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 BUN/creatinine ratio  

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Why does BUN/creatinine ratio increase when you have GI bleeding??


Because you have hemmorhage (spelling??) and you are hypotensive therefore your GFR is decreased, therefore increased plasma BUN/Creatinine.


so called prerenal uremia


It should be clear that you really need to be in shock or true volume depketion for the prerenal azotemia to occur. So the GI hemorrhage should be severe, I can not assume a prerenal azotemia without the lab values.


The Ans is simple Anything which causes th eGFR to dec for a Longer period of times will give a lot of things such as Inc. BUN? Creatinine ration among other things


well there are two things

HEMORRHAGE causes MORE UREA plus more products like RBCs to be present in GIT which are broken down by BACTERIA which increases NITROGEN inside GIT which is absorbed more as compared to the normal base line nitrogen absorption...and definitely if there is RENAL FAILURE then GFR will decrease but as you guys know for that a lot of HYPOTENSION is required......the prerenal azotemia doesnt occur so EASILY ..... usually chronic blood loss doesnt cause GFR changes....but it does change the ratio...
the above rationale is the reason that the patients of CIRRHOSIS when develop GI bleed are given LACTULOSE ...previously NEOMYCIN .... so to clear bacteria and hence decrease FORMATION OF AMMONIAIC NITROGEN occurs and the patient can be saved from goin into HEPATIC ENCEPHALOPATHY...hope it helps!!..


excellent explanation SmokyWaters!

And when you have mentioned hepatic encephalopathy, just to add that diet without proteins, prevention of GI bleeding and killing bacteria are three important factors for treating it, since all those three contribute to lowering level of NH3


smokywaters, hate to say it but your wrong. i used that exact same reasoning with my attending today and looked like a total idiot. where did you read that?!

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