clearance
- plasma creatinine
- plasma urea
- urine volume
- urine urea/sodium/protein/glucose
- haematuria
10
Q
What do you look for in the urine in renal function tests?
A
- volume
- urea
- sodium
- protein
- glucose
- blood
11
Q
What is the normal urine volume in health?
A
750-2000 ml/24hr
12
Q
What urine volume defines oliguria?
A
13
Q
What urine volume defines anuria?
A
14
Q
What urine volume defines polyuria?
A
> 3000 ml/24hr
15
Q
Describe the usefulness of plasma urea in renal function tests?
A
- quick, simple measurement
- wide reference range (3-8mmol/L)
- sensitive but non-specific index of illness
16
Q
What are the factors that influence plasma urea concentration?
A
- GIT protein + tissue protein = liver amino acids
- kidney filtration
- kidney reabsorption excretion
- distribution volume
17
Q
Where is urea filtered?
A
At the glomerulus
18
Q
How much filtered urea is reabsorbed by renal tubules in health?
A
About 40%
19
Q
More urea is reabsorbed if what?
A
If rate of tubular flow is slow
20
Q
More urea is reabsorbed if rate of tubular flow is slow. Why might tubular flow rate be slow?
A
When there is renal hypoperfusion
21
Q
What might cause increased plasma urea?
A
- GI bleed
- trauma
- renal hypoperfusion (decreased RBF, ECFV)
- acute renal impairment
- chronic renal disease
- post-renal obstruction (calculus, tumour)
22
Q
Describe the usefulness of urea tests
A
- useful test but must be interpreted with great care
- always consider input, output and patient’s fluid volume
23
Q
What is the normal plasma creatinine levels?
A
50-140 umol/L
24
Q
When does plasma creatinine increase in concentration?
A
As GFR decreases
25
Is plasma creatinine proportional to renal damage?
No
26
What is more important about plasma creatinine than the absolute value?
Change within an individual patient
27
What happens as GFR increases?
Plasma creatinine decreases
28
What may happen to plasma creatinine in chronic renal disease?
May increase to 1000umol/L
29
A plot of reciprocal plasma creatinine against time in chronic renal disease predicts what?
When intervention is required in end stage renal failure
30
When is GFR measured?
Seldom measured in clinical practice
- kidney donors
- dose of drug
31
What is GFR?
Clearance of [99Tc]-Sn-DTPA
32
How is creatinine clearance measured?
(Ucreat x V)/Pcreat = Ccreat
33
What is the normal creatinine clearance?
100-130mL/min
34
What does Ucreat mean?
Urine creatinine concentration (mmol/L)
35
What is V?
Urine volume (mL collected in 24 hours)
36
What does Pcreat mean?
Plasma creatinine concentration (umol/L)
37
How much higher than GFR is creatinine clearance in health?
10-30% higher than GFR
38
How can tubular secretion of creatinine be altered?
- tubular secretion increased in chronic renal disease
| - tubular secretion inhibited by drugs eg. salicylate, cimetidine
39
Why is creatinine clearance an unreliable test?
- problems with incomplete collection
| - tubular secretion can be increased in chronic renal disease and inhibited by drugs
40
What plasma change occurs when creatinine clearance is 60-120ml/min?
None
41
What plasma change occurs when creatinine clearance is 30-60ml/min?
- increased creatinine
| - increased urea
42
What plasma change occurs when creatinine clearance is 20-30ml/min?
- increased potassium
| - decreased bicarbonate
43
What plasma change occurs when creatinine clearance is 10-20ml/min?
- increased phosphate
| - increased uric acid
44
What happens with creatinine clearance in progression of chronic renal disease?
Creatinine clearance decreases as chronic renal disease progresses
45
How is eGFR calculated?
Calculated by the lab using an international formula, takes into account creatinine levels
46
Is eGFR reliable?
- lots of problems when first introduced (different formulas, creatinine tests different in different places)
- now more standardised and reliable
47
What are the different GFRs for different stages of CKD?
```
stage 1 = GFR 90+
stage 2 = GFR 60-89
stage 3a = GFR 45-59
stage 3b = GFR 30-44
stage 4 = GFR 15-29
stage 5 = GFR
```
48
Being on dialysis automatically means which stage CKD?
Stage 5
49
Describe stage 1 CKD
Normal kidney function but urine findings or structural abnormalities or genetic trait but to kidney disease
50
Describe stage 2 CKD
Mildy reduced kidney function + other findings (stage 1) point to kidney disease
51
Describe stage 3 CKD
Moderately reduced kidney function
52
Describe stage 4 CKD
Severely reduced kidney function
53
Describe stage 5 CKD
Very severe, or endstage kidney failure
54
What is endstage kidney failure also sometimes called?
Established renal failure
55
What is the treatment for stage 1 CKD?
Observation, control of blood pressure
56
What is the treatment for stage 2 CKD?
Observation, control of blood pressure and risk factors
57
What is the treatment for stage 3 CKD?
Observation, control of blood pressure and risk factors
58
What is the treatment for stage 4 CKD?
Planning for end stage renal failure
59
What is the treatment for stage 5 CKD?
Treatment choices - dialysis/transplant
60
What is skin turgor?
Skin's ability to resist a change in shape and use elasticity to return to normal. Used to assess dehydration
61
What may cause pre-renal oliguria/failure?
Low renal perfusion
- dehydration (sodium/water)
- haemorrhage
- renal artery damage
- hypotension
eg. patient with oesophageal stricture, not been drinking
62
What results would you expect in pre-renal oliguria? (in dehydration)
- GFR reduced
- ADH increased (concentrated urine/low volume)
- hypo-perfusion = renin secretion (functioning nephrons increase sodium reabsorption (aldosterone) so urine sodium low)
- high plasma Na
- high plasma urea
- high plasma creat
63
What plasma values would you test for?
- Na
- urea
- creat
64
What urine values would you test for?
- Na
| - urea
65
What would you test about the urine?
- volume
- concentration
- Na and urea levels
66
What is lassitude?
State of physical or mental weariness; lack of energy
67
What may cause renal oliguria/failure?
Intrinsic damage
- tubular necrosis
- chronic infection
- immunological damage eg. SLE
- toxic damage eg. drugs, heavy metals (Hg, Ur), poisons (paraquat)
68
How might a patient with renal oliguria present?
- increasing lassitude
- shortness of breath
- swelling of ankles
- pale
- hypertensive
69
What plasma test results would you expect in renal oliguria?
- high plasma Na
- high plasma urea
- very high plasma creatinine
70
What urine test results would you expect in renal oliguria?
- urine Na higher than in pre-renal
- urine urea lower than in pre-renal
- weak urine/low volume
71
What would you expect the GFR to be in renal oliguria?
GFR reduced/normal
72
How would you expect renal oliguria to affect renal renin secretion and what are the consequences?
Renal renin secretion may be raised
- hypertension
- but nephrons unable to reabsorb sodium
- urine sodium is >40mmol/L
73
What are some other clues pointing towards renal renal failure?
- anaemia
- haematuria
- proteinuria
- urine casts
74
What are some other problems associated with renal renal failure?
- calcium/phosphate
| - bone disease
75
What are the laboratory tests for renal function?
- plasma creatinine
- plasma urea
- plasma sodium
- urine volume
- urine sodium
- urine urea
- creatinine clearance
- urine dipsticks
76
What is wrong with certain lab tests for renal function?
- GFR = impractical
- creatinine clearance = unreliable
- plasma creatinine = specific but insensitive
- plasma urea = subject to problems
- urine volume = often forgotten
77
How is oliguria differentiated between pre-renal and renal?
UNa mmol/L
PRU = 40
P/U urea ratio
PRU = >5 fold
RRF =
