RENAL Flashcards
(200 cards)
What are the eGFR values for the different stages of CKD
Stage 1: >90 mL/min - normal/ slightly high- only CKD if other evidence of kidney damage
Stage 2: 60-89 - normal - only CKD if other evidence of kidney damage
Stage 3a: 45-59 - low
Stage 3b: 30-44 - moderately low
Stage 4: 15-29 - severely low
Stage 5: <15 - renal failure
At what stage of CKD do you start to see complications
Stage 4 - 15-20 mL/min
What is the ‘steady state’ that is required to measure creatinine, what limitations does this have, and what conditions might you see this in
The steady state is an assumed state where the amount of creatinine produced (from muscle breakdown) is equalised to that excreted from kidneys - so that if you measure serum creatinine and it is high or low this can be interpreted as kidney injury/ failure.
The limitation of this is that, is there is a problem in the kidney it may take some time for serum creatine to rise - t/f falsely reassuring.
Or, certain conditions or people will generate more creatine than normal, eg those with cachexia - muscle wasting - may not reflect kidneys failing. Or liver disease.
Or those with high muscle mass. This will mean their eGRF is underestimated.
What antibiotic can cause an increase in eGFR and why
Trimethoprim. Inhibits creatinine secreation in renal tubule, so get retention in serum. Is not a sign of renal failure.
But also, trimethoprim is nephrotoxic, so also could be!
What level of albuminuria is indicative of glomerular damage
1g upwards
Below this is probably bc of hypertension or CVS
What effects do NSAIDs have on GFR and what is the mechanism
Inhibit prostaglandins
Prostaglandins usually dilate the afferent arteriole
If inhibit these, get vasoconstriction of afferent arteriole
= less blood into glomerus
= decrease in GRF
What effects do ACE inhibitors have on GFR and how
Angiotensinogen II regulates vasoconstriction of efferent arteriole
If block AII by ACE inhibitor = dilation of efferent arteriole
= blood flows through glomerulus quicker
= decrease GFR
What is the most metabolically active areas of the nephron - what injury is this most susceptible to
Proximal - bc most solute re-absorption happens here
tf v susceptible to ischemic injury
What are the main complications of kidney disease
Cardiovascular disease - fluid overload - heart failure
Why are ACE inhibitors or ARBs indicated in proteinuric CKD
They dilate the efferent arteriole which will lower the GFR and decreased protein leak. This also isnt good for kidney but bc proteins injury the nephron it is more beneficial to lower GFR and prevent proteins getting into tubule, basically tolerate drop in GRF to preserve tubule and longer term kidney function.
When should ACEX or ARBs be stopped in pts with CKD
If they get infection/ malaise, bc BP can start to drop, so this + BP drop from ACE inhibitors can facilitate sepsis
What determines K+ excretion in the kidney
Na+ delivery to distal tubule
Aldosterone
*NB- K+ is freely filtered in glomerulus, then reabsorbed in proximal tubule & LoH.
It is exchanged for Na+ in distal and collecting duct. If get increase in Na+ delivery to distal tubule (via loop diuretic, furosemide), will exchange all this for K+ = hypokalemia
What are the main functions of the kidney
Homeostasis -Filtration & reabsorption -Blood pressure - RAAS -Potassium -Acid/ bicarb balance Vitamin D & Bone Erythropoetin
List two side effects of spironolactone
Hyperkalemia Metabolic acidosis (renal tubular acidosis type I)
This is bc, principal cells that have ENac channels (Na+ in exchange for K+) are blocked by spironolactone, so you don’t get movement of K+ from blood into urine in exchange for Na+
K+ is exchanged for H+, If block ENac = decreased K+ in lumen (urine) to exchange with H+ in cells, so retain H+ = acidosis.
List the side effects of loop (furosemide) and thiazide diuretics (distal tubule)
Hypokalemia
Bc, of ENaC channels.
Exchange Na+ for K+. If increase Na+ deliver = increase K+ movement into urine.
Renal tubule acidosis type 1 occurs where in nephron and what drugs can cause it
In collecting ducts - spironolactone can cause it in susceptible ppl - depends on their acid load (think about high protein diet where pt will probably have excess H+)
Renal tubular acidosis type 2 occurs where in nephron - what conditions/ pathology could cause this
In proximal tubule - where 90% of bicarb is reabsorbed
Anything that causes ischemia to these cells - hypotension, sepsis etc - bicarb resorption fails = metabolic acidosis
What are the criteria to identify a AKI
When thinking about AKI, try to remember the rule with:
“2,4,6,8 rule
Doubling
Halving”
1.increase in creatinine of 26 micromols/L within 48 hours
2.Creatinine doubling
Has creatinine gone half way to doubling? 1.5x BL within 7 days
3.Urine halved
Has the patients urine output per hour halved, based on the BW? eg. <0.5 mL/kg/hr in 6 consecutive hrs
BL* can be the best creatinine figure over the last 6 months
How many of the KDIGO criteria do you need for diagnosing AKI
1 out of 3
What blood test should be done if you suspect rhabdomyolisis may have happened in a patient
Bloods for creatinine phosphokinase
Lactate dehydrogenase
(Enzyme that catalyses phosphate groups onto creatinine - these are used as an energy reservoir for highly metabolic tissues, eg skeletal muscle; if muscle breaks down - creatinine kinase is released into blood)
How does rhabdomyolisis cause AKI
Release of muscle contents - myoglobin - protein that when broken down is toxic to kidney
Which gonal vein drains into a renal vein
Left gonadal into left Renal vein
Right gonadal direct into IVC
What is the main medical emergency associated with AKI
Hyperkalemia
Describe what happens in AKI induced hyperkalemia
Potassium is not being excreted by kidneys - increase in serum K+
K+ controls the resting membrane potential of cardiac myocytes and nerves
If serum K+ increases this alters the membrane potential of cardiac cells and inhibits Na+/K+ pump
Myocytes fail to repolarise properly and they accumulate Na+ and Ca2+ in the cell bc of pump breakdown.
=water into myocytes (odema) + contraction without action potential (causes ischemia) + cell undergoes programmes cell death
=this is “depolarisation arrest” - can’t repolarise properly, lose impulse-contraction coupling - ischemia - and cell starts to die.
HR starts to decrease, BP starts to drop
Muscle twitching bc of increased charge in cells