Chronic kidney disease and renal failure Flashcards
What are the basic functions of the kidneys?
Homeostatic functions
Excretory functions
Endocrine functions
Glucose metabolism functions
What homeostatic functions do the kidneys have?
Electrolyte balance
Acid-base balance
Volume homeostasis
What homeostatic derangements occur in kidney disease?
Potassium increases
Phosphate increases
Bicarbonate decreases
pH decreases (metabolic acidosis)
Salt and water imbalance
What excretory functions do the kidneys have?
Nitrogenous waste (urea, creatinine)
Hormones
Peptides
Middle-sized molecules
Salt and water
What types of excretory derangement occurs in kidney disease?
Increase in urea
Increase in creatinine
Decrease in insulin requirement (due to low insulin clearance so more stays in system)
What types of excretory derangement occurs in kidney disease?
Increase in urea
Increase in creatinine
Decrease in insulin requirement (due to low insulin clearance so more stays in system)
What endocrine functions does the kidney have?
synthesis of:
erythropeitin
1-alpha hydroxylase for vitamin D
What happens when endocrine functions of kidney are compromised?
- Decrease in calcium
- Anaemia
- Increase in parathyroid hormone (to compensate for low calcium)
What glucose metabolism functions do the kidneys have?
Gluconeogenesis
Insulin clearance
In kidney disease, what is there an increased overall risk of?
Cardiovascular risk
How does rate of deterioration affect clinical presentation?
- If rate of deterioration is slow, body is very good at adapting e.g. some patients present with urea of 50 (which for a normal person is really bad) but their body is used to it since it’s developed over years so they don’t feel unwell
- Acute renal failure presents quicker because body hasn’t adapted
Give 2 examples of how the cause of kidney failure can dictate the clinical presentation
If you have Goodpasture’s disease where body makes antibodies against glomerular basement membrane, you might present with haemoptysis (lung involvement of Goodpasture’s since antibodies are made against lung too) and then you do blood test and find renal failure in the patient too
If you have skin rash (purpura) and do blood test and find they have renal failure
What can indicate hypovolemia?
Pallor
Decreased capillary refill
Hands cold
Poor skin turgor
Low heart rate
Low BP
JVP not visible
Tachypnoeic
What can cause tachypnoea with normal O2 sats and clear lungs on auscultation?
Respiratory compensation- Kussmaul respiration
What changes will there be in concentrations of urea, creatinine, sodium, potassium and haemoglobin in a hypovolemic patient with chronic kidney injury?
- Urea higher
- Creatinine higher
- Sodium can go up or down
- Potassium higher
- Haemoglobin lower
What changes will there be in pH, pCO2, pO2, HCO3- and base excess in a hypovolemic chronic kidney injury?
- pH will be lower
- pCO2 will be lower as she’s hyperventilating so she’s expelling CO2
- pO2 will be up a bit as she’s hyperventilating so she’s bringing in O2
- HCO3- will be lower
- Base excess will be lower or normal
What causes changes to acid base status in kidney injury
They have increased H+ because less is excreted because of the kidney failure so the patient has metabolic acidosis which is compensated by resp rate increasing to decrease CO2 to shift equation left
What changes will there be in concs of urea, creatinine, sodium, potassium, haemoglobin in acute kidney injury?
- Urea higher
- Creatinine higher
- Sodium could be either
- Potassium higher
- Haemoglobin normal (because it’s acute renal failure so there’s still some EPO around)
What changes will there be in pH, pCO2, pO2 and HCO3- in acute kidney injury?
- pH lower
- pCO2 lower
- pO2 higher
- HCO3- lower
Mild metabolic acidosis with respiratory compensation
Kidney failure leads to reduced secretion of salt and water, leading to?
Hypertension
Oedema
Pulmonary oedema
In what kind of circumstances (kidney injury) can salt and water loss be seen though?
In tubulointerstitial disorders- damage to the concentrating mechanism of urine
Seen right after kidney transplant- there’s a bit of damage to the tubules and you pee out a lot of water
Seen also after kidney obstruction is relieved, kidney can’t concentrate urine and you get kidney failure
What may be a cause of AKI?
Hypovolemia
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
Why is it important to understand that hyponatremia does not mean does not mean reduced total body sodium when treating hyponatremia?
You may not want to give them salt but instead remove the excess free water
Describe how acidosis happens in renal failure.
- Reduced secretion of H+ ions which means you become acidotic
- Cells take up this H+
What happens to K+ when cells take up H+?
The cells taking up the H+ also forces K+ out of the cells leading to hyperkalaemia
What are the 2 causes of hyperkalaemia?
- Acidosis
- Reduced distal tubule potassium secretion
What are the symptoms of hyperkalaemia?
- Cardiac arrhythmias
- Neural and muscular activity
- Vomiting
What does symptom presentation in hyperkalemia depend on?
Chronicity of the disease- if it’s acute hyperkalaemia then these symptoms show but if its chronic then body adapts and they don’t show
What ECG changes come up in hyperkalaemia?
- Peaked T waves
- P waves broaden, have reduced amplitude and disappear
- QRS widening
- Heart block
- Asystole
- VT/VF (ventricular tachycardia/ventricular fibrillation)
What health consequences does hyperkalemia have?
Anorexia
Catabolism
What effects does reduced EPO and reduced 1-25 Vit D levels have?
Reduced EPO–> anaemia
Reduced 1,25 Vit-D–>
-Reduced intestinal calcium absorption
-Hypocalcaemia
-Hyperparathyroidism
What is the result of phosphate retention in chronic renal failure?
- Phosphate is usually excreted by kidneys
- Phosphate retention contributes to low levels of 1-25 vit D and hypocalcaemia and therefore hyperparathyroidism
Chronic renal failure increases the overall risk of what group of conditions?
Cardiovascular
What is the major predictor of end stage renal failure?
CKD
What is the major outcome for a patient with CKD?
Cardiovascular disease- A patient with CKD is more likely to die from cardiovascular disease than end stage renal failure
Diagram of cardiovascular risk during progression of CKD
What standard cardiovascular risk is there for kidney failure patients?
Hypertension
Diabetes
Lipid abnormalities
What additional risks are there for kidney failure patients (non-standard)?
Inflammation
Oxidative stress
Mineral/ bone metabolism disorders
What are the 2 main things we want to treat in initial management of renal failure?
Fluid balance
Hyperkalemia
How do we manage hypovolaemia vs hypervolaemia in renal failure?
- Hypovolaemia- give fluids
- Hypervolaemia- trial of diuretics/dialysis
What are the 3 ways we manage hyperkalemia?
Drive it into cells
Drive it out of the body
Reduce gut absorption
How do we drive potassium into cells?
Sodium bicarbonate
Insulin dextrose
How does sodium bicarbonate work?
- Binds to H+ to push equation to the right
- H+ come out of cell into blood to equalise this and K+ goes back into cell
Why do we need to be careful with insulin dextrose?
- There are fatalities associated with it due to hypoglycaemia
- We only use it when potassium >6.5 or there are ECG changes
Why do we need to be careful with insulin dextrose?
- There are fatalities associated with it due to hypoglycaemia
- We only use it when potassium >6.5 or there are ECG changes
How do we drive K+ out of the body?
Diuretics/ dialysis
How do we reduce gut absorption of K+?
Potassium binders
What different long term management options are there for kidney failure?
Conservative
Home therapy
In-centre therapy
Transplantation
Conservative treatment for renal failure
- EPO injections to correct anaemia
- 1,25 vit D supplements for hypocalcaemia
- Diuretics to correct salt water overload
- Phosphate binders- for hyperphosphataemia so reduces itching
Home therapy for renal failure
- Haemodialysis
- Peritoneal dialysis/assisted programmes
In centre therapy for renal failure
Haemodialysis, 4 hours 3 times a week
Kidney failure risk equation
What is important to keep in mind for managing patients in hospital with kidney disease in terms of taking blood from them?
Take it from the back of the hand and not anterior cubital fossa or cephalic vein at wrist level because we need it for the fistula and it can scar up (stenosis) and we can’t do the fistula
If a patient is fit for transplantation, why do we need to avoid transfusions?
Transfusions sensitise patients to the antigens in the blood of the donor and then if they then get a kidney donation from someone else who shares similar antigens to the blood donor there’s increased risk of transplant failure
What different methods are there for assessing kidney function?
- Urea
- it’s a poor indicator
- Confounded by diet, catabolic state, GI bleeding (bacterial breakdown of blood in gut), drugs, liver function etc
- Creatinine
- It’s affected by muscle mass, age, race, sex etc
- We need to therefore look at the patient when interpreting the result (if they’re small/big, M/F etc)
- We look at the trend of creatinine (if we know what normal creatinine is) which is useful
- Radionuclide studies
- EDTA clearance etc
- Very reliable but expensive
- Used for donors
- Creatinine clearance
- Difficult for elderly patients to collect an accurate 24 hour urine sample
- Overestimates GFR at low GFR (as a small amount of creatinine is also secreted into urine)
- Inulin clearance
Laborious so used for research purposes only - We mainly calculate estimated GFR (eGFR)- Serum creatinine is main factor here
These graphs show difference between actual GFR and eGFR- what does this show?
As kidneys get better and actual GFR goes up, the eGFR becomes less accurate
Therefore, in patients with normal/high eGFR in kidney disease-We look at creatinine trend e.g. someone could have increase in creatinine 30 → 60 but still have eGFR >90 so it won’t be picked up
What do we use to classify CKD
- Proteinuria
- ACR (albumin:creatinine ratio)
- GFR
More protein means more risk of end stage renal failure
