Pathophysiology of Acute & Chronic Renal Failure Flashcards
What is acute renal failure?
Urine output of less than 500mL per day - a failure of filtration
Is acute renal failure reversible?
yes
What is chronic renal failure?
GFR of less than 72L/day
Is chronic renal failure reversible?
no
Does acute renal failure lead to chronic renal failure?
not usually
What causes different outcomes of acute renal failure?
the degree of tubular impairment relative to filtration impairment
What are the endocrine effects of chronic renal failure?
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
Why is urea a poor indicator of GFR?
because it varies with diet and liver function and steroid use
What is a good measure of GFR?
creatinine
What is the hydrostatic pressure in the glomerulus?
55mmHg
What is the hydrostatic pressure in Bowman’s capsule?
15mmHg
What is the oncotic pressure in the glomerulus?
30mmHg
What is the net filtration pressure?
10mmHg
What is oliguria?
decreased urine production (less than 500mL)
What is anuria?
no urine
What are the three types of causes of acute renal failure?
pre renal, renal and post renal
What is the key cause in pre renal acute renal failure?
systemic blood pressure <45mmHg
What are the causes of pre renal acute renal failure?
shock, haemorrhage, sepsis, hypoalbuminemia, renal artery stenosis, NSAIDs, ACE inhibitors, cardiac failure
Why does hypoalbuminemia cause renal failure?
because it causes plasma volume to go down so leads to decreased perfusion of kidneys
What are the causes of renal acute renal failure?
glomerular disease, interstitial nephritis or tubular damage from ischaemia or toxins (acute tubular necrosis)
What toxins cause tubular damage?
antibioics, X-ray contrast media, myoglobin and haemoglobin
When is there an increase in haemoglobin?
haemolysis
When is there an increase in myoglobin?
rhabdomyolysis
What is acute tubular necrosis?
death of tubular epithelial cells caused by hypotension and nephrotoxic drugs - one of the most common causes of acute renal failure
What are the 2 ways that acute renal failure can cause death?
acidosis and hyperkalemia
What are the post renal causes of acute renal failure?
obstruction - e.g. stones, tumours, benign prostatic hypertrophy
What is chronic renal failure?
an irreversible loss of renal function
What is glomerular hyper filtration?
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
What is the urine like when there is glomerular hyper filtration?
high output of urine that is similar to plasma - has not been modified by tubules
What is uraemia?
an accumulation of uraemic toxins - mostly urea = end stage renal disease
What are the symptoms of uraemia?
fatigue, loss of appetite, skin pigmentation, nausea, vomiting, dehydrations, priuritus, thrombocytopaenia
What are some common causes of chronic renal failure?
diabetes, high blood pressure, chronic glomerulonephritis, cystic disease
What happens to salt and water balance in a glomerular chronic renal failure?
sodium retention and hypertension
What happens to salt and water balance in a tubular chronic renal failure?
sodium wasting and low BP
What happens to potassium in chronic renal failure?
tends to rise
What happens to pH in chronic renal failure?
tends to fall
What happens to phosphate in chronic renal failure?
increase
What happens to calcium in chronic renal failure?
decrease
What causes renal osteodystrophy?
low vitamin D3 and high PTH
What can cause anuria?
renal artery occlusion and prostatic malignancy
How is vitamin D activated?
dual hydroxylation - first in the skin and second in the kidney
What type of diet should be given for chronic renal failure?
low protein diet
