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21 Cards in this Set
- Front
- Back
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What is the normal ratio of Bun: Creatinine?
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15
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How is creatinine processed?
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Creatinine is filtered and neither absorbed or secreted
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How is Urea Processed?
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Urea is filtered and partly reabsorbed in the proximal tube.
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Bun:Cr ratio depends on changes at several times:
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1) Before the kidneys (prerenal)
2) Within the kidney parenchyma (Renal) 3) After the kidneys (Postrenal) |
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What does azotemia refer to?
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An increase in serum BUN and creatinine
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What causes Prerenal Azotemia?
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Decrease in C.O., leads to a decrease in GFR
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What is the ratio for Prerenal Azotemia?
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>15
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How does a decrease in C.O. lead to a decrease in GFR?
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Hypoperfusion of kidneys
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Is there intrinsic parenchymal renal disease in Prerenal Azotemia?
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NOOOOOO!
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What are some examples of pre-renal azotemia?
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Blood Loss, CHF
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Why is the Serum BUN:CR ratio below 15?
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1) Decreased GFR causes creatinine and urea to back up in blood.
2) After filtration, some urea is reabsorbed in the blood. ***All the creatinine is excreted in the urine 3) Addition of urea in blood increases the ratio over 15 |
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What is the cause of Renal Azotemia?
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Caused by parenchymal damage to the kidneys
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What are some examples of causes of Renal Azotemia?
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Acute tubular necrosis, Chronic Renal Failure
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What is the Serum BUN:Cr ratio for Renal Azotmeia?
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15 or below
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Explain why the BUN:CR ratio is 15 below?
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1) A decreased GFR causes creatinine and urea to back up in blood: Increased extra-renal loss of urea
2) After filtration, both urea and creatinine are lost in the urine ***Proximal tubule cells are sloughed off renal failure |
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Look at BUN and Creatinine: EX: 80mg/dl BUN and serum creatinine: 8mg/dl. What is it?
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BUN/CR ratio is 10 so Renal Azotemia!
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What is the cause of Post- renal Azotemia?
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Caused by urinary obstruction below the kidneys
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Is there intrinsic parenchymal disease in Post-renal Azotemia?
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NOOOO intrinsic parenchymal disease
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Give some examples of Post-renal azotmeia
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Examples: Prostate hyperplasia, Blockage of ureters by stones/cancer
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Explain the mechanism for a SERUM BUN: Cr ratio greater than 15!
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1) Obstruction to urine flow decreases the GFR
2) Back-up of urea and creatinine in the blood 3) Increased tubular pressure causes back-diffusion of urea (not creatinine) into blood ( ratio >15) |
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What does persistent obstruction cause?
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Renal Azotemia Ratio < 15
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