Vancouver IM LMR

Senior IM residents Adam Kramer, Shamon Ahmed, and Fahad Alajmi presented a case during noon rounds on secondary hypertension. This was a great review of a practical approach to hypokalemia and workup of primary hyperaldosteronism.

See the presentation slide deck here.

Key takeaway points:

• Approach to hypokalemia:
  • Low intake/ shifting
  • Extrarenal losses: urine K < 20, urine K:Cr < 2
  • Renal loss: urine K > 20, urine K:Cr > 2
    • Osmotic diuresis
    • Metabolic acidosis
      • Type 1 & 2 RTA
    • Metabolic alkalosis
      • Hypertensive
        • Low renin/ low aldo: Cushing’s, Liddle’s syndrome, exogenous steroids or fludrocortisone, ++licorice
        • High renin/ high aldo: Secondary hyperaldosteronism e.g. renal artery stenosis, reninoma
        • Low renin/ high aldo: Primary hyperaldosteronism
      • Normo/hypotensive
        • Urine Cl > 20: Bartter, Gitelman, or diuretic use
        • Urine Cl < 20: recent/ intermittent diuretics or loss of gastric secretions
• Primary hyperaldosteronism
  • Most common secondary cause of hypertension (20% prevalence among those with resistant hypertension)
  • Characteristically presents with hypertension, hypokalemia (but not always!), metabolic alkalosis, and on testing high ARR (aldo to renin ratio i.e. high aldo, low-normal renin)
  • Workup:
    • Screening test: ARR
      • Must be done in morning while seated and OFF any MRAs e.g. spironolactone
    • Confirmatory test:
      • If ARR > 1400pmol/L/ng/mL/h or > 270pmol/L/ng/L and plasma aldosterone is > 440pmol/L, primary hyperaldosteronism is confirmed
      • If not, then need saline loading test or captopril suppression test (or can jump right to imaging)
    • Subtype testing:
      • CTA/ MRA to localize adrenal lesion
      • Selective adrenal venous sampling to determine unilateral vs bilateral
  • Treatment:
    • MRA for bilateral adrenal disease
    • Surgical adrenalectomy if unilateral