The Questions
For each patient with hypokalemic metabolic alkalosis described below, select the most likely cause of the electrolyte disorder (A-E).
A. Diuretic use
B. Surreptitious vomiting
C. Hypokalemic periodic paralysis
D. Gitelman syndrome
E. Conn syndrome
1. 16-year-old girl with amenorrhea, body mass index of 13, and a urine chloride concentration of 5 mEq/L.
2. 35-year-old man presenting for the first time with new-onset hypertension.
3. 32-year-old woman with a history of bulimia. Random urine chloride concentrations on three separate clinic visits were 10, 67 and 25 mEq/L.
4. 15-year-old girl with recurrent episodes of muscle weakness since childhood and a urine chloride concentration of 65 mEq/L. Her brother has had similar symptoms.
5. 20-year-old man with thyrotoxicosis and recurrent episodes of muscle weakness after meals.
The answers to the electrolyte quiz from May 15, 2012 are: 1. B, 2. E, 3. A, 4. D, 5. C.
Explanation
Hypokalemic metabolic alkalosis associated with hypertension, as in the 35-year-old man, suggests a state of hyperaldosteronism, such as Conn syndrome, renal artery stenosis, Cushing or Liddle syndrome. In patients without hypertension, the cause is usually either gastric loss of chloride from vomiting, or renal loss due to impaired sodium chloride absorption in the thick ascending loop of Henle (loop diuretics or Bartter syndrome) or distal convoluted tubule (thiazide diuretics or Gitelman syndrome). The urine chloride is particularly helpful as it is low (< 20 mEq/L) in response to gastrointestinal chloride loss with volume contraction, and high (> 40 mEq/L) when the cause of the volume contraction is inhibition of renal tubular sodium chloride reabsorption. Thus, in the two females with histories suggestive of eating disorders, the 16-yearold has a low urine chloride and likely vomits surreptitiously, while the 32-year-old has an intermittently high urine chloride suggesting intermittent diuretic abuse. The 15-year-old girl also has a high urine chloride, but the history of symptoms dating back to childhood, and the positive family history, suggest a familial disorder; Gitelman’s tends to present in this age group, while Bartter’s is usually more severe and presents in infancy or early childhood. Occasionally, hypokalemia is due to shift into the intracellular compartment. This occurs episodically in hypokalemic periodic paralysis, often precipitated by stress, exercise or a high carbohydrate meal, and may be inherited or acquired, the latter particularly in Chinese males with thyrotoxicosis, as in the case of the 20-year-old man.
(Questions and Answers courtesy of Dr. Alan Yu, Professor of Medicine and Director, The Kidney Institute, University of Kansas, KS, USA)
For each patient with hypokalemic metabolic alkalosis described below, select the most likely cause of the electrolyte disorder (A-E).
A. Diuretic use
B. Surreptitious vomiting
C. Hypokalemic periodic paralysis
D. Gitelman syndrome
E. Conn syndrome
1. 16-year-old girl with amenorrhea, body mass index of 13, and a urine chloride concentration of 5 mEq/L.
2. 35-year-old man presenting for the first time with new-onset hypertension.
3. 32-year-old woman with a history of bulimia. Random urine chloride concentrations on three separate clinic visits were 10, 67 and 25 mEq/L.
4. 15-year-old girl with recurrent episodes of muscle weakness since childhood and a urine chloride concentration of 65 mEq/L. Her brother has had similar symptoms.
5. 20-year-old man with thyrotoxicosis and recurrent episodes of muscle weakness after meals.
The answers to the electrolyte quiz from May 15, 2012 are: 1. B, 2. E, 3. A, 4. D, 5. C.
Explanation
Hypokalemic metabolic alkalosis associated with hypertension, as in the 35-year-old man, suggests a state of hyperaldosteronism, such as Conn syndrome, renal artery stenosis, Cushing or Liddle syndrome. In patients without hypertension, the cause is usually either gastric loss of chloride from vomiting, or renal loss due to impaired sodium chloride absorption in the thick ascending loop of Henle (loop diuretics or Bartter syndrome) or distal convoluted tubule (thiazide diuretics or Gitelman syndrome). The urine chloride is particularly helpful as it is low (< 20 mEq/L) in response to gastrointestinal chloride loss with volume contraction, and high (> 40 mEq/L) when the cause of the volume contraction is inhibition of renal tubular sodium chloride reabsorption. Thus, in the two females with histories suggestive of eating disorders, the 16-yearold has a low urine chloride and likely vomits surreptitiously, while the 32-year-old has an intermittently high urine chloride suggesting intermittent diuretic abuse. The 15-year-old girl also has a high urine chloride, but the history of symptoms dating back to childhood, and the positive family history, suggest a familial disorder; Gitelman’s tends to present in this age group, while Bartter’s is usually more severe and presents in infancy or early childhood. Occasionally, hypokalemia is due to shift into the intracellular compartment. This occurs episodically in hypokalemic periodic paralysis, often precipitated by stress, exercise or a high carbohydrate meal, and may be inherited or acquired, the latter particularly in Chinese males with thyrotoxicosis, as in the case of the 20-year-old man.
(Questions and Answers courtesy of Dr. Alan Yu, Professor of Medicine and Director, The Kidney Institute, University of Kansas, KS, USA)
I'm not a doctor, so it was impossible for me to pass this quiz. But it's clear, that it's better not to be ignorant in these questions!
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