Clinical Nephrology

Question 1

What is the endocrine role of the Kidney?

Answer 1

Produces erythropoietin in response to hypoxia and performs the hydroxylation of 1-(OH)D3 (hydroxycholecalciferol) to produce calcitriol

Question 2

What happens after Kidney failure?

Answer 2

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

Question 3

What can happen to electrolyte levels during Kidney failure?

Answer 3

Hyponatraemia (leading to volume depletion) if problem with tubules, hypernatraemia if difficulty excreting sodium

Hyperkalaemia if excreting sodium (risk of arrhythmias - pointed T-waves)

Question 4

How can renal failure cause lethargy?

Answer 4

Likely to have high plasma urea and creatinine (toxic so cause lethargy)

Question 5

What are the endocrinological consequences of Renal failure?

Answer 5

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

Question 6

What are the implications of Renal failure for the CV system?

Answer 6

Risk of MI increased (CKD greater predictor than smoking)

Question 7

What happens to Salt and water levels during renal failure?

Answer 7

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

Question 8

How does renal failure cause acidosis?

Answer 8

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

Question 9

What are the risks of abnormal Potassium levels for the heart?

Answer 9

Hypokalaemia: risk of VF (sigmoid T-waves)

Hyperkalaemia: risk of asystole (pointed T waves, QRS broadening and loss of P waves)

Question 10

What are the signs of Loss of Kidney function?

Answer 10

Anaemia, acidosis, hyperkalaemia, hyponatraemia tendency, oedema and hypertension

Question 11

What are five tests for measuring GFR?

Answer 11

Urea
Creatinine
Creatinine clearance
Inulin Clearance
Radionuclide studies

Question 12

Why is Urea not used to test GFR?

Answer 12

Poor indicator and confounded by diet, GI bleeding, drugs and liver function

Question 13

What are the advantages and disadvantages of Creatinine testing?

Answer 13

Rapid and cheap

Affected by muscle mass (higher), age, race, sex (higher in men), diet

Question 14

What are the disadvantages of a creatinine clearance test?

Answer 14

Difficult for elderly patients and overestimates low GFR

Question 15

What are the advantages and disadvantages of Inulin clearance testing?

Answer 15

Laboratory gold standard

Laborious and not used in practice

Question 16

What are the advantages and disadvantages of Radionuclide studies?

Answer 16

E.g. EDTA clearance - reliable

Expensive tho

Question 17

What is eGFR?

Answer 17

Estimated GFR - uses equations to calculate GFR from serum creatinine and patient factors such as age, ethnicity and sex; unreliable when GFR > 60ml/min

Question 18

What is the general method of action of Diuretics?

Answer 18

Reduce sodium reuptake to retain water within the urine

Question 19

Give an example of a loop diuretic and how it works:

Answer 19

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)

Question 20

What are Thiazides?

Answer 20

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)

Question 21

What are osmotic diuretics?

Answer 21

Glucose/mannitol act as solutes to reduce the osmotic gradient and decrease water reabsorption (act on PCT/dLoH)

Question 22

What are carbonic anhydrase inhibitors?

Answer 22

Inhibits carbonic anhydrase to reduce sodium reabsorption because fewer protons are available for the Na+/H+-ATPase pump

Question 23

What are K+ Sparing diuretics?

Answer 23

Amiloride blocks sodium channels and spironolactone is an aldosterone antagonist (inhibits sodium channel and Na+/K+-ATPase) - small effect (can affect 3-5% load)

Question 24

What do urine dipsticks test for?

Answer 24

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

Question 25

What is renal replacement therapy?

Answer 25

Advanced CKD may necessitate haemo(dialysis) and/or transplant to replace the function of the kidneys

Question 26

When is dialysis usually first started?

Answer 26

Usually started at GFR = 10ml/min or when indicated e.g. uraemia, severe hyperkalaemia, and uncontrolled acid-base disturbances

Question 27

What is Haemodialysis?

Answer 27

Pumping blood via artificial kidneys where blood surrounded by electrolyte fluid to control solute, waste and water concentration of blood returned to body; can be done several times a week or daily, and at hospital or at home; risks of hypotension, infection and inflammation

Question 28

What is peritoneal dialysis?

Answer 28

Dialysate fluid pumped into peritoneal cavity, with peritoneal capillaries acting as blood source; ultrafiltration controlled by altering osmolality of the dialysate; allows a more independent life; risk of back pain, infection, catheter problems and peritonitis

Question 29

What is renal transplantation, including where it is placed, and when it is contraindicated:

Answer 29

Provides best long term outcomes, and may come from living/cadaveric donors; new kidney placed extraperitoneally in the iliac fossa; requires immunosuppression so contraindicated in AIDS, infection and cancer

Question 30

What dietary modifications should be given in renal failure?

Answer 30

Avoidance of high salt food as sodium will not be removed
Low potassium foods
Consideration of phosphate intake (not usually a problem in early CKD)
Do not restrict protein
Fluid restriction in advanced CKD
VitD supplementation
Iron tablets if anaemic