Back again for my 2nd #tweetorial on urine electrolytes. Next up is urine chloride (UCl).
1/
In my (limited) clinical experience, UCl is ordered/utilized/discussed far less compared to its buddy ion UNa. Should it be this way? Lets explore.
First, a question. When do you order UCl?
In my (limited) clinical experience, UCl is ordered/utilized/discussed far less compared to its buddy ion UNa. Should it be this way? Lets explore.
First, a question. When do you order UCl?
2/
I imagine many would say to evaluate unexplained metabolic alkalosis given the classic teaching of chloride-responsive vs chloride-resistant metabolic alkalosis. However, I’m still waiting for one of these enigmatic cases.
I imagine many would say to evaluate unexplained metabolic alkalosis given the classic teaching of chloride-responsive vs chloride-resistant metabolic alkalosis. However, I’m still waiting for one of these enigmatic cases.
3/
Others may order it to calculate the urine anion gap (UAG) in evaluation of an unexplained NAGMA. While RTAs are under recognized, they are still uncommon disorders.
NOTE: for great teaching on RTAs & the UAG, see the #tweetorials by @justinberk & @amyaimei(links at the end)
Others may order it to calculate the urine anion gap (UAG) in evaluation of an unexplained NAGMA. While RTAs are under recognized, they are still uncommon disorders.
NOTE: for great teaching on RTAs & the UAG, see the #tweetorials by @justinberk & @amyaimei(links at the end)
4/
So what’s left? Lets take a step back.
One of the guiding principles of human physiology is the maintenance of electroneutrality. In regards to the ECF compartment, which two ions are the most abundant?
So what’s left? Lets take a step back.
One of the guiding principles of human physiology is the maintenance of electroneutrality. In regards to the ECF compartment, which two ions are the most abundant?
5/
Na & Cl! Given this, shouldn’t our applications (and nuances/caveats) for UNa apply to UCl as well?
Yes, they do! In fact, using them together can improve clinical utility. Back to #Aragorn to illustrate:
Na & Cl! Given this, shouldn’t our applications (and nuances/caveats) for UNa apply to UCl as well?
Yes, they do! In fact, using them together can improve clinical utility. Back to #Aragorn to illustrate:
6/
Aragorn stops at The Shire to picnic w/ his hobbit friends. While Sam is a skilled gardener, his potato salad leaves much to be desired. Unfortunately, a severe vomiting illness quickly spreads through the picnickers & even the mighty Aragorn cannot escape.
Aragorn stops at The Shire to picnic w/ his hobbit friends. While Sam is a skilled gardener, his potato salad leaves much to be desired. Unfortunately, a severe vomiting illness quickly spreads through the picnickers & even the mighty Aragorn cannot escape.
7/
~1 day later and 5lbs lighter, his symptoms begin to lighten. At this time, what would we expect his volume/total body salt status to be?
~1 day later and 5lbs lighter, his symptoms begin to lighten. At this time, what would we expect his volume/total body salt status to be?
8/
We’d expect it to be low, given his volume loss from vomiting. As such, what do we expect his [UNa] to be?
We’d expect it to be low, given his volume loss from vomiting. As such, what do we expect his [UNa] to be?
9/
We’d expect it to be low…but it returns at 42mEq/L. Why might that be?
We’d expect it to be low…but it returns at 42mEq/L. Why might that be?
10/
Bicarbonaturia! Vomiting leads to a met alkalosis that drives compensatory urinary bicarb excretion. This excess bicarb binds Na, leading to the higher than expected [UNa] value. This also helps to maintain the all-important electroneutrality!
Bicarbonaturia! Vomiting leads to a met alkalosis that drives compensatory urinary bicarb excretion. This excess bicarb binds Na, leading to the higher than expected [UNa] value. This also helps to maintain the all-important electroneutrality!
11/
This is where UCl comes in. In a state of volume depletion, what would we expect [UCl] to be?
This is where UCl comes in. In a state of volume depletion, what would we expect [UCl] to be?
12/
We’d expect it to be low, indicating an appropriate response by the kidney to a low volume state.
NOTE: Like [UNa], some sources use [UCl]<15mEq/L as the cut off for an appropriate response to a prerenal state.
We’d expect it to be low, indicating an appropriate response by the kidney to a low volume state.
NOTE: Like [UNa], some sources use [UCl]<15mEq/L as the cut off for an appropriate response to a prerenal state.
13/
Lets draw some conclusions w/ the info thus far:
-Using [UNa] & [UCl] together can improve diagnostic accuracy of volume status over either in isolation.
-A value of <20mEq/L for either is indicative of a salt-retaining state (i.e. ⬇️effective arterial blood volume=EABV).
Lets draw some conclusions w/ the info thus far:
-Using [UNa] & [UCl] together can improve diagnostic accuracy of volume status over either in isolation.
-A value of <20mEq/L for either is indicative of a salt-retaining state (i.e. ⬇️effective arterial blood volume=EABV).
14/
With the principles above, lets discuss the expected clinical scenarios for the 4 possible UNa, UCl combinations.
When would we expect to see a low UNa & UCl?
With the principles above, lets discuss the expected clinical scenarios for the 4 possible UNa, UCl combinations.
When would we expect to see a low UNa & UCl?
15/
We’d expect to see this combination in states of decreased EABV. This could occur w/ hypovolemia, such as from lack of PO intake, or in Na-avid states such as CHF, cirrhosis, and CKD.
When would we see a low UNa & high UCl?
We’d expect to see this combination in states of decreased EABV. This could occur w/ hypovolemia, such as from lack of PO intake, or in Na-avid states such as CHF, cirrhosis, and CKD.
When would we see a low UNa & high UCl?
16/
We’d expect to see this combo in states of ⬇️ EABV. This could occur w/ hypovolemia 2/2 diarrhea, where the resulting metabolic acidosis (&hypoK) leads to ⬆️NH4 excretion w/ consequent ⬆️ Cl excretion to maintain electoneutrality.
When would we see a high UNa & low UCl?
We’d expect to see this combo in states of ⬇️ EABV. This could occur w/ hypovolemia 2/2 diarrhea, where the resulting metabolic acidosis (&hypoK) leads to ⬆️NH4 excretion w/ consequent ⬆️ Cl excretion to maintain electoneutrality.
When would we see a high UNa & low UCl?
17/
Again, we’d expect to see this combo in states of ⬇️EABV. Think back to Aragorn:vomiting leading to metabolic alkalosis and bicarbonaturia is a classic scenario. Another non-reabsorbable anion effect(ex. ketoanion, drugs such as piperacillin) could also explain this scenario.
Again, we’d expect to see this combo in states of ⬇️EABV. Think back to Aragorn:vomiting leading to metabolic alkalosis and bicarbonaturia is a classic scenario. Another non-reabsorbable anion effect(ex. ketoanion, drugs such as piperacillin) could also explain this scenario.
18/
Beyond history, urine pH can be used to help to determine the identity of this anion. See the pic below for further explanation.
Beyond history, urine pH can be used to help to determine the identity of this anion. See the pic below for further explanation.
19/
PEARL: Accuracy ranges widely w/ dipstick pH measurements w/ a margin of error as high +/- 1 pH unit. As such, if you wish to use urine pH to help w/ clinical interpretation, a separate urine pH test, measured via a pH electrode, should be ordered.
PEARL: Accuracy ranges widely w/ dipstick pH measurements w/ a margin of error as high +/- 1 pH unit. As such, if you wish to use urine pH to help w/ clinical interpretation, a separate urine pH test, measured via a pH electrode, should be ordered.
20/
Finally, when would we see a high UNa & UCl?
Finally, when would we see a high UNa & UCl?
21/
This is a little tougher. We could see this combination in states of⬇️EABV. This includes tubular dysfunction, such as w/ diuretic use or tubulopathies (ex. Bartter & Gitelman syndromes).
This is a little tougher. We could see this combination in states of⬇️EABV. This includes tubular dysfunction, such as w/ diuretic use or tubulopathies (ex. Bartter & Gitelman syndromes).
22/
However, this could also be seen in states of⬆️EABV, such as may occur w/ excess IVF administration or in states of mineralocorticoid excess (ex. Conn syndrome).
However, this could also be seen in states of⬆️EABV, such as may occur w/ excess IVF administration or in states of mineralocorticoid excess (ex. Conn syndrome).
23/
Additionally, an AGMA – w/ excretion of Na salts of the excess acid & NH4Cl to attempt to offset the extra-renal acidemia – could lead to this combination as well.
Additionally, an AGMA – w/ excretion of Na salts of the excess acid & NH4Cl to attempt to offset the extra-renal acidemia – could lead to this combination as well.
24/
A lot of information, so lets summarize w/ a graphic (see below).
A lot of information, so lets summarize w/ a graphic (see below).
25/
One last point. What electrolyte disturbance is often seen w/ volume depletion and subsequent RAAS activation?
Hypokalemia! As you might have guessed, UCl & UNa have been found to helpful in the assessment of chronic, normotensive hypokalemia.
One last point. What electrolyte disturbance is often seen w/ volume depletion and subsequent RAAS activation?
Hypokalemia! As you might have guessed, UCl & UNa have been found to helpful in the assessment of chronic, normotensive hypokalemia.
26/
Interestingly, in this study (ncbi.nlm.nih.gov/pubmed/28213045), it outperformed UK, TTKG, & UK/UCr in the diagnosis of extrarenal causes of hypokalemia, in particular anorexia/bulimia & laxative abuse.
Interestingly, in this study (ncbi.nlm.nih.gov/pubmed/28213045), it outperformed UK, TTKG, & UK/UCr in the diagnosis of extrarenal causes of hypokalemia, in particular anorexia/bulimia & laxative abuse.
27/
Fin. Take Aways summarized in pic below.
Fin. Take Aways summarized in pic below.
28/
-While I don’t think this #tweetorial will increase my frequency of testing for UNa or UCl, I do think I will no longer order one without the other.
-While I don’t think this #tweetorial will increase my frequency of testing for UNa or UCl, I do think I will no longer order one without the other.
29/
I’ll think to use UNa & UCl for the following scenarios:
-assessment of dysnatremias
-unexplained acid-base disturbances– including metabolic alkalosis, NAGMA
-challenging volume status assessment
-diuretic response
-unexplained chronic, normotensive hypokalemia
I’ll think to use UNa & UCl for the following scenarios:
-assessment of dysnatremias
-unexplained acid-base disturbances– including metabolic alkalosis, NAGMA
-challenging volume status assessment
-diuretic response
-unexplained chronic, normotensive hypokalemia
30/
When do you use UCl #medtwitter, #nephtwitter?
@kidneyboy @NephroGuy @rabihmgeha @doc_connors @KylieAdamek @GlassockJ @NephRodby @medrants @NephroMD @drlessing @edgarvlermamd @RenalFellowNtwk @stuartlinas @JohnRMontford @sargsyanz @ABRezMed @KourtneyKing
When do you use UCl #medtwitter, #nephtwitter?
@kidneyboy @NephroGuy @rabihmgeha @doc_connors @KylieAdamek @GlassockJ @NephRodby @medrants @NephroMD @drlessing @edgarvlermamd @RenalFellowNtwk @stuartlinas @JohnRMontford @sargsyanz @ABRezMed @KourtneyKing
References:
DOI: 10.2215/CJN.10330818
DOI: 10.1152/ajprenal.00130.2018
DOI: 10.1016/j.amjmed.2017.01.023
DOI: 10.1681/ASN.2010121289
PMID: 7077808
DOI: 10.2215/CJN.10330818
DOI: 10.1152/ajprenal.00130.2018
DOI: 10.1016/j.amjmed.2017.01.023
DOI: 10.1681/ASN.2010121289
PMID: 7077808
https://twitter.com/justinberk/status/1020994327995088896?s=20
https://twitter.com/amyaimei/status/1179819512813764609?s=20
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