A 28-year-old male presents with polyuria and polydipsia. Lately, he has been getting up at least six times during the night to urinate. He denies any past medical problems. He is currently on no medications. His family history is unremarkable. He migrated from India four years ago. He chews tobacco, but does not smoke. He denies alcohol use. Physical examination reveals a blood pressure of 160/94 mmHg. He weighs 165 pounds and is 5' 7" tall. The thyroid gland is normal to palpation. There is no abdominal bruit. The rest of the physical examination is unremarkable. His potassium level is 3.2 mEq/L. Hypokalemia is confirmed on repeat testing. What is the next best step in the evaluation of this patient?

Question

A 28-year-old male presents with polyuria and polydipsia.  Lately, he has been getting up at least six times  during the night to urinate.  He denies any past medical problems.  He is currently on no medications.  His family history is unremarkable.  He migrated from India four years ago.  He chews tobacco, but does not smoke.  He denies alcohol use.  Physical examination reveals a blood pressure of 160/94 mmHg.  He weighs 165 pounds and is 5' 7" tall.  The thyroid gland is normal to palpation.  There is no abdominal bruit.  The rest of the physical examination is unremarkable.  His potassium level is 3.2 mEq/L.  Hypokalemia is confirmed on repeat testing.  What is the next best step in the evaluation of this patient?

Quizplus · Accepted Answer

Explanation: The patient presents with hypertension and hypokalemia, which are characteristic of primary hyperaldosteronism (Conn's syndrome). His polyuria can be explained by the hypokalemic state, which causes an impaired urinary concentrating ability. The commonly used screening test involves the measurement of plasma aldosterone to plasma renin activity ratio, and a ratio of 30 or more is suggestive of excessive aldosterone secretion from the adrenal gland. Patients with excessive aldosterone secretion of the adrenal gland have suppressed renin activity and elevated levels of plasma aldosterone. Because many patients with essential hypertension have suppressed renin activity, aldosterone level over 15 ng/dl is required to interpret the test correctly. (Choice A) This patient does not have any clinical features of Cushing's syndrome. Therefore, 24-hour urinary cortisol levels would not be useful. Cushing's syndrome can sometimes cause hypokalemia due to the action of excessive glucocorticoid on the mineralocorticoid receptor. (Choice C) Deoxycorticosterone also has mineralocorticoid activity. Deoxycorticosterone levels can be useful in patients with hypokalemia and hypertension who have suppressed levels of both renin and aldosterone. Suppression of both renin and aldosterone suggests that some other mineralocorticoid like deoxycorticosterone is responsible for causing this mineralocorticoid excess syndrome. (Choice D) Secondary hyperaldosteronism is seen in patients with renal artery stenosis. One of the common causes of renal artery stenosis is fibromuscular dysplasia, which is predominantly seen in young females. Male sex and absence of abdominal bruit makes renal artery stenosis unlikely in the patient described in this vignette. (Choice E) Although a measurement of 24-hour urinary potassium level will demonstrate kaliuresis, this will not determine the cause of the patient's hypokalemia and hypertension. EducationalObjective: Patients with spontaneous hypokalemia and hypertension should be investigated for hyperaldosteronism. One of the best screening test for this disorder is measurement of plasma aldosterone to plasma renin activity (not renin levels) ratio.

A 28-Year-Old Male Presents with Polyuria and Polydipsia