US Lecture 8 - What happened when the kidneys stop working? Flashcards
What happens when the kidneys stop working?
Loss of excretory, homeostatic, endocrine function and abnormality of glucose homeostasis NB: clinical features are determined by rate of deterioration
Why is excretory function lost when the kidneys stop working?
Accumulation of waste products
Why is homeostatic function lost when the kidneys stop working?
Disturbance of electrolyte balance, loss of acid-base control, inability to control volume homeostasis
Why is endocrine function lost when the kidneys stop working?
Loss of erythropoetin production, failure to synthesise 1 alpha hydroxylase vitamin D
Why is there abnormality of glucose homeostasis when the kidneys stop working?
Decreased glucogenesis
What are some symptoms of renal failure?
Extreme lethargy, weakness and anorexia; clinically volume depleted -> severe hypotension, elevated plasma urea and creatinine and it is complicated by hyperkalaemia, hyponatraemia, metabolic acidosis and anaemia. NB: kidneys become small and shrunken
What causes the symptoms of lethargy and anorexia in renal dysfunction?
Accumulation of nitrogenous waste products, hormones, peptides, acidosis, hyponatraemia, volume depletion (low BP), anaemia, chronic neurological damage (peripheral neuropathy)
In patients with renal dysfunction what occurs to the water and salt retention?
Usually difficulty excreting salt and water, leading to tendency to retain Na causing hypertension, peripheral/pulmonary oedema BUT salt and water loss can be found in patients with tubulointerstitial disorders where the concentrating mechanisms have been damaged
What causes the salt and water imbalance in renal dysfunction?
Inability to decrease Na excretion when Na depleted, osmotic diuresis caused by conc of small waste substances, inappropriately high loss of salt and water results in volume depletion which causes low BP
What are the implications of acidosis?
Caused by decreased excretion of H+ and by retention of acid bases; buffered by H+ passing into cells in exchange for K+, so ^ tendency of hyperkalaemia; compensation mechanism inc. increasing CO2 loss through lungs (Kussmahl resp); exacerbates anorexia and increases muscle catabolism
What are the implications of hyperkalaemia?
Caused by failure of DCT to secrete K and is exacerbated by acidosis which causes shift of K from IC to EC space
What does hyperkalaemia cause?
Cardiac arrhythmias and arrest; can affect neural and muscular activity and clinical features of hyperkalaemia are dependent on the chronicity of the hyperkalaemia
What are the features of an ECG of a person with hyperkalaemia?
T waves peak, then T waves disappear > bradycardia > QRS broadens

What are the kidney’s metabolic functions and what happens if they are not carried out?
Decreased erythropoietin production in renal failure results in anaemia. Low 1-25 Vit D levels result in poor intestinal Ca absorption, hypocalcaemia and hyperparathyroidism
What is the mechanism by which phosphate retention decreases Ca2+?

What is a major outcome for patients with CKD?
CV disease

What does an increased CV risk lead to?
Hypertension, secondary cardiac effects, endothelial effects and lipid abnormalities
How can you tell the difference between acute/chronic loss of kidney function?
Acute: Renal size is unchanged and previously normal creatinine levels. Chronic: Renal size often reduced, chronic uraemic symptoms and previously abnormal creatinine levels
What are the initial forms of management of loss of kidney function?
IV normal saline to correct fluid depletion, IV sodium bicarbonate to correct acidosis, IV insulin and dextrose to lower plasma K and dialysis
What are the traditional methods of assessing GFR?
Urea -> poor indicator as it is confounded by diet, catabolic state, GI bleeding. Creatinine -> affected by muscle mass, sex, age, race. Creatinine Clearance -> difficult for elderly patients and overestimates GFR at low GFR. Inulin clearance -> laborious used for research only. Radionuclide studies -> EDTA clearance, reliance but expensive
How is GFR assessed now?
Eqn which automatically calculates estimated GFR from serum creatinine and result is normalised for race -> MDRD but it is unreliable in GFR>60ml/min and in very obese/thin patients
What is the long term management of kidney failure?
Remain on haemodialysis 4h, 3x/week, low K diet and fluid restriction, erythropoietin injections to correct anaemia, 1,25 Vit D supplements to prevent hyperparathyroid bone disease
How is respiratory alkalosis/acidosis reached and compensated for?

How is metabolic alkalosis/acidosis reached and compensated for?












