Renal Question

[kaleerkalut]

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Hi everyone,

Kaplan Qbank question QID# OL1342.seq states that the distal convoluted tubule is the location with the lowest level of hyptonicity. However, the Kaplan Renal Videos state that the the cortical collecting ducts continue to reabsorb a little bit more making it even more hypotonic.

I chose cortical collecting duct as the answer but distal convoluted tubule is right. Can somebody please clear this up? Thanks 🙂

 

[Syncity]

Hi everyone,

Kaplan Qbank question QID# OL1342.seq states that the distal convoluted tubule is the location with the lowest level of hyptonicity. However, the Kaplan Renal Videos state that the the cortical collecting ducts continue to reabsorb a little bit more making it even more hypotonic.

I chose cortical collecting duct as the answer but distal convoluted tubule is right. Can somebody please clear this up? Thanks 🙂

Just remember that the tonicity of the cortical collecting duct is variable. For example, in a water deprived individual with high serum ADH how could the collecting duct possibly be the most hypotonic?

 

[kaleerkalut]

Just remember that the tonicity of the cortical collecting duct is variable. For example, in a water deprived individual with high serum ADH how could the collecting duct possibly be the most hypotonic?

Because Aquaporins are instered in the distal collecting duct? Not sure.

 

[Chirurg]

the best answer is early distal tubule (if not in the answer choice, you pick fluid leaving loop of henle).

@kaleerkalut
if you go back to that section of the kaplan videos (chapter 4 b, Loop of Henle), you will realize you misunderstood Professor Dunn who said the following: If it is mentioned that there is no effect of ADH, then Collecting Duct is the right choice. (about)


hope this was of help and thanks for bringing this up as a refresher!

 

[kaleerkalut]

the best answer is early distal tubule (if not in the answer choice, you pick fluid leaving loop of henle).

@kaleerkalut
if you go back to that section of the kaplan videos (chapter 4 b, Loop of Henle), you will realize you misunderstood Professor Dunn who said the following: If it is mentioned that there is no effect of ADH, then Collecting Duct is the right choice. (about)


hope this was of help and thanks for bringing this up as a refresher!

I'll check it out but I think you are right. Thanks for your input 🙂

 

[kaleerkalut]

the best answer is early distal tubule (if not in the answer choice, you pick fluid leaving loop of henle).

@kaleerkalut
if you go back to that section of the kaplan videos (chapter 4 b, Loop of Henle), you will realize you misunderstood Professor Dunn who said the following: If it is mentioned that there is no effect of ADH, then Collecting Duct is the right choice. (about)


hope this was of help and thanks for bringing this up as a refresher!

Do you happen to remember why thiazides can help with nephrogenic diabetes insipidus? I just watched the Pharm video with Raymon but I can't seem to make it stick. Thanks in advance.

 

[Chirurg]

Do you happen to remember why thiazides can help with nephrogenic diabetes insipidus? I just watched the Pharm video with Raymon but I can't seem to make it stick. Thanks in advance.

The mechanism is not fully understood.
I always found that paradox to give a diuretic to someone with polyuria, but the theory goes, if you volume deplete someone with thiazides his GFR decreases, PCT has more time to reabsorb electrolytes and water --> his nephrogenic diabetes insipidus won't be that bad.
but it has also been proven that this can not be the sole mechanism of action...

 

[Torquer]

Regarding the point about DCT and hypotonicity, the DCT is actually referred to as the DILUTING segment because it actively absorbs Na and Cl (also Ca under the influence of PTH) - hence making urine hypotonic.
As above posts also mentioned, the CCT can further absorb more ions and make the urine hypotonic, BUT they are hormone dependant.
Hope that helps!
Remember, D for Dct, D for Diluting segment.

Source: First Aid 2011 - somewhere in a the first few pages of the renal chapter.