Lecture 9: Clinical Renal Failure and tests

Question 1

Renal Failure means

Answer 1

reduced GFR (<100ml/min) This can be ‘Acute Kidney injury’ or ‘Chronic Kidney Disease’

Question 2

How do you know the patient has renal failure?

Answer 2

Mainly done through Blood tests, often no specific symptoms, -Creatinine (from muscles) -Urea

Question 3

Plasma urea is?

Answer 3

-Main excretory product for waste Nitrogen -~35 g/day formed in liver from aa -Main solute in urinw

Question 4

What does the amount of formed urea depend on?

Answer 4

1) Dietary protein intake 2) Protein breakdown 3) Bleeding into GIT

Question 5

Whats the renal handling of urea

Answer 5

-Freely filtered, with a variable fraction reabsorbed -This fraction increases when flow-rate is slow (eg; dehydrated patient) Excretion rate depends on GFR

Question 6

How does urea change with renal failure and how do we use this change clinically?

Answer 6

Plasma urea rises in renal failure. We can test levels as a rough index of glomerular function (not as good as creatinine as there are so many other variables; protein, hydration, GI bleed etc)

Question 7

______ rises more then ______ in dehydration

Answer 7

Urea rises more then creatinine in dehydrationn

Question 8

Creatinine

Answer 8

-Derived from creatine in muscle, no function = WASTE PRODUCT -Rate of production proportional to muscle mass!!!

Question 9

As creatinine is freely filtered and no tubular reabs./secretion so…

Answer 9

Creatinine clearance rate is proportional to GFR, plasma creatinine rises as GFR falls

Question 10

How can you get a falsely elevated creatinine?

Answer 10

1. Protein intake 2. Muscle Mass also… 3. Fish/meat meal can cause a rise of 10-40umol/L (as cr. formation occurs in food especially during cooking) This can give a falsely low GFR (blood sample should be take +12hr after meal)

Question 11

eGFR

Answer 11

Estimated GFR: via plasma Creatinine (used as other tests are too impractical). Via calculators Done on the basis that it describes the amount if muscle waste product produced, and how well the kidneys get rid of this!!

Question 12

Factors in eGFR

Answer 12

-Weight (muscle or fat?) -Age -Gender These are done on population norms.

Question 13

Limitations of eGFR

Answer 13

if muscle mass is unusually high or low (amputees, muscle wasting, body builders) If patients don’t have a steady-state creatinine.

Question 14

Acute Kidney Injury

Answer 14

-Sudden rapid reduction in GFR (days/weeks) -Usually reversible -70% due to non-renal causes (pre-renal, renal, post-renal)

Question 15

Pre-renal AKI. What is it and what causes it?

Answer 15

Reduction in renal blood flow leading to a reduction in GFR. Due to low BP: -Dehydration, shock, haemorrage, cardiogenic shock, severe bilat. renal art. stenosis

Question 16

How do we diagnose pre-renal AKI?

Answer 16

1. History: reasons for low BP: hydration, bleeding, infection, chest pain 2. Check urine output: often oliguric <1L/day 3. Blood test: creatinine, high K+, high phosphate, low Ca2+

Question 17

Treatment for pre-renal AKI. Outcomes??

Answer 17

Fix the underlying problem: eg; rehydrate, treat bleed, fix heart, ABs etc Outcomes: 1) Patient gets better 2) Acute Tubular Necrosis (renal)

Question 18

Renal AKI

Answer 18

80% Acute Tubular Necrosis:

• Mainly due to pre-renal (also drugs and toxins)
• Oliguria and renal failure even after underlying cause is fixed
• 4-6wk recovery

Glomerulinephritis

Question 19

ATN blood tests will show

Answer 19

-High creatinine -Low urine output (oliguria) -High Potassium

Question 20

Treatment of renal AKI

Answer 20

Maintain normal BP and treat underlying issue. If it continues to worsen do dialysis ~<10ml/min GFR (NOT TREATMENT JUST KEEPS YOU ALIVE)

Question 21

Recovery stats of renal AKI

Answer 21

95% Pulyuric phase in Recovery: -tubules can’t concentrate -upto 20L urine.day -Need IV fluids to compensate

Question 22

Rapidly Progressive Glomerulinephritis (RPGN)

Answer 22

-Glomerular disease -Blood and/or protein in urine

Question 23

Post-renal causes and best way to disagnose

Answer 23

Anything that BLOCKS/SQUASHES -Kidney stones -Tumour -Prostate hypertrophy -Urinary retention Ultrasound very useful!!

Question 24

Chronic Kidney disease. What would blood tests show?

Answer 24

-Over months/years -Gradual decline in kidney function -IRREVERSIBLE -Elevated creatinine, urea (normal urine output)

Question 25

Stages of Chronic Kidney Disease and the consequences associated

Answer 25

..

Question 26

Causes of CKD. How does it occur?

Answer 26

• Diabetes
• GLomerulonephritis
• Hypertension

Gradual increase in creatinine due to underlying disease → scarring of glomeruli and interstitium.

Question 27

Ureamia: symptoms of kidney Failure

Answer 27

• Anorexia
• Nausea/vomiting
• itchness
• cold intolerance
• swelling
• Seizures/coma

Question 28

Patient Symptoms(feelings)/signs of CKD

Answer 28

Nothing till later stages.

Then ureamai and hypertensive

maybe also oedema, raised JVP

Question 29

How do you diagnose CKD?

Answer 29

Via Bloodtests

Urea: increased
Creatinine: increased
eGFR: decreased
**Haemoglobin (differentiating test): Low and takes ~120 to show

Question 30

Bone disease and CKD

Answer 30

Kidneys are required to produce the active form of Vit D. If not functioning → bone disease

Question 31

High serum Phosphate and CKD

Answer 31

Unable to excrete phosphate from preserved food.

Can lead to parathyroid hormone syrdrome