type 2 rta

[The kitchen sink]

hi all,

studying for my cc boards, I came across some conflicting information regarding the topic of type 2 proximal rta. One of my texts says it has a + Urine anion gap (as do rta proximal 1, rta 4) and another one of my texts says it has a - Urine anion gap (with GI losses due to diarrhea for example)?

so.... for board purposes, which one is it?

2nd q is, for hypercholremic metabolic acidosis, does the urine anion gap play any part in figuring this out? my assumption would be that it is negative (unless there is concomitant renal failure) ? as there is nothing wrong with the kidneys and so you should be able to excrete ammonium/chloride pushing the urine anion gap to be negative.

thanks in advance!

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[Chemist0157]

hi all,

studying for my cc boards, I came across some conflicting information regarding the topic of type 2 proximal rta. One of my texts says it has a + Urine anion gap (as do rta proximal 1, rta 4) and another one of my texts says it has a - Urine anion gap (with GI losses due to diarrhea for example)?

so.... for board purposes, which one is it?

2nd q is, for hypercholremic metabolic acidosis, does the urine anion gap play any part in figuring this out? my assumption would be that it is negative (unless there is concomitant renal failure) ? as there is nothing wrong with the kidneys and so you should be able to excrete ammonium/chloride pushing the urine anion gap to be negative.

thanks in advance!

1. UAG may not be very helpful in type 2 RTA as the issue is with poor bicarbonate reabsorption, not ammonium excretion. So, I'd say the real answer is neither.

2. Yes, if +, think poor ammonium excretion. If -, think of electrolyte losses (ex. diarrhea).

UAG does go out the window with kidney disease as the ability to appropriately balance acid, sodium, and potassium excretion is impaired.

 

[The kitchen sink]

i see, well that does help practically, but for the boards do you know what the UAG would be? positive or negative for type 2 rta?

 

[Chemist0157]

i see, well that does help practically, but for the boards do you know what the UAG would be? positive or negative for type 2 rta?

I don't think boards is going to outright ask you the UAG of a proximal RTA. They should give you a clinical situation and more data points like urine pH, BMP, in addition to a UAG.

If you want to provide some context to the discrepancies in your texts, I may be able to help sort it out, but I honestly would not worry about this point very much. Boards should know UAG is not necessarily helpful for proximal RTA. It's even on UptoDate.