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* Type 1 vs type 2 renal tubular acidosis
 #569917  
  2ndtime - 02/23/11 00:12
 
  Is there an error in master the boards/

Type 1:

-Cant secrete H.
-Urine PH is High
-Predisposes to stones
-Dx is by giving acid
-Rx is bicarbonate

Type II:

-Cant absorb bicarbonate
-Urine PH is high
-no stones
-Dx is by giving HCO3
Rx is diuretics

This is what I know. It is opposite to what MTB says.

Please help me out.
 
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* Re:Type 1 vs type 2 renal tubular acidosis
#2337297
  s4ndra - 02/23/11 03:35
 
  you are right, there is an error in MTB....



 
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* Re:Type 1 vs type 2 renal tubular acidosis
#2337903
  grigolia - 02/23/11 18:10
 
  what you wrote it is not different from a new MTB , what mistake do you speak about?  
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* Re:Type 1 vs type 2 renal tubular acidosis
#2339246
  misshyd - 02/25/11 00:04
 
  there is very well explained acid base review in dr.red nephrology, listen to it on their blog and check the notes too. I like these acid base concepts , let us discuss more on these
http://usmlestep3blog.com/usmle-step3-review/archer-usmle-step-3-review/acid-...gy-topic-1/

Renal Tubular Acidosis ( RTA) ( from link above)

A normal gap metabolic acidosis with positive urine anion gap ( UAG) could be due to RTA. There are different types of RTA.
Type 1 ( distal)
Type 2 (proximal)
Type 4 (hyporeninemic hypoaldosteronism)

On the exam, once you identify a metabolic acidosis and then identify an RTA, you will be tested on the etiology of that RTA. So, it is important to know how to differentiate between different RTAs and their causes.

To differentiate between various RTAs, first look at the serum potassium. If K+ is high in an RTA , this is most likely Type 4 ( because low aldosterone causes decreased renal excretion of acid and potsssium) If the potassium is normal or low, then the RTA could be Type 1 (Distal) or Type II (Proximal). You will need to look at the urine pH to differentiate between Distal and Proximal RTA. Remember that Distal RTA can never acidify the urine so, the Urine pH is never less than 5.5. So, if a MCQ gives a urine pH of less than 5,5, you are most likely dealing with Proximal RTA.
Type 1 RTA – Distal RTA :
- Causes: autoimmune diseases ( scleroderma), hyperglobinemia states and hereditary
- Present with normal anion gap acidosis, urine pH >5.5, hypokalemia, hypercalciuria, nephrocalcinosis and stones
- Treatment: alkali i.e. K citrate
Type II RTA – Proximal RTA :
- Failure to reabsorb filtered bicarbonate in the proximal tubule
- Presents with Hypokalemia and normal gap acidosis
- Urine pH > 5.5, but it will be less than 5.5 once serum HCO3 is less than 16
- Causes: Multiple myeloma, Acetozolamide, Ifosfamide Lead, cadmium, copper

Type IV RTA – Hyporeninemic Hypoaldosteronism
- Causes: diabetes mellitus, HIV and tubulo-interstitial disease
- Present with hyperkalemia, normal anion gap acidosis and normal urine pH
Identifying Mixed Acid-Base Disorder in Metabolic acidosis

A) To understand if a patient has both increased anion gap acidosis and non-gap acidosis at the same time or metabolic acidosis + metabolic alkalosis at the same time, you will need to know the concept of “Delta Gap” . Delta gap is logically explained in the video clip below. Logically, if the serum bicarbonate (Hco3-) falls more than the change in the anion gap, then a patient has both non-gap+increased gap acidosis. If the serum bicarbonate falls less than the change in the anion gap, then the patient has mixed disorder – metabolic acidosis + metabolic alkalosis.

For example, if the anion gap is 20 –> you can say the change in the anion gap is 8 ( because normal anion gap is 12. ) In this scenario let us say if the MCQ gave serum hco3- as 10, drop in the serum bicarb here is 14 ( remember, for calculation normal serum bicarb is taken as 24. so, if it is 10 now, the drop in bicarb is obviously, 14). –> this means when your anion gap has increased by 8 your bicarb has fallen more than 8 i.e; by 14….that means some other factor apart from the factor responsible for increased gap acidosis is also contributing to acidosis here! – this suggests co-existing increased anion-gap+normal-gap acidosis . A classic example is diarrhea with shock – where diarrhea causes non gap acidosis but shock can lead to lactic acidosis which increases the gap – so, things can co-exist!
B) To understand if your patient has a mixed disorder of metabolic acidosis + respiratory acidosis or metabolic acidosis + respiratory alkalosis, you will need to be familiar with Winter’s formula.

Winter;s formula :
Expected pCo2 = {1.5(Hco3-) +8} +/-2

If your patient has metabolic acidosis, you expect him to breathe fast and wash out the Co2 so as to maintain the pH in normal limits …this is called “Compensation”. Compensation brings the serum pH towards the normal but never makes it completely normal – so, if you are seeing a normal pH in a metabolic acidosis , you can right away say that you are dealing with a Mixed disorder rather than a compensation alone.
The expected Pco2 in the above formula is the one that is expected as a comprnsation if your patient has low bicarbonate or metabolic acidosis. You need to compare this expected Pco2 with the real value of Pco2 obtained on the arterial blood gases ( measured Pco2).
Pearls for answering questions on Mixed Disorders:
A) If measured Pco2 is lower than the expected Pco2, that means your patient is washing out more C02 than expected —meaning, he has respiratory alkalosis co-existent with metabolic acidosis ( one example of such mixed disorder is Salicylate toxicity) .
B) If measured Pco2 is higher than expected Pco2, that means your patient is retaining Co2 which means he has a co-existent Respiratory acidosis along with metabolic acidosis ( eg: Cardiac arrest can cause such mixed acidosis because reduced respiratory drive causes CO2 retention leading to respiratory acidosis where as shock because of cardiac arrest causes lactic acidosis which is metabolic acidosis).
eg: If Hc03 – is 16, the expected PCo2 as per Winter;s formula should range between 30 to 34 ( see the above formula). However, let us say your patients Pco2 on the arterial blood gas is 20 –> you can call this metabolic acidosis + respiratory alkalosis. eg : Salicylate Toxicity
If Hc03 – is 16, the expected PCo2 as per Winter;s formula should range between 30 to 34 ( see the above formula). However, let us say your patients Pco2 on the arterial blood gas is 44 –> you can call this metabolic acidosis + respiratory acidosis. eg : Cardiac arrest
 
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* Re:Type 1 vs type 2 renal tubular acidosis
#2339302
  anona - 02/25/11 01:45
 
  yes, i noticed that MTB error too. They interchanged/ mislabled type 1 for type 2.

its a great book, but oh so many errors!!
 
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* Re:Type 1 vs type 2 renal tubular acidosis
#2339314
  door2success - 02/25/11 02:12
 
  but i guess in type 2 urine ph will be initially high due to excretion of bicarb and then later when bicarb levels begin to go down the urine ph becomes low.so i dont think its an error.correct me if am wrong  
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* Re:Type 1 vs type 2 renal tubular acidosis
#2339315
  depth - 02/25/11 02:13
 
  Is there a way to remember the causes?  
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* Re:Type 1 vs type 2 renal tubular acidosis
#2339737
  anona - 02/25/11 15:08
 
  on page 246 of MTB they wrote TYPE 1 as proximal, and type II as distal. then in the table that follows the description on page 247, type 1 is labelled as distal, type ii as proximal.
i think the table is correct, and was just a typographical error.

similarly, there are 2 versions of mtb. i read the book from cover to cover with a SP i found on the forum and we found out that there were differences in our books. like the sample case scenarios in psych were different. small diffrences but its nowhere on the book which is the first edition.
 
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* Re:Type 1 vs type 2 renal tubular acidosis
#2340312
  misshyd - 02/26/11 13:19
 
  anona; type 1 is distal and type ii is proximal. MTB has lot of errors  
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* Re:Type 1 vs type 2 renal tubular acidosis
#2340315
  misshyd - 02/26/11 13:22
 
  door2success, yes urine ph will be initially higher than 5.5 in Type II. Only when serum HCO3 falls to less than 16, urine PH starts falling below 5.5
Just remember this sentence : Proximal tubular acidosis is not as bad as DTA because PTA still retains its ability to acidify the urine once serum has been made significantly acidic i.e; hco3 less than 16 ( from dr.red nephro)
 
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* Re:Type 1 vs type 2 renal tubular acidosis
#3292830
  jublee - 05/06/16 23:56
 
  good explanation misshyd on RTA  
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