Lecture 13: Clinical renal failure Flashcards
What is kidney failure?
- A reduction in GFR
(Normally 100ml/min)
Acute Kidney Disease
vs
Chronic Kidney injury
Whats the difference between symptoms and signs?
Symptoms = What a patient tells out
Signs = What you find upon examinaton
What are the symptoms of kidney failure?
Symptoms:
- Vomiting
- Loss of appetite
- Fatigue, weakness, sleep issues
- CHANGE IN URINE OUTPUT
- Oedema
- Persistent itching (high phosphorus)
- SOB
- High blood pressure (difficult to control)
What are the signs of renal failure?
Blood test:
- Elevated creatinine
- Elevated urea as renal failure continues
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
- 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
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
Is race widely used in eGFR calculations now?
In some calculators yes, but race is very complex and is starting to no longer be used.
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 pre-renal events can lead to AKI?
Absolute loss of fluid
i.e Mjr haemorrhage, vomiting, diarrhoea, severe burns
Relative loss of fluids
i.e Congestive HF, distribution shock (i.e fluids not being delivered)
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 are the main findings for pre-renal AKI?
Low BP - Postural drop Signs of dehydration - JVP, Tissue tugor (pinch skin, does rebound back) Signs of sepsis - Fever etc Signs of haemorrhage - Bleeding Signs of cardiogenic shock - HF, pulmonary oedema
What happens to urine output in pre-renal AKI?
- Usually low intially
<1L
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
Whats the best way to assess post renal AKI?
Ultrasound
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
Whats is the goal of treating CKD?
Aim to slow down progress
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?
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
How else can stage 3 CKD be measured? and what would you expect and why?
Blood test
- Low EPO because kidney produces EPO and this drives RBC production thus may also be anaemic
How does the failing kidney contribute to bone disease?
Kidney converts the stored form of vitamin D to its active form and that regulates Ca + phosphate absorption in the gut
What bone disease can kidney failure lead to?
Renal oseodystrophy
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.
Why does PTH increase in early stage CKD?
Low Ca and high phosphate stimulate PTH release
Describe how all the factors of CKD lead to renal osteodystrophy?
- High serum phosphate
- Low vit D
- Low Ca
- High PTH
=
- Excessive bone reabsoprtion of Ca
- Fractures
- Extra-osseous calcification
- Vascular calcification
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 is the most common and best treatment of CKD?
Aggressive control of blood pressure
- ACE inhibitor and ARB
