Pathophysiology of Acute & Chronic Renal Failure

Question 1

What is acute renal failure?

Answer 1

Urine output of less than 500mL per day - a failure of filtration

Question 2

Is acute renal failure reversible?

Answer 2

yes

Question 3

What is chronic renal failure?

Answer 3

GFR of less than 72L/day

Question 4

Is chronic renal failure reversible?

Answer 4

no

Question 5

Does acute renal failure lead to chronic renal failure?

Answer 5

not usually

Question 6

What causes different outcomes of acute renal failure?

Answer 6

the degree of tubular impairment relative to filtration impairment

Question 7

What are the endocrine effects of chronic renal failure?

Answer 7

excessive activation of RAS which will vasoconstrict and impair renal blood flow, vitamin D activation which will cause osteodystrophy and rickets, and EPO which will cause anemia

Question 8

Why is urea a poor indicator of GFR?

Answer 8

because it varies with diet and liver function and steroid use

Question 9

What is a good measure of GFR?

Answer 9

creatinine

Question 10

What is the hydrostatic pressure in the glomerulus?

Answer 10

55mmHg

Question 11

What is the hydrostatic pressure in Bowman’s capsule?

Answer 11

15mmHg

Question 12

What is the oncotic pressure in the glomerulus?

Answer 12

30mmHg

Question 13

What is the net filtration pressure?

Answer 13

10mmHg

Question 14

What is oliguria?

Answer 14

decreased urine production (less than 500mL)

Question 15

What is anuria?

Answer 15

no urine

Question 16

What are the three types of causes of acute renal failure?

Answer 16

pre renal, renal and post renal

Question 17

What is the key cause in pre renal acute renal failure?

Answer 17

systemic blood pressure <45mmHg

Question 18

What are the causes of pre renal acute renal failure?

Answer 18

shock, haemorrhage, sepsis, hypoalbuminemia, renal artery stenosis, NSAIDs, ACE inhibitors, cardiac failure

Question 19

Why does hypoalbuminemia cause renal failure?

Answer 19

because it causes plasma volume to go down so leads to decreased perfusion of kidneys

Question 20

What are the causes of renal acute renal failure?

Answer 20

glomerular disease, interstitial nephritis or tubular damage from ischaemia or toxins (acute tubular necrosis)

Question 21

What toxins cause tubular damage?

Answer 21

antibioics, X-ray contrast media, myoglobin and haemoglobin

Question 22

When is there an increase in haemoglobin?

Answer 22

haemolysis

Question 23

When is there an increase in myoglobin?

Answer 23

rhabdomyolysis

Question 24

What is acute tubular necrosis?

Answer 24

death of tubular epithelial cells caused by hypotension and nephrotoxic drugs - one of the most common causes of acute renal failure

Question 25

What are the 2 ways that acute renal failure can cause death?

Answer 25

acidosis and hyperkalemia

Question 26

What are the post renal causes of acute renal failure?

Answer 26

obstruction - e.g. stones, tumours, benign prostatic hypertrophy

Question 27

What is chronic renal failure?

Answer 27

an irreversible loss of renal function

Question 28

What is glomerular hyper filtration?

Answer 28

in chronic renal failure the remaining nephrons hypertrophy which will cause them to function at too high a level which will cause glomerular hypertension causing further damage - furthermore the tubules are overwhelmed and can’t adequately reabsorb

Question 29

What is the urine like when there is glomerular hyper filtration?

Answer 29

high output of urine that is similar to plasma - has not been modified by tubules

Question 30

What is uraemia?

Answer 30

an accumulation of uraemic toxins - mostly urea = end stage renal disease

Question 31

What are the symptoms of uraemia?

Answer 31

fatigue, loss of appetite, skin pigmentation, nausea, vomiting, dehydrations, priuritus, thrombocytopaenia

Question 32

What are some common causes of chronic renal failure?

Answer 32

diabetes, high blood pressure, chronic glomerulonephritis, cystic disease

Question 33

What happens to salt and water balance in a glomerular chronic renal failure?

Answer 33

sodium retention and hypertension

Question 34

What happens to salt and water balance in a tubular chronic renal failure?

Answer 34

sodium wasting and low BP

Question 35

What happens to potassium in chronic renal failure?

Answer 35

tends to rise

Question 36

What happens to pH in chronic renal failure?

Answer 36

tends to fall

Question 37

What happens to phosphate in chronic renal failure?

Answer 37

increase

Question 38

What happens to calcium in chronic renal failure?

Answer 38

decrease

Question 39

What causes renal osteodystrophy?

Answer 39

low vitamin D3 and high PTH

Question 40

What can cause anuria?

Answer 40

renal artery occlusion and prostatic malignancy

Question 41

How is vitamin D activated?

Answer 41

dual hydroxylation - first in the skin and second in the kidney

Question 42

What type of diet should be given for chronic renal failure?

Answer 42

low protein diet