Clinical Nephrology Flashcards
What is the endocrine role of the Kidney?
Produces erythropoietin in response to hypoxia and performs the hydroxylation of 1-(OH)D3 (hydroxycholecalciferol) to produce calcitriol
What happens after Kidney failure?
Loss of excretory functions (toxins)
Loss of homeostatic function (electrolytes, acid-base, volume state)
Loss of endocrine (erythropoietin production and VitD hydroxylation)
Abnormality of glucose homeostasis
What can happen to electrolyte levels during Kidney failure?
Hyponatraemia (leading to volume depletion) if problem with tubules, hypernatraemia if difficulty excreting sodium
Hyperkalaemia if excreting sodium (risk of arrhythmias - pointed T-waves)
How can renal failure cause lethargy?
Likely to have high plasma urea and creatinine (toxic so cause lethargy)
What are the endocrinological consequences of Renal failure?
Anaemia results due to reduced erythropoietin synthesis
Lower 1,25-(OH)2VitD3 and increased PTH because phosphate retention and low levels of calcitriol lead to hyperparathyroidism
What are the implications of Renal failure for the CV system?
Risk of MI increased (CKD greater predictor than smoking)
What happens to Salt and water levels during renal failure?
Renal dysfunction can lead to difficulty in salt and water excretion, causing hypertension, oedema and pulmonary oedema; osmotic diuresis occurs due to urea and inability to decrease sodium excretion when depleted leads to hypotension
How does renal failure cause acidosis?
Decreased proton excretion and base retention; buffered by protons entering cells in exchange for potassium ions (increases hyperkalaemia); Kussmahl’s respiration (air hunger), breathing rapidly and deeply to attempt to compensate for metabolic acidosis
What are the risks of abnormal Potassium levels for the heart?
Hypokalaemia: risk of VF (sigmoid T-waves)
Hyperkalaemia: risk of asystole (pointed T waves, QRS broadening and loss of P waves)
What are the signs of Loss of Kidney function?
Anaemia, acidosis, hyperkalaemia, hyponatraemia tendency, oedema and hypertension
What are five tests for measuring GFR?
Urea Creatinine Creatinine clearance Inulin Clearance Radionuclide studies
Why is Urea not used to test GFR?
Poor indicator and confounded by diet, GI bleeding, drugs and liver function
What are the advantages and disadvantages of Creatinine testing?
Rapid and cheap
Affected by muscle mass (higher), age, race, sex (higher in men), diet
What are the disadvantages of a creatinine clearance test?
Difficult for elderly patients and overestimates low GFR
What are the advantages and disadvantages of Inulin clearance testing?
Laboratory gold standard
Laborious and not used in practice
What are the advantages and disadvantages of Radionuclide studies?
E.g. EDTA clearance - reliable
Expensive tho
What is eGFR?
Estimated GFR - uses equations to calculate GFR from serum creatinine and patient factors such as age, ethnicity and sex; unreliable when GFR > 60ml/min
What is the general method of action of Diuretics?
Reduce sodium reuptake to retain water within the urine
Give an example of a loop diuretic and how it works:
e.g. Furosemide block the Na/K/Cl transporter of the ascending loop of Henle, leading to reduced movement of sodium into the lining and hence retention of electrolytes and water in the urine - most potent (can affect up to 25% load)
What are Thiazides?
Block the Na+/Cl- transporter in the DCT, reducing sodium uptake, but also meaning that the Na+/Ca2+ exchanger on the basolateral surface becomes more active so more calcium is reabsorbed - (can affect 5-10% load)
What are osmotic diuretics?
Glucose/mannitol act as solutes to reduce the osmotic gradient and decrease water reabsorption (act on PCT/dLoH)
What are carbonic anhydrase inhibitors?
Inhibits carbonic anhydrase to reduce sodium reabsorption because fewer protons are available for the Na+/H+-ATPase pump
What are K+ Sparing diuretics?
Amiloride blocks sodium channels and spironolactone is an aldosterone antagonist (inhibits sodium channel and Na+/K+-ATPase) - small effect (can affect 3-5% load)
What do urine dipsticks test for?
Blood: indicates kidney/GU tract damage
Urobilinogen: liver disease
Bilirubin: biliary obstruction or liver disease
Protein: usually negative - protein indicates renal disease
Nitrite: produced by bacteria - indicate infection
Ketones: not usually present - can indicate disruption to carbohydrate metabolism
Glucose: should not normally be present - could indicate diabetes
pH: usually 5-9
Leukocytes: may indicate infection
