Why Renal Tubular Acidosis is normal gap metabolic acidosis? - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
Home
USMLE Articles
USMLE News
USMLE Polls
USMLE Books
USMLE Apps
Go Back   USMLE Forums > USMLE Step 1 Forum

USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 01-12-2010
USMLE Forums Scout
 
Steps History: ---
Posts: 26
Threads: 17
Thanked 13 Times in 7 Posts
Reputation: 23
Kidney Why Renal Tubular Acidosis is normal gap metabolic acidosis?

what is the mechanism of renal tubular acidosis being a normal gap metabolic acidosis? please be so kind as to explain.
thanks in advance
Reply With Quote Quick reply to this message
The above post was thanked by:
anoop_1198 (05-21-2010), Seetal (03-12-2010), wahaha007 (01-13-2010)



  #2  
Old 01-12-2010
USMLE Forums Scout
 
Steps History: 1+CK+CS
Posts: 32
Threads: 13
Thanked 251 Times in 24 Posts
Reputation: 281
Default

  • anion gap = Na - Cl and HCO3
  • metabolic acidosis means low bicarb
Therefore, in any metabolic acidosis you'll have increased anion gap unless the chloride compensates for the depressed bicarb.
Therefore, any normal anion gap metabolic acidosis is essentially hyperchloremic metabolic acidosis. See normal anion gap mnemonic thread

In proximal renal tubular acidosis you have failure of bicarbonate reabsorption and this will be compensated by chloride reabsorption to maintain neutrality across the renal tubule membrane. See this thread for a similar issue
Reply With Quote Quick reply to this message
The above post was thanked by:
Abdulaziz (02-21-2012), anoop_1198 (05-21-2010), dr.burhan (01-12-2010), lichen70 (06-17-2015), Linc (02-20-2016), Seetal (03-12-2010), Thrax_usmle (03-12-2013), usmleguy (04-26-2010), wahaha007 (01-13-2010)
  #3  
Old 01-13-2010
USMLE Forums Scout
 
Steps History: ---
Posts: 26
Threads: 17
Thanked 13 Times in 7 Posts
Reputation: 23
Default

Quote:
Originally Posted by Ahmed-USMLE View Post
  • anion gap = Na - Cl and HCO3
  • metabolic acidosis means low bicarb
Therefore, in any metabolic acidosis you'll have increased anion gap unless the chloride compensates for the depressed bicarb.
Therefore, any normal anion gap metabolic acidosis is essentially hyperchloremic metabolic acidosis. See normal anion gap mnemonic thread

In proximal renal tubular acidosis you have failure of bicarbonate reabsorption and this will be compensated by chloride reabsorption to maintain neutrality across the renal tubule membrane. See this thread for a similar issue
thank you. what i really want to know is what is the mechanism for hyperchloremia. in rta. is an ion pump involved?
Reply With Quote Quick reply to this message
The above post was thanked by:
anoop_1198 (05-21-2010), kalampakas (03-04-2012), lichen70 (06-17-2015)
 
  #4  
Old 01-13-2010
USMLE Forums Scout
 
Steps History: 1+CK+CS
Posts: 32
Threads: 13
Thanked 251 Times in 24 Posts
Reputation: 281
Default

Quote:
Originally Posted by hippocampus View Post
thank you. what i really want to know is what is the mechanism for hyperchloremia. in rta. is an ion pump involved?
Yes, in the proximal convoluted tubules you have 60% reabsorption of Sodium and that's coupled with 15% bicarb and 45% Chloride absorption to maintain electrical neutrality.
When that 15% bicarb decrease (such as Type II RTA) then the 45% Chloride absorption increases and there you have the hyperchloremia.
Reply With Quote Quick reply to this message
The above post was thanked by:
anoop_1198 (05-21-2010), DrSeddik (01-13-2010), kalampakas (03-04-2012), mazrodin (03-14-2010), shahra (03-21-2010), Thrax_usmle (07-23-2013), wahaha007 (01-13-2010)
  #5  
Old 01-13-2010
USMLE Forums Scout
 
Steps History: ---
Posts: 26
Threads: 17
Thanked 13 Times in 7 Posts
Reputation: 23
Default

Quote:
Originally Posted by Ahmed-USMLE View Post
Yes, in the proximal convoluted tubules you have 60% reabsorption of Sodium and that's coupled with 15% bicarb and 45% Chloride absorption to maintain electrical neutrality.
When that 15% bicarb decrease (such as Type II RTA) then the 45% Chloride absorption increases and there you have the hyperchloremia.
thanks a million for this. it makes perfect sense.
Reply With Quote Quick reply to this message
  #6  
Old 03-11-2010
USMLE Forums Scout
 
Steps History: Step 1 Only
Posts: 21
Threads: 10
Thanked 73 Times in 13 Posts
Reputation: 103
Default urine anion gap is also important

Just wanted to add here that in RTA you also have something called the urine anion gap.
The urine anion gap = (Na+) - Cl-
In RTA because we fail to excrete NH4Cl then we have low chloride in urine the urine anion gap is positive unlike the other causes of normal anion gap acidosis (such as diarrhea) where have a negative urine anion gap
Reply With Quote Quick reply to this message
The above post was thanked by:
Ahmed-USMLE (03-11-2010), Linc (02-20-2016), manaranam (04-29-2014), Seetal (03-12-2010), Taiwan_Guy (07-25-2011), thelostsoul (06-19-2016)



Reply

Tags
Acid-Base-, Physiology-, Renal-

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
Where you live. Leave blank if you don't want to tell.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
MUDPILES and Normal Anion Gap Acidosis samirde USMLE Step 1 Mnemonics 4 07-25-2011 05:48 AM
Why Hypokalemia in Renal Tubular Acidosis laila44 USMLE Step 1 Forum 2 05-01-2011 02:16 PM
can someone please explain anion gap metabolic acidosis? DoctorB USMLE Step 1 Forum 3 03-29-2011 10:31 PM
Aspirin Overdose; Respiratory Alkalosis or Metabolic Acidosis deyneko USMLE Step 1 Forum 8 02-21-2011 10:45 AM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)