Is a young patient with severe hypokalemia, hypomagnesemia, and a history of recurrent kidney stones likely to have Bartter syndrome?

Diagnostic Assessment for Bartter Syndrome

Yes, this patient is highly likely to have Bartter syndrome, specifically Type 1 or Type 2, given the constellation of severe hypokalemia, hypomagnesemia, and recurrent kidney stones—the latter indicating hypercalciuria and likely nephrocalcinosis, which are pathognomonic features of these early-onset Bartter subtypes. 1, 2

Key Diagnostic Features Supporting Bartter Syndrome

The clinical triad presented strongly suggests Bartter syndrome rather than other salt-losing tubulopathies:

• Severe hypokalemia results from impaired salt reabsorption in the thick ascending limb of Henle's loop, leading to increased distal sodium delivery and aldosterone-mediated potassium secretion 1, 2

• Hypomagnesemia in the context of kidney stones points toward Bartter syndrome, as this combination with hypercalciuria distinguishes it from Gitelman syndrome (which presents with hypomagnesemia but hypocalciuria) 1, 3

• Recurrent kidney stones indicate hypercalciuria and likely nephrocalcinosis, which are typical for Bartter syndrome Types 1 and 2 but not seen in Gitelman syndrome 1, 2

Critical Distinguishing Features from Gitelman Syndrome

The presence of kidney stones is the decisive clinical feature:

• Bartter syndrome causes hypercalciuria due to the association between sodium and calcium reabsorption in the loop of Henle—when salt reabsorption is impaired, calcium excretion increases 1, 3

• Gitelman syndrome presents with hypocalciuria (not hypercalciuria), making kidney stones extremely unlikely 3, 4

• Measuring urinary calcium excretion easily differentiates these conditions: fractional calcium excretion is elevated in Bartter syndrome and reduced in Gitelman syndrome 1, 2, 3

Recommended Diagnostic Workup

Immediate laboratory assessment should include:

• Serum electrolytes with specific attention to chloride (hypochloremic metabolic alkalosis expected) 1, 2

• Serum magnesium and ionized calcium levels 2

• Fractional excretion of chloride (typically >0.5% in Bartter syndrome) 1, 2

• Urinary calcium-creatinine ratio to confirm hypercalciuria (distinguishes Type 1 or 2 from other types) 1, 2

• Renin and aldosterone levels (hyperreninemic hyperaldosteronism is characteristic) 1, 2

• Renal ultrasound to detect nephrocalcinosis, which is typical in Types 1 and 2 1, 2

Genetic confirmation:

• Gene panel testing should be offered with focus on SLC12A1 (Type 1) and KCNJ1 (Type 2), which have 90-100% analytical sensitivity in children 2, 4

• Genetic testing confirms the diagnosis and guides long-term management and family counseling 1, 2

Common Diagnostic Pitfalls

Do not confuse with Gitelman syndrome based solely on hypomagnesemia:

• Both conditions cause hypomagnesemia, but urinary calcium excretion is the key differentiator 3

• Gitelman syndrome typically presents later (adolescence or adulthood) with milder symptoms, whereas Bartter Types 1 and 2 often present with severe neonatal or early childhood manifestations 1

Recognize that kidney stones in a young patient with hypokalemia should immediately raise suspicion for Bartter syndrome:

• Young age at onset of kidney stone disease warrants investigation for specific underlying causes, including Bartter syndrome 1

• The combination of salt-wasting tubulopathy with nephrocalcinosis is virtually diagnostic of Bartter syndrome Types 1 or 2 1, 2