Happy New Year to all MRCP Blog readers! May 2011 become the year for you to pass your MRCP Part 1 and 2!!
Friday, December 31, 2010
Friday, December 17, 2010
Liddle's syndrome in MRCP
Liddle's syndrome in MRCP
I must say that there are a few genetic renal transport disorders which are popular in MRCP part 1 and 2. These are Bartter's syndrome, Gitelman's syndrome and of course Liddle's syndrome.
Liddle's syndrome is one of the rare causes of secondary hypertension. For you to understand better, you must know that our body maintains fluid balance mainly by controlling sodium homeostasis. However about 25000 mmol of sodium is being filtrated from our kidney everyday and it is crucial that majority of the sodium is being reabsorped from the tubule.
Although collecting duct is only responsible for 1-2% of total sodium reabsorption, it is the major site for our body to control the fluid status because it is the only site that is sensitive to our body hormone ( aldosterone)
I must say that there are a few genetic renal transport disorders which are popular in MRCP part 1 and 2. These are Bartter's syndrome, Gitelman's syndrome and of course Liddle's syndrome.
Liddle's syndrome is one of the rare causes of secondary hypertension. For you to understand better, you must know that our body maintains fluid balance mainly by controlling sodium homeostasis. However about 25000 mmol of sodium is being filtrated from our kidney everyday and it is crucial that majority of the sodium is being reabsorped from the tubule.
Although collecting duct is only responsible for 1-2% of total sodium reabsorption, it is the major site for our body to control the fluid status because it is the only site that is sensitive to our body hormone ( aldosterone)
Sodium is mainly being reabsorped via Sodium channel ( ENAc) at collecting duct. When aldosterone binds to mineralcorticoid ( MR) receptor, more ENac will be synthesized and more sodium will be reabsorped and more pottasium being excreted ( that explaines why primary aldosteronism patients have hypertension and hypokalemia)
Liddle's syndrome is just a genetic disorder when the ENac is activated all the time and sodium reabsorption is enhanced leading to hypertension and hypokalemia.
Hypokalemia and Hypertension
Hypokalemia and Hypertension
We are always reminded that when a patient is diagnosed to have hypertension, the possibility of secondary hypertension must be entertained especially for young patients.
There are various clues that can lead us to suspect a patient might have secondary causes and one of them is hypokalemia.
Therefore, if you find a patient with hypertension and hypokalemia, always think of the following diagnosis,
1) Renal Artery stenosis or renin secreting tumor ( RAS)
2) Liddle's syndrome
3) Adrenal hyperfunction- can be due to adrenal ademona/carcinoma leading to hyperaldosteronism
4) Licorice usage or syndrome of apparent mineralcorticoid access ( SAME)
And one of the popular question in MRCP is how to differentiate these four conditions!!
It is quite easy if we know how renin angiotensin aldosterone ( RAA) system works. It is summarised as the following image,
We are always reminded that when a patient is diagnosed to have hypertension, the possibility of secondary hypertension must be entertained especially for young patients.
There are various clues that can lead us to suspect a patient might have secondary causes and one of them is hypokalemia.
Therefore, if you find a patient with hypertension and hypokalemia, always think of the following diagnosis,
1) Renal Artery stenosis or renin secreting tumor ( RAS)
2) Liddle's syndrome
3) Adrenal hyperfunction- can be due to adrenal ademona/carcinoma leading to hyperaldosteronism
4) Licorice usage or syndrome of apparent mineralcorticoid access ( SAME)
And one of the popular question in MRCP is how to differentiate these four conditions!!
It is quite easy if we know how renin angiotensin aldosterone ( RAA) system works. It is summarised as the following image,
For RAS or renin secreting tumour, you will have high renin and high aldosterone. For aldrenal hyperfunction, patients have high aldosterone level but normal renin.
As for Liddle's syndrome and SAME, I will try to explain a bit deeper next time!
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