7.4 Chronic Kidney Disease & Renal Failure Flashcards
What is CKD?
Abnormalities of kidney structure or function, present for >3 months
What GFR parameter defines CKD?
GFR <60mL/minute
What are the symptoms of CKD? (4)
Albuminuria/proteinuria, haematuria, electrolyte abnormalities detected by imaging
What endocrine functions are performed by the kidneys?
Erythropoietin synthesis
1-alpha hydroxylase for vitamin D
What homeostatic functions are performed by the kidneys? (3)
Electrolyte balance
Acid-base balance
Volume homeostasis
What are the excretory functions of the kidneys? (5)
Nitrogenous waste
Middle sized molecules
Hormones
Peptides
Salt and water
What are the functions of the kidney regarding glucose metabolism?
Gluconeogenesis
Insulin clearance
Disruptions to the homeostatic balance of the kidneys can manifest as what? (4)
Hyperkalaemia
Reduced bicarbonate – decreases pH, manifests as metabolic acidosis
Increased phosphate
Salt and water imbalance
What are the endocrine imbalances that occur in kidney dysfunction?
Increased PTH
Anaemia – reduced EPO production
Hypocalcaemia – reduced calcitriol synthesis
Why is there parathyroid hyperplasia associated with kidney dysfunction?
Decreased renal 1-alpha hydroxylase leads to decreased calcitriol synthesis
This manifests as chronic hypocalcaemia, which causes raised PTH for increased bone resorption
Why does anaemia occur in kidney dysfunction?
Reduced erythropoeitin production
What do reduced 1-25 Vit D levels cause in kidney failure?
Reduced intestinal calcium absorption
Hypocalcaemia
Hyperparathyroidism
How does chronic renal failure contribute to the effects of reduced 1-25 Vit D?
Phosphate retention is seen in chronic renal failure
This contributes to low levels of 1-25 Vit D and hypocalcaemia, thus hyperparathryoidism
What are the symptoms associated with kidney failure and reduced secretion of sodium chloride?
Hypertension
Oedema
Pulmonary Oedema
Why is salt and water loss evident in tubulointestinal disorders?
Damage to the concentrating mechanism of urine – thus water reabsorption is decreased
Why is water and salt loss seen right after a kidney transplant?
There is damage to the tubules and they pee out a lot of water
Why does metabolic acidosis occur in kidney failure?
Reduced excretion of hydrogen ions from the distal convoluted tubule cells into the filtrate, manifests as acid retention
Why is salt and water loss seen after kidney obstruction is relieved?
The kidney can’t concentrate urine and you get kidney failure
What can cause AKI?
Hypovolaemia
What does hyponatremia mean and what does it not mean?
It does not mean reduced total body sodium
It’s to do with how much free water you have - you’ll have more in hyponatremia
How do we treat hyponatremia?
Remove the excess free water (instead of giving extra salt)
What does acidosis do to K+ ions in renal failure?
In response to acidosis (more H+ in blood), cells take up more H+ ions, which forces K+ out of cells, leading to hyperkalaemia
What are the 2 causes of hyperkalaemia?
Acidosis
Reduced distal tubule potassium secretion
What is used to treat hyperkalaemia in an acute setting?
Sodium bicarboante – neutralises the hydrogen ions, such that potassium can re-enter the cells
What can acidosis cause?
Anorexia and muscle catabolism
What are the symptoms of hyperkalaemia?
Cardiac arrhythmias
Disrupt neural and muscular activity
Vomiting
What does symptom presentation depend on in hyperkalaemia?
Chronicity of the disease
If acute hyperkalaemia – symptoms will show
If chronic – body adapts, symptoms don’t show
What features on an ECG suggest hyperkalaemia?
Peaked T waves
P-waves – broaden, reduced amplitude, disappear
QRS widening
Heart block
Asystole
Ventricular tachycardia/ventricular fibrillation
What type of hyperparathyroidism is linked with chronic kidney failure?
Tertiary hyperparathyroidism
Why is there an increased cardiovascular risk with chronic kidney disease?
Cardiac ventricular myocyte contraction is directly related to extracellular concentrations of calcium (arrythmias) + increased calcification risk
What is the major predictor of end stage renal failure?
CKD
What standard cardiovascular risk is there for kidney failure patients?
Hypertension
Diabetes
Lipid abnormalities
What additional risks are there for kidney failure patients?
Inflammation
Oxidative stress
Mineral/bone metabolism disorder
What is the major outcome for a patient with CKD, and what does this mean?
Major outcome is cardiovascular disease
Means CKD patients are more likely to die from cardiovascular disease than end stage renal failure
What is the immediate treatment in a patient with hypovolaemia?
Give fluids
What is the immediate treatment for a patient with hypervolaemia?
Fluid restriction, consider diuretics/dialysis
What are the 3 main ways we manage hyperkalaemia?
- Drive potassium into cells
- Drive it out of body – diuretics/dialysis
- Reduce gut absorption – potassium binders
What are the 2 ways we can manage hyperkalaemia by driving K+ into cells?
- Sodium bicarbonate – H+ comes out of cell into blood to equalise this, and K+ goes back into the cell
- Insulin dextrose
Why do we need to be careful with insulin dextrose?
Fatalities associated with it due to hypoglycaemia
Only used when potassium >6.5 or when there are ECG changes
What does conservative treatment for CKD include? (5)
- Erythropoietin injections to correct anaemia
- Diuretics to correct salt-water overload
- Phosphate binders – for hyperphosphataemia, reduces itching
- 1-25 Vitamin D supplements
- Symptom managements – e.g. nausea
What home therapy is available for CKD?
- Haemodialysis
- Peritoneal dialysis/assisted programmes
The peritoneum behaves as a semipermeable membrane and a dialysate is delivered with specific concentrations (hyperosmolar to generate drive, fluid into the peritoneal cavity)
What in centre therapy is available for CKD?
Haemodialysis, 4 hours 3 times a week
What is a fistula in terms of CKD?
A fistula is created by connecting an artery directly to the vein – vein swells for ease of access
Where should taking blood be avoided in patients with renal failure?
Avoid taking blood from the veins of the anterior cubital fossa or cephalic vein at wrist level
Which veins should be used when taking blood or IV lines for patients with renal failure?
Dorsal venous structures
Why should transfusions be avoided in patients with renal failure?
Transfusions will sensitise anaemia (haemolytic anaemia, as foreign antigens are detected, and antibodies are formed)
This increases the risk of autoimmune mediated rejection of transplanted kidney
Why is urea a poor indicator of GFR?
Confounded by diet, catabolic state, GI bleeding (bacterial breakdown of blood in gut), drugs, liver function etc
What factors affect creatinine within patients with renal failure?
Affected by muscle mass, age, race and sex
So we need to look at the specific patient when using creatinine to assess kidney function
What factors limit how useful creatinine clearance is for assessing kidney function? (2)
It overestimates GFR at a low GFR (as a small amount of creatinine is normally secreted into urine)
It’s also difficult for elderly patients to collect an accurate 24 hour urine sample
When is inulin clearance used to assess kidney function?
Research purposes only, as it is laborious
What is the most appropriate radionucleotide study in patients with renal failure?
EDTA
What is the main factor in calculating estimated GFR (eGFR)?
Serum creatinine
What is the difference between actual GFR and eGFR?
As kidneys get better and actual GFR goes up, the eGFR becomes less accurate
So in kidney disease patients with normal eGFR, we look at the creatinine trend
What do we use to classify CKD? (3)
Proteinuria
Albumin:creatinine ratio
GFR
More protein means higher risk of end stage renal failure
