Lecture 21: Clinical problem solving - Renal failure

Question 1

What is kidney failure?

Answer 1

Reduction in glomerular filtration rate

It is associated with:

• High potassium
• Uraemia (Symptoms)
• Low creatinine
• Oliguria (Can be)

Question 2

What do you want to know when a patient comes in?

Answer 2

History = Symptoms

Examination = Signs

Question 3

PATIENT 1 comes in with: No fever, reduced urine output, no symptoms of infeciton, no pain, no SOB.

Is this AKI or CKD? what can you do to investigate or confirm?

Answer 3

You cant tell if this is AKI or CKD

You can investigate by:
- Examination

Question 4

You examine PATIENT 1 and find:

• Afebrile
• Looks unwell
• BP 90/60
• Dry skin
• Chest clear
• JVP = 0cm

Can you now tell if this is AKI or CKD? what can you do next?

Answer 4

You suspect this is AKI because of the low BP = Dehydration (+ No SOB + Reduced urine output)

Cant 100% tell, so you order blood work to confirm

Question 5

Patient 1; Blood work comes back showing

Urea 12.2mmol/L
Creatinine 441 umol/l
eGFR 9 ml/min/1.73m2
Na 140 mmol/L
K 4.5 mmol/L

Interpret these

Answer 5

Urea Normal = 3.2 -7.7, thus is high
Creatinine normal = 50-100, thus is really high
eGFR = low

Na normal = 135-145, thus is normal
K normal = 3.5-5.3, thus is normal

Interpretation: Definite kidney failure

Question 6

You have seen the bloods for patient one and they indicate renal failure, what other bloodwork could you order to distinguish if this is acute or chronic?

Answer 6

• ESR
• Liver function test
• Haemoglobin (most imp. here b/c will be low in chronic (EPO impacted etc)
• Calcium (also low in CKD)
• Phosphate (high)

Question 7

Why is Hb low in CKD?

Answer 7

Kidney produces EPO which stimulates RBC production. In chronic disease it stops producing this.

Question 8

Patient one further blood work shows normal HB, normal Ca and normal phosphate. Based on the previous evidence what is your diagnosis?

Answer 8

Acute Kidney Injury

Question 9

Based on your diagnosis of AKI in paitent one, what is the likely cause?

Answer 9

Pre-renal

b.c decreased GFR and low BP

Question 10

What might be the cause of low BP and lowered GFR in patient one?

Answer 10

Generally low BP:

• Bleeding
• Sepsis
• Dehydration
• HF

Question 11

What is a potential complication of low BP and GFR in patient one?

Answer 11

Can progress into intrinsic renal damage i.e ATN

Question 12

What mainly causes ATN?

Answer 12

Pre-renal causes of decreased GFR that were not treated quickly enough i.e

• Aminoglycosides
• NSAIDS
• Rhabdomyolosis i.e breakdown of muscles is toxic waste that can damage kidneys i.e crush injury

Question 13

RPGN causes nephritic syndrome and rapid acute renal failure, what is found here? and what causes it?

Answer 13

• Crescents in glomeruli on biopsy
• Red cells and casts in urine
• > SLE
• > Vasculitis
• > Post streptococcal GN

Question 14

What is the best test for post renal AKI and why?

Answer 14

Renal ultrasound is best

• Palpation of bladder doesnt work for obstructions if higher
• Urine volume varies hugely
• Palpation of kidneys might detect a major cyst
• Haematuria detection isnt true for all post renal AKI

Question 15

PATIENT TWO comes in with: BP 180/90, chest clear, no pericardial rub, history of diabetes and hypertension.

What are your initial impressions and what would you look for?

Answer 15

High blood pressure and hypertension, check for signs of fluid overload:

• Oedema
• Difficulty lying down
• JVP
• SOB

Order bloods!

Question 16

Patient two bloods come back:

Urea: 11.4
Creatinine: 635
Phosphate 2.32
Albumin 25
HB and RBC low

Whats your interpretation? What next?

Answer 16

Urea, creatinine, phosphate are all high. Albumin are low. HB and RBC low

High creatinine and urea = Renal failure, thus low GFR
Low HB and RBC = Chronic renal failure

Ultrasound to visualise the kidney would be next step

Question 17

Why does Hb drop in chronic kidney disease?

Answer 17

RBC lifespan is 120days so in acute EPO might go down but the impact on RBC count is not seen…

Question 18

What does a drop in RBC count do to the heart?.

Answer 18

Increases the work of the heart

Question 19

Why does phosphate elevate in CKD? and whats the knock on effects?

Answer 19

Kidneys normal excrete phosphate, decreased excretion means bones increase FGF23, which decreases kidney expression of factors causing it to feedsback to the gut to decrease phosphate and Ca reabsorption

The decrease kidney factor expression also causes increase PTH

Question 20

In patient 2, what is been looked for with an ultrasound?

Answer 20

Presence of obstruction
and
Kidney size: Changes size (inc or dec) depending on cause (CKD = kidneys shrink, <8cm very likely chronic)

Question 21

What are the likely causes of chronic renal failure?

Answer 21

• Diabetes
• Hypertension
• Glomerular disease

Question 22

What is the best treatment to prevent deterioration in chronic kidney disease for patient two?

Answer 22

• Tight HBA1c control
• Treat the anaemia
• Treat the BP
• Dialysis (last resort, keeps alive)

Question 23

What blood pressure treatment works best in CKD?

Answer 23

ACE inhibitors b/c have preferential effect for kidneys,

Dec AGN2
= Dec BP
= Dec NaCl

Dilates efferent arteriole

instead of Beta blockers or diuretics