What is the diagnosis for an elderly female patient with hypernatremia and hypokalemia?

Diagnosis: Primary Hyperaldosteronism (Conn's Syndrome)

This elderly female patient with a sodium level of 145 mEq/L (high-normal to mildly elevated) and potassium of 3.4 mEq/L (hypokalemia) most likely has primary hyperaldosteronism, particularly given the combination of hypernatremia with hypokalemia in the absence of diuretic use. 1

Key Diagnostic Considerations

Electrolyte Pattern Analysis

The combination of elevated/high-normal sodium with hypokalemia creates a specific diagnostic pattern:

• Hypernatremia with hypokalemia is characteristic of mineralocorticoid excess states, particularly primary hyperaldosteronism 1
• This electrolyte pattern (hypernatremia, hypokalemia, and metabolic alkalosis when present) strongly suggests excess aldosterone activity 1
• Primary aldosteronism has a prevalence of approximately 20% in patients with resistant hypertension 2

Critical Next Steps

Immediate laboratory evaluation should include:

• Urine potassium excretion: A urinary potassium excretion of ≥20 mEq/day in the presence of serum potassium <3.5 mEq/L indicates inappropriate renal potassium wasting 3
• Plasma aldosterone concentration (PAC) and plasma renin activity (PRA) to calculate the aldosterone-to-renin ratio 2
• Serum magnesium: Hypokalemia often coexists with hypomagnesemia and may require magnesium supplementation for effective potassium repletion 2
• Blood pressure measurement: Secondary hypertension, particularly in elderly patients with new-onset or difficult-to-control hypertension, should raise suspicion 2, 1

Differential Diagnosis to Consider

Other causes of this electrolyte pattern include:

• Diuretic use (thiazides or loop diuretics): Most common cause of hypokalemia in clinical practice, with thiazides independently associated with both hyponatremia and hypokalemia 4, 5
• Bartter syndrome: Presents with hypokalemia and metabolic alkalosis, though typically diagnosed earlier in life 2
• Excessive mineralocorticoid activity from other sources (adrenal adenoma, bilateral adrenal hyperplasia, or rarely adrenal carcinoma) 1
• Gastrointestinal losses: Though these typically present with hypovolemia and would show urine sodium <20 mmol/L 6

Management Approach

Immediate Treatment

Potassium replacement should be initiated:

• Use potassium chloride specifically, not potassium citrate or other salts, as chloride replacement is essential when metabolic alkalosis is present 2, 3
• Target serum potassium to 4.0-5.0 mEq/L range, as even modest hypokalemia increases risks of arrhythmias and sudden death 2
• Magnesium supplementation may be necessary, as hypokalemia refractory to potassium replacement often indicates concurrent magnesium deficiency 2

Medication Review

Critical medication assessment:

• Discontinue or avoid: NSAIDs, which can worsen electrolyte abnormalities 2
• Review diuretic use: If the patient is on thiazide or loop diuretics, these are the most likely culprits 4, 5
• Avoid ACE inhibitors/ARBs initially until hyperaldosteronism is ruled out, as these can cause hyperkalemia in the setting of renal impairment 2

Diagnostic Workup

If primary hyperaldosteronism is confirmed:

• Adrenal imaging (CT or MRI) to identify unilateral adenoma vs. bilateral hyperplasia 2, 1
• Adrenal vein sampling may be needed to lateralize aldosterone production if surgical intervention is considered 2
• Unilateral adrenalectomy is curative for aldosterone-producing adenomas 2
• Bilateral disease requires medical management with mineralocorticoid receptor antagonists 2

Common Pitfalls to Avoid

• Do not assume age-related changes: New-onset hypertension with electrolyte abnormalities in elderly patients warrants full secondary hypertension workup 2, 1
• Do not use potassium citrate: This worsens metabolic alkalosis; always use potassium chloride 2, 3
• Do not overlook magnesium: Hypokalemia may be refractory to treatment without concurrent magnesium repletion 2
• Monitor closely: Serum electrolytes and renal function require frequent monitoring during treatment 2