endrit
Forum Newbie
Topics: 1
Posts: 11
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I've tried this at usmleasy.com please someone tell me the step one is not gona be like this
Which one of the following will be increased in a patient suffering from persistent diarrhea?
Answer Choices C: Correct answer B: Your answer
A. The filtered load of HCO3–
B. The production of ammonia by the proximal tubule
C. H+ secretion by the distal nephron
D. The anion gap
E. The production of new bicarbonate by the distal nephron
Explanation
Persistent diarrhea will result in a metabolic acidosis, due to the loss of the bicarbonate-rich secretions from the pancreas and gallbladder. The ensuing metabolic acidosis will decrease the plasma concentration of HCO3–, decreasing the amount of bicarbonate that is filtered into the proximal tubule. At the same time, the metabolic acidosis will increase ammonia production by the proximal tubule as well as H+ secretion and production of new bicarbonate by the distal nephron. Because the metabolic acidosis is produced by the loss of bicarbonate, the anion gap will remain within normal limits.
I had chosen B but the good answer was C. How come?
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| hiwa
Forum Senior
Topics: 15
Posts: 185
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the ammonia NH3 should combine with H(to be excreted) to become NH4 (ammonium) so basically ammonia just used as a H excretion tool , that is the base of compensation for the metabolic acidosis.
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| Ajazzy
Forum Newbie
Topics: 3
Posts: 13
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Ammonia NH3 production is more specific for distal nephron not proximal, here fore PROTON SECRETION in distal nephron in form of NH4+ would be the better choice
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Good luck guys !
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| Sakaki-
Forum Senior
Topics: 1
Posts: 238
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Ajazzy, I could just be misunderstanding, but doesn't ammonia production occur in the proximal tubule? Like hiwa said, it is a mechanism for excreting H+ ions.
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| GS
Forum Newbie
Topics: 7
Posts: 22
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Persistant diarrhoea
A)--->not correct because bicarbonate levels are in fact reduced due to loss in diarrhoeal fluids
b)---->Ammonia production is definately increased in the PCT which helps in buffering of the hydrogen ions
D)----There is normal anion gap coz there is actually hyperchloremic metabolic acidosis in diarrhoea in the early stages
e)---the production of new bicarbonate by the distal nephrons increases in the distal nephron which is also renal compensation mech in the early stages
C)---this seems like the most correct answer because the key here is persistant ----which means that additional compensatory mechanism are brought into play by the kidneys which actually start to secrete H+ ions directly into the lumen in distal tubule
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| endrit
Forum Newbie
Topics: 1
Posts: 11
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the explanation came from the web site usmleasy.com.
my problem is that i see nothing wrong with choices -increased production of amonia and increased production of bicarbonate. so to me the question was pretty much biased and the explanation just make feel i'm right about it
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