Acute And Chronic Kidney Disease Flashcards
What is AKI?
Clinical syndrome
Abrupt decline in actual GFR (days to weeks)
Upset of ECF volume, electrolytes and acid-base balance
Accumulation of nitrogenous waste products
Why is AKI difficult to diagnose?
Doesn’t present with a specific identifiable symptom
Measurements are not massively accurate either
What happens to serum creatinine as kidneys decline?
Kidney decline leads to increased serum creatinine
How do we define AKI through measurements?
Increased serum creatine > 26.5 micromoles/L within 48 hrs
Increased serum creatinine > 1.5 x their baseline in 7 days
Urine volume <0.5 ml/kg/h for 6 hours
Describe the staging of AKI
1 - 3 in increasing severity
1 = 1.5 - 2 times their baseline
2 = 2 - 3 times their baseline
3 = > 3 times their baseline
What are the types of AKI?
Pre-renal
Intrinsic renal
Post-renal
What are the causes of pre-renal AKI?
Blood supply compromised
Volume depletion
Heart failure
Cirrhosis
Give some renal causes of AKI
Renal artery/vein occlusion Glomerulonephritis Intrarenal vascular Ischaemic ATN Toxic ATN Interstitial disease Intrarenal disease Intrarenal obstruction
What does ATN stand for?
Acute tubular necrosis
What type of AKI are the vast majority?
Pre-renal
90% of intrinsic renal causes of AKI are due to …
ATN
Give some general causes of AKI
Infective Diarrhoea Obstetric illness Venoms Malaria Dyes
Describe how pre-renal problems cause AKI
Actual GFR reduced due to decreased renal blood flow
No cell drainage
Kidney works hard to restore blood flow
Increased reabsorption of salt and water (lots of aldosterone and ADH)
RAAS activated
Responds to fluid resuscitation
Describe autoregulation of the kidneys
Keeps the kidneys between a minimum and maximum BP over which they can maintain a normal perfusion pressure
When hypertensive, these values shift to higher BPs (reset)
What is the SM response to decreased renal perfusion?
Vasodilation of afferent
Vasoconstriction of efferent
Why do NSAIDs make AKI worse?
Inhibition of production of prostaglandins
Cannot vasodilate in the arterioles of kidneys when required
Cannot regulate perfusion pressure
Why can ACEi make AKI worse?
Cannot vasoconstrict when need to
Give some causes of reduced ECF volume
Hypovolaemia Blood loss Fluid loss Sepsis Cirrhosis Anaphylaxis LV dysfunction Valve disease Tamponade
Give some causes of impaired renal autoregulation
Sepsis Hypercalcaemia Hepatorenal syndrome NSAIDs ACEi AngII antagonists
What are the causes of ATN?
Ischaemia
Nephrotoxins
Sepsis
Why is ATN a misnomer?
As there is generally no tubular necrosis
But cells are damaged
Describe ATN
Damaged cells cannot reabsorbed salt and water efficiently
Or expel excess water
Aggressive fluid resuscitation risks fluid overload
Lost the ability to concentrate urine therefore urine comes out at the same rate no matter the volume of ECF
If dialysis is required, does the mortality of AKI increased or decreased?
Mortality increases
Which parts of the nephron are most susceptible to hypoxia?
S3 of PCT
Thick ascending limb LOH
Describe damage in the kidneys due to nephrotoxins
Damage the epithelial cells lining the tubules and cause cell death and shedding into the lumen
Can be endogenous or exogenous
ATN more likely if reduced perfusion and a nephrotoxin
Give examples of endogenous nephrotoxins
Myoglobin
Urate
Bilirubin
In which treatment does urate build up?
Chemotherapy
Give some examples of exogenous nephrotoxins
Bacteria endotoxins
Xray contrast
Drugs (ACEi, aminoglycosides, NSAIDs)
Poisons (weedkillers, antifreeze)
How does rhabdomylosis cause ATN?
Muscular necrosis releases myoglobin ‘crush injury’
In wars and natural disasters
Can occur in drug users and elderly when cannot move
Myoglobin is toxic to tubule cells and can also cause obstruction
Describe acute glomerulonephritis
Immune disease affecting the glomeruli
Can be primary or secondary
Give 2 types of rapidly progressing glomerulonephritis
Granulomatosis with polyangiitis
Crescenteric necrotising glomerulonephritis
Describe acute tubulo-interstitial nephritis
Caused by infection or toxins
Massive inflammatory infiltrate (lymphocytes)
What percentage of AKIs are post-renal causes?
5-10%
What is the general mechanism for post-renal AKI?
Obstruction most block both kidneys or a single functioning kidney
Rise in intraluminal pressure
Dilation of renal pelvis
Decrease in renal function
Give some causes of post-renal AKI
Within lumen - stones, clots
Within wall - strictures (eg. Post-TB)
Pressure from outside - BPH, tumour, aortic aneurysm
Describe the serum changes common to all AKIs
Increased urea
Increased creatinine
What are the ECG changes of hyperkalaemia?
Tall T waves Small/absent P waves Increased P-R interval Wide QRS Sine wave pattern Asystole
What do we check to see if the patient is volume depleted?
Cool peripheries Increased pulse Decreased BP Postural hypotension Low JVP Reduced skin turgor
What do we assess when looking for fluid overload?
Gallop rhythm Increased BP Raised JVP Pulmonary oedema Peripheral oedema
Describe the Hx of a patient will post-renal AKI
Anuria A single functioning kidney Loin/supra-pubic pain Hx of stones Hx of prostration or previous pelvic/abdo surgery
What should we examine for in post-renal AKI?
Palpable bladder
Pelvic/abdo masses
Enlarged prostate
(Blocked catheter)
What is essential to do for every patient with AKI?
Urinanalysis
Blood, protein, leukocytes
What features of a urinanalysis of AKI when suggest intrinsic renal disease?
Blood and/or protein
How do we image AKI?
Ultrasound scan - obstruction
CXR - fluid overload, infection
Name some preventative methods for AKI
Identify risk factors Monitor at risk patients Ensure adequately hydrated Avoid nephrotoxins Detect early and identify cause
Give some of the susceptibilities for AKI
Increased age CKD Heart disease Liver disease Diabetes mellitus Neurological impairment Cancer Previous AKI
Give some exposure risk factors for AKI
Dehydration/volume depletion Sepsis Critical illness Burns/trauma Cardiac surgery Emergency surgery Nephrotoxins Contrast
What is the management for AKI?
Treat fluid overload - restrict Na+ and water
Treat hyperkalaemia with calcium gluconate, restriction of dietary K+, stop K+ sparing diuretics, ACEi etc, give dextrose and insulin, sodium bicarbonate
Treat acidosis - protein restrict, sodium bicarbonate
What are the indications that an AKI patient needs dialysis?
Increased K+ Metabolic acidosis Fluid overload (All not responding to normal treatment) Presence of dialysable nephrotoxin Signs of uraemia
What is the prognosis for uncomplicated ATN?
Recovery in 2-3 weeks if no extra insults
What is the overall AKI mortality?
24%
What is the normal GFR range?
90 - 120 ml/min
How many nephrons do we have and how many do we need to survive?
2 million
Need 40,000 approx (2%) to survive
What is chronic kidney disease?
Long term condition
Abnormal kidney function and/or structure
The irreversible and sometimes progressive loss of renal function over a period of months to years
What is the commonest cause of CKD?
Unknown
Name some causes of CKD
Unknown Immunological - glomerulonephritis Infection - pyelonephritis Genetic - PCK, Alport Obstruction and reflux nephropathy Hypertension Vascular Systemic disease - diabetes, myeloma
What is the common end point for the kidneys of many CKDs?
Small, shrunken kidney
With irregular outline
Lots of fibrous scarring
Who should be screened by CKD?
Diabetes
Hypertension
Ischaemic heart disease
Who is CKD more common in?
Elderly
Ethnic minorities
Multi-morbid people
Socially disadvantaged
What is CKD classification based on?
GFR
Describe the stages of CKD
G1 >90 G2 60-89 G3a 45-59 G3b 30-44 G4 15-29 G4 < 15
Which measures of GFR are not very accurate?
> 60 GFR
Other than GFR, what other measurement can we look at?
ACR
Albumin:creatinine ratio
Higher it gets = worsened condition
What are the stages of ACR?
A1 < 3
A2 3 - 30
A3 > 30
What percentage of the adult population have CKD 3 or worse?
Approx 7%
Risk of death starts to increase when kidney function has declined by what percentage?
25%
Even though no symptoms
What indicators what make us check kidney function?
High BP
Proteinuria
Haematuria
Proteinuria and CKD together increase the risk of …
Death by cardiovascular disease
More likely to need dialysis
What is the normal serum creatinine?
80 - 120 micromoles/L
What clearance markers can we use to represent eGFR?
Creatinine
Inulin
Cr EDTA
Iohexol
What are the problems with using clearance markers to estimate GFR?
Expensive
Require hospital stays
Collecting urine has bad compliance
Is the relationship between serum creatinine and GFR linear?
No
How much of your renal function can you lose before serum creatinine will change?
~ 60%
Creatinine concentration in serum is determined by:
Renal function Muscle mass (age, sex, race, exercise)
Why can’t we use eGFR in AKI?
Can only use the eGFR formula if GFR is relatively stable
What can we look for in blood to indicate the cause of CKD?
Autoantibody screen Complement Immunoglobulin ANCA CRP SPEP/UPEP
Describe polycystic kidneys
Autosomal dominant
Can become very large
Have CKD from the day they are born by definition but usually an issue until later in life
Acidosis can affect which organs?
Muscles
Bones
Renal function decline further
Acidosis is not a problem until GFR is …
< 25
How does CKD lead to anaemia?
Decreased production of EPO
Increased resistance to EPO (uraemic environment)
Reduced RBC lifespan
How do we treat anaemia from CKD?
Give EPO subcutaneous injections
How can CKD cause mineral and bone disorders?
Decreased GFR leads to increased serum phosphate and decreased serum calcium
Increased production of PTH
Decreased active vitamin D - decreased Ca2+ gut absorption
What types of renal osteodystrophy can occur?
Rugger jersey spine - sclerosis of end plates
Erosion to terminal phalanges
Bone cysts
What are vertebral end plates?
The top and bottom portions of vertebral bodies that interface with vertebral discs
What other non-bone calcification can occur in CKD?
Aorta
Shoulder joint
Small vessels in skin
What can we do to help prevent/delay CKD?
Stop smoking Increased exercise Lose weight Treat diabetes Treat BP Treat proteinuria (ACEi) Lipid lowering
When is renal replacement therapy usually needed? (GFR)
GFR = 8 - 10 ml/min
What are the indications in CKD for dialysis?
Uraemic symptoms Acidosis Pericarditis Fluid overload Hyperkalaemia
