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Pathology ICSM COPY > Chemical Pathology 14 - Acute and Chronic Renal failure 1 & 2 > Flashcards

Chemical Pathology 14 - Acute and Chronic Renal failure 1 & 2 Flashcards

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1
Q

What is the best measure of kidney function?

A

GFR

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2
Q

What is a normal GFR?

A

120mls/ min

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3
Q

Define clearance and how to measure it

A

volume of plasma that can be completely cleared of a marker substance per unit time

if marker a)not bound to proteins, b)not freely filtered by glomerulus, c)not secreted or reabsorbed by tubular cells then gfr = clearnce

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4
Q

What is the gold-standard measure of GFR?

A

Inulin clearance

but required steady state infusion so reserved for research

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5
Q

What are some exogenous measure of GFR?

A

51Cr-EDTA and 99Tc-DTPA

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6
Q

How can plasma creatinine be used to estimate GFR?

A 
Clearance = P(U x V) 
P = plasma concentration 
U = urinary concentration 
V = plasma volume
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7
Q

What are some endogenous markers of GFR?

A

blood urea

creatinine

cystatin C

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8
Q

What would invalidate a creatinine-based measurement of GFR?

A

non linear creatinine:GFR relationship (↓GFR → creatinine less acurate at predicting precise GFR)

rate of creatinine generation affected by many factors

  • Muscularity (proportional to mass) - main factor
  • Age
  • Sex (higher in men)
  • Ethnicity (higher in Afro-Caribbean)
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9
Q

Why does plasma urea have a limited clinical value for measuring renal function?

A

variable resorption

dependent on nutritional state, hepatic function, GI bleeding

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10
Q

Describe the movement of creatinine from blood to urine

A

Freely filtered
Actively transported into urine by tubular cells

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11
Q

What equation can be used to refine your interpretation of creatinine clearance?

A

Cockcroft Gault Equation

  • age + weight + gender
  • May overestimate GFR (esp <30mL/min)

Estimated GFR adjusted equation / MDRD

  • age + sex + creatinine + ethnicity

CKD-Epidemiology Collaboration (CKD-EPI)

  • age + sex + creatinine + ethnicity(modelled slightly differently)
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12
Q

What is the equation for estimated creatinine clearance with the Cockroft Gault adjustment?

A

((1.23 x (140- age) x weight))/ serum creatinine
Adjust by 0.85 if female

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13
Q

What is cystatin C, and why is it particularly useful?

A

constitutively produced by all nucleated cells at a constant rate and is freely filtered

Almost completely reabsorbed and catabolised by tubular cells

Alternative to creatinine clearance
Largely unaffected by muscle mass/ gender/ age

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14
Q

In what condition does cystatin C not give a reliable result for GFR estimation?

A

Hypo/ hyperthyroidism

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15
Q

How can proteinuria be quantified?

A

Spot urine measurement

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16
Q

What can a 24-hour urine collection be used for?

A
  1. Creatinine clearance estimation
  2. Examination for stone-forming elements
  3. Proteinuria quantification (but this can also be done on spot urine testing)
  4. Electrolyte estimation (but this can also be done on spot urine testing)
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17
Q

CAn you reliably exclude bacteraemia if leucocyte esterase and nitrie is negative?

A

Yes - leucocyte esterase

No - nitrites

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18
Q

What is the preferred method for assessing urine protein creatinine ratio?

A

spot urine measurement > 24 collection

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19
Q

What does this urine microscopy show?

A

calcium oxalate crystals

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20
Q

What does this urine microscopy show?

A

RBCs - malignancy/infection

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21
Q

What does this urine microscopy show?

A

casts - fuzzy burritos (glomeraular dysfunction)

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22
Q

What does this urine microscopy show?

A

WBCs - multi nucleate cells

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23
Q

What does this urine microscopy show?

A

bacteria

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24
Q

What is the first choice of imaging in a suspected renal stone?

Study These Flashcards
A

CT KUB

2nd - USS KUB (AKI/hydronephrosis)

25
What is the first choice of imaging to assess renal blood flow?
USS with doppler
26
What is the first choice of imaging in investigating renal structural abnormalities?
CT
27
what does this show?
staghorn calculi
28
how would you differentiate between different stone types on plain KUB?
uric acid stones (no Ca) are radio lucent cystine stones present but not as dense as calcium ca stone radioopaque
29
What options are available for functional imaging of the kidney?
Static and dynamic renograms
30
What do urine calcium oxalate crystals indicate?
ethylene glycol poisoning (anti-freeze) Ethylene glycol metabolises to form calcium oxalate crystals symptoms of alcohol intoxication?
31
Recall the increases in creatinine that define each stage of AKI
Stage 1: 1.5-1.9 x the reference (≥26 μmol/L) Stage 2: 2-2.9 x the reference Stage 3: \>=3 x the reference (or \>354) Or UO \< 0.5 ml/kg/hr
32
Systematically recall some differentials for pre-renal AKI
reduced renal perfusion pressure WITHOUT structural abnormality Water loss: diuresis/ vomiting Selective ischaemia: renal artery stenosis Blood loss: road traffic accident/ drugs affecting renal blood flow Oedematous states: heart failure/ liver failure Hypotension
33
Recall 5 drug classes that can predispose to pre-renal AKI and the mechanism of each of these
NSAIDs - decrease afferent arteriolar dilatation Calcineurin inhibitors - decrease afferent arteriolar dilatation ACE inhibitors: decrease efferent constriction ARBs: decrease efferent constriction Diuretics: affect tubular function and pre-load
34
what is the normal response to reduced circulation volume?
activation central baroreceptors activation of RAAS, release of vasopressin and activation of SNS vasoconstriction, ↑CO and renal sodium retention AKI when these mechanisms fail
35
What is the relationship between pre-renal AKI vs acute tubular necrosis?
pre-renal AKI - no structural damage but prolonged insult → ischaemic injury → ATN ATN does not respond to restoration of blood voume
36
what would you see on urine microscopy in ATN?
epithelial cell casts
37
Systematically recall some causes of intrinsic renal AKI
Vascular causes (vasculitis/ vasculitides) Glomerular (glomerulonephritis) **Tubular (ATN) -most common** Interstitial (analgesic nephropathy)
38
What is the most common cause of intrinsic renal AKI?
Acute tubular necrosis
39
What are some common mechanisms of renal injury?
**_direct tubular injury_** * ichaemic - most common * toxins (myoglobin,immunoglobulins, aminoglycosides, amphotericin, acyclovir) **_immune dysfunction_** * glomerulonephritis * vasculitis (40y/o, systemic purpura and AKI) **_infiltration/abnormal protein deposition_** * amyloidosis * lymphoma * myeloma related renal disease
40
Recall 3 differentials for the causes of post-renal AKI
intra-renal obstruction ureteric obstruction (bilat) prostatic/urethral obstruction blocked urinary catheter
41
what is this ultrasound showing?
hydronephrosis commonly secondary to BPH
42
What are the 2 best measures of AKI severity?
Creatinine Urine output
43
What endocrine hormone is made in the kidneys?
1a hydroxylase in kidneys – sarcoid macrophages express this → sarcoidosis hypercalcaemia
44
How is CKD stage 1-5 defined?
Kidney damage with normal GFR (\>90)
45
What is the best measure of prognosis in CKD?
Albumin creatinine ratio
46
What are common causes of CKD?
**Diabetes by a long mile** * hypertension (atherosclerotic renal disease) * chornic glomerlonephritis * infective or obstructive uropathy * PCKD
47
How can CKD cause a failure of homeostatsis?
1. Renal metabolic acidodis - ↓ H+ excretion 2. Hyperkalaemia - ↓ K+ excretion (DIET intake is major cause)
48
what medications can cause hyperkalaemia?
ACEi spironolactone potassium sparing diuretics
49
what ECG changes do you see in hyperkalaemia?
tall peaked t waves -\> eventually ventricular tachy
50
How can CKD cause a failure of hormonal function?
1. AOCD - normochromic normacytic anaemia due to failure of EPO production 2. renal bone disease - secondary hyperparathyroidism due to low vit D)
51
How can end-stage CKD affect the heart?
vascular calcification - renal vascular lesions - heavily calcified plaques instead of lipid atheromas uraemic cardiomyopathy - LV hypertrophy, dilatation, dysfunction CKD --\> less PTH action --\> calcium elevated --\> cardiac myocyte dysfunction --\>
52
What are some renal bone diseases that can occur as a result of CKD?
osteitis fibrosa * osteoclastic resorption of calcified bone and replacement by fibrous tissue * feature of hyperparathyroidism osteomalacia * insufficient mineralisation of bone osteoid bc body is trying to mobilise calcium from bone adynamic bone disease * excessive suppression of PTH (from overtreatment) → low turnover and reduced osteoid
53
How should renal bone disease be treated (3 ways)?
1. Phosphate control (phosphate binding drugs) 2. Vitamin D receptor activators (eg 1 alpha calcidol, paricalcitol) 3. PTH suppression (cinacalcet - ↑ Ca sensing R)
54
How would you treat renal AOCD?
artificial erythropoeisis stomulating agents (ESAs) Erythropoietin alfa (Eprex) Erythropoietin beta (NeoRecormon) Darbopoietin (Aranesp)
55
How would you treat renal acidosis
oral sodium bicarbonate
56
What are some indications for renal dialysis?
AEIOU 1. Acidosis 2. Electrolyte (refractory hyperkalaemia) 3. Intoxication 4. Oedema (refractory fluid overload) 5. Uremic symptoms (encephalopathy, nausea, pruiritis, malaise, pericarditis)
57
What is the likely diagnosis of new onset AKI when someone presents with dark urine and bruising?
rhabdomyolysis
58
systemic vasculitis
59
Name a contraindication for dialysis
active sepsis

Pathology ICSM COPY (90 decks)

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