Lecture 19: Clinical renal failure Flashcards
What is kidney failure?
- A reduction in GFR
(Normally 100ml/min)
Acute Kidney Disease
vs
Chronic Kidney injury
What are the signs of renal failure?
Blood test:
- Elevated creatinine
- Elevated urea as renal failure continues
What is the staging for AKI based on serum creatinine or urine output?
Must know
Stage 1: Serum creatinine 1.5->1.9x baseline. OP <0.5ml/kg/hr urine 6-12hrs
Stage 2: 2.0->2.9x baseline. OP <0.5ml/kg/hr urine >12hrs
Stage 3: 3x baseline. OP <0.3ml/kg/hr urine >24hrs or 12hrs anuria.
What are the patient risk factors for AKI??
Must know
- Elderly (65+)
- CKD
- Long term conditions i.e CKD, DM, CHF
- Polypharmacy
- Specific meds i.e
-> Diuretic
-> NSAIDS
-> ACEi/BP meds
Why does creatinine elevate in renal failure?
Creatinine is a surrogate measure for:
- How much muscle waste product is produced
- How well the kidneys get rid of the waste product
What is the gold standard of GFR measurement?
- Insulin clearance (injected)
- Using an isotope Cr-EDTA clearance
But these are impractical for everyday clinical use
What is eGFR and what does it use?
eGFR = estiamted GFR and blood test measures creatinine as an indicator of renal function. Many formula exist for this.
What confounds the interpretation of GFR?
- Creatinine is secreted in small amounts by the tubules so adds to overestimates of creatinine clearance.
- Serum creatinine also reflects body size and muscle mass.
- Moderate to severe CKD confounds interpretation. b/c as GFR declines extrarenal excretion increases (also pts have declining muscle mass)
What factors influence eGFR?
- Weight i.e enhanced muscles mass vs fat b/c muscle mass will increase creatinine
- Age, muscle mass declines with age
- Age, GFR declines naturally with age
- Gender, females have less muscle mass
- Race, different ethnicities have different muscle mass
How does eGFR compare with GFR?
Two people with the same creatinine can have completely different GFRs… so eGFR is largely dependant on creatinine and muscle mass
So what two factors are examined when it comes to kidney function?
- GFR (other methods of being calculated) and Creatinine
What are the two types of renal failure and what do they have in common?
Acute Kidney injury
Chronic kidney disease
Both have high creatinine and low GFR
What is acute kidney injury?
- Sudden rapid reduction in GFR
- Happens over days/weeks
- Usually reversible
70% due to non-renal causes
What are the potential aetiologies of AKI?
- Pre-renal (insufficient blood)
- Renal
- Post renal (Obstructions)
What are the causes of prerenal failure?
- Low BP
- Not enough blood to kidneys
- Dehydration, septic shock, haemorrhage, cardiogenic shock , severe renal art. stenosis
What is found on a blood test for pre-renal AKI?
- High creatinine
- K = Hyperkalemia
- Phosphate = High (itchy skin)
- Ca: May be low
Whats the treatment for pre-renal AKI?
Fix underlying problem
- Rehydrate
- Treat bleeding
- Fix heart
- Antibiotics for sepsis
- ICU treatment for persistent low BP
What happens to pre-renal AKI if it doesnt get better?
Potentially leads to acute tubular necrosis
Whats acute tubular necrosis (ATN)?
- Mainly due to pre-renal causes
- Persistant oliguria (low urine) and renal failure after correction of underlying pre-renal condition
-> High creatinine
-> Low urine output
-> High potassium
Necrosis of the tissues, suspected from lack of blood
Whats the treatment for ATN?
- Maintain normal BP
- Treat underlying problem…
- If kidney keeps getting worse then dialysis (not a cure just keeps people alive)
Whats recovery like for ATN?
- 95% get better
Polyuric phase in recovery
- Tubules cant concentrate
- Up to 20L urine per day
- Need IV fluids to recover
What are the renal causes of renal failure?
ATN:
- Pre-renal (as listed earlier)
- Drugs i.e aminoglycosides
- Toxins
Glomerulonephritis
What causes rapidly progressive glomerulonephritis (RPGN)?
- Acute renal failure due to glomerular disease (not drug related)
- Usually presents with blood and or protein in the urine
- AKI
- Diagnosis requires a renal biopsy
What are the causes of post renal AKI?
- Kidney stones
- Tumour
- Prostate hypertrophy
- Urinary retention
What is chronic kidney disease?
- Happens over months/years
- Gradual decline in renal function
- Irreversible (scarring on kindeys)
What is seen with CKD?
- Elevated creatinine
- Elevated urea
- Usually NORMAL urine ouput
What are the markers of kidney damage?
- Structural abnormalities
- Abnormal urine sediment
- Electrolyte abnormality
- Decrease GFR <60ml/min
What are the causes of CKD?
- Diabetes
- Glomerulonephritis
- Hypertension
What happens in CKD?
- Gradual increase in creatinine due to underlying disease
- Scarring of glomeruli and interstitium
What are the patient symptoms of CKD?
- None in early stages
- Usually found on blood tests
- Urine output normal
- Uraemia: Symptom of kidney failure (Not till GFR has got low)
What does uraemia result in?
- Anorexia (B/c so sick doesnt eat)
- Nausea
- Vomiting
- Itchiness
- SOB
- Swelling
- Cold intolerance
- Seizures
- Coma
What are the signs of CKD?
- No consistent signs early on
- Most common is hypertension
- Oedema
- Pulmonary oedema
- Raised JVP
How is CKD diagnosed?
Usually on a routine blood test
- Urea: Increased
- Creatinine: Increased
- eGFR: Decreased
What are the stages of CKD and what are some consequences?
Recreate this slide with the appropriate values for each staage……. check nothing else has been missed.
Stage 1: Normal
Stage 2: Early (Increased PTH)
Stage 3: Moderate (decreased Ca, anaemia, low EPO)
Stage 4: Severe (High phosphate, acidosis, K may rise, malnutrition)
ESRF: Uraemia
Why does phosphate rise in Kidney failure?
Body has a high turn over of phosphate
- Thus most of what is absorbed in excreted in the kidney.
- This in kidney failure, less is excreted and serum phosphate increases.
What happens to Potassium in CKD?
Often high b/c proximal tubule issues
= Arrhythmias
What can you do in CKD?
Aims of therapy:
- Prevent disease progression
- Control complications of renal failure
Chronic -> control of BP (tends to be the aim)
What are the secondary factors likely to contribute to the progression of CKD?
VIP Diabetes!!! Hypertension!!
- intra-glomerular hypertension
- Glomerular hypertrophy
- Ca and Ph
- Dyslipidaemia
- Proteinuria
- Tubulointerstiital fibrosis
- Toxcitiy of iron/NH4
Whats a treatment found to improve all renal outcomes?
VIP
SGLT2i
improves all renal outcomes. Osmotic diuretic? MoA unsure.
Reducing blood pressure…
How is blood pressure suggested to be tackled to improve renal outcomes?
Lifestyle changes
Salt, weight, exercise, smoking
Drugs:
- Diuretics
- SNS, RAAS
Whats the importance of proteinuria?
- An important prognostic factor
- Wide range of GN outcome is determined by the degree of of proteinuria
- Reduction in proteinuria is assc with improved outcomes
How can proteinuria be modified?
- Weight loss
- ACEi + AIIRB
- Aldo antagonists
- Statins
- Moderate protein restrict
- Lowering BP
Whats smoking assocaited with?
Associated with progression of both non-diabetic and diabetic kidney disease.
What happens to Ca and P in CKD?
They are asssociated with progressive renal impairment and decline in renal function.
Improvement in Ca/P product is associated with reduction in rate of decline
How can Ca/P be managed?
- Limit P in diet
- Phosphate binders i.e CaCO4
How does CKD effect water balance?
CKD patients are more prone to both dehydration and volume overload.
How is the kidney an endocrine organ?
- EPO
- Vit D
- BMP
- RAAS
- Bradykinin
What else can happen in CKD?
- Normochromic normocytic anaemia
- Electrolyte abnromalities
- Metabolic acidosis due to lack of excretion
- Uraemia
How do you manage CKD?
- Treat Primary and secondary disease
- Avoid nephrotoxins
- Optomise fluid balance / avoid dehydration
- Correct abnormalities
- Renal replacement therapy
What are the ESKD treatment options?
- Conservative
- Dialysis; Peritoneal, heamodialysis
- Renal transplant
