Bartter vs Gitelman Syndrome: How to Tell Them Apart
Bartter and Gitelman are inherited salt-wasting tubulopathies that both produce hypokalemia, metabolic alkalosis, and secondary hyperaldosteronism with normal-to-low blood pressure. The core axis that separates them is urine calcium: Bartter (a thick ascending limb defect, mimicking loop diuretics) causes hypercalciuria, while Gitelman (a distal convoluted tubule defect, mimicking thiazides) causes hypocalciuria. Age of onset, severity, and magnesium status track along the same tubular logic.
How to tell them apart
| Feature | Bartter Syndrome | Gitelman Syndrome |
|---|---|---|
| Urine calcium (KEY DIFFERENTIATOR) | High — hypercalciuria | Low — hypocalciuria |
| Tubular location | Thick ascending limb of the loop of Henle (TAL) | Distal convoluted tubule (DCT) |
| Diuretic equivalent | Genetic equivalent of chronic loop diuretic (furosemide) use | Genetic equivalent of chronic thiazide (HCTZ) use |
| Age of onset | Infancy/childhood | Adolescence/adulthood |
| Severity | More severe, often with failure to thrive | Milder, with muscle cramps and fatigue |
| Nephrocalcinosis risk | Yes — hypercalciuria predisposes; monitor closely | No |
| Magnesium status | Typically normal or only mildly low | Consistently and often severely low (hypomagnesemia is a defining feature), frequently requiring aggressive replacement |
| Role of NSAIDs (prostaglandin inhibition) | Indomethacin is a hallmark therapy — the TAL defect drives elevated renal prostaglandin E2 that NSAIDs blunt | Not a standard therapy — prostaglandin overproduction is not a defining feature |
| Affected transporter | NKCC2, ROMK, ClC-Kb, or Barttin in the TAL | NCC (Na-Cl cotransporter) in the DCT |
The reasoning
Start by recognizing the shared picture: a normotensive patient with hypokalemia and metabolic alkalosis, and a urine chloride >20 confirming ongoing renal salt wasting (excluding vomiting and remote diuretic use). Once you have anchored on a salt-wasting tubulopathy, arbitrate with urine calcium. High urine calcium points to Bartter — the TAL defect mimics a loop diuretic, which wastes calcium and risks nephrocalcinosis. Low urine calcium points to Gitelman — the DCT defect mimics a thiazide, which retains calcium. Reinforce with the clinical gestalt: a young child with failure to thrive fits Bartter, whereas an adolescent or adult with muscle cramps and profound hypomagnesemia fits Gitelman. Persistent, severe hypomagnesemia is a Gitelman-defining clue, and a favorable response to indomethacin supports Bartter.
Key tests
- Urine calcium: elevated in Bartter (hypercalciuria), low in Gitelman (hypocalciuria) — the single most useful discriminator
- Serum magnesium: often normal or only mildly low in Bartter, but consistently and often severely low in Gitelman
- Renal ultrasound: nephrocalcinosis may be seen in Bartter but is absent in Gitelman
- Basic metabolic panel: both show hypokalemia and elevated bicarbonate (metabolic alkalosis), so this confirms the shared syndrome but does not distinguish them
- Urine chloride: >20 mEq/L in both, confirming chloride-resistant renal salt wasting rather than vomiting or diuretic washout
What they share
- Hypokalemia from renal potassium wasting
- Metabolic alkalosis (chloride-resistant, urine chloride >20)
- Secondary hyperaldosteronism driven by volume depletion
- Normal to low blood pressure (never hypertensive)
- Salt wasting with volume depletion
- Managed with potassium and salt supplementation plus potassium-sparing diuretics
Pitfalls
- Forgetting that both cause hypokalemic metabolic alkalosis — do not use these shared features to distinguish them; only urine calcium and the associated tubular clues discriminate.
- Mislabeling either as hypertensive; both are normotensive to hypotensive because of salt wasting, unlike primary hyperaldosteronism or Liddle syndrome.
- Confusing which direction calcium goes: Bartter = HIGH urine calcium (loop-like), Gitelman = LOW urine calcium (thiazide-like).
- Assuming NSAIDs are used for both — indomethacin is a classic treatment for Bartter (driven by its high renal prostaglandin E2 production), not for Gitelman.
- Expecting profound hypomagnesemia in Bartter — magnesium is often normal or only mildly low in Bartter, whereas consistent, sometimes severe hypomagnesemia is a defining feature of Gitelman.
- Attributing chloride-resistant alkalosis to vomiting; vomiting gives a LOW urine chloride, whereas Bartter and Gitelman give a HIGH urine chloride.
- Assuming Gitelman is trivial because it is milder — its severe hypomagnesemia can drive dangerous cramps and arrhythmia risk, and hypokalemia stays refractory until magnesium is repleted.
Practice this the way the exam tests it — on branching cases where your decisions shape the patient.