Testing for Bartter Syndrome
If patients, especially dehydrated infants and young children, are found to have hypokalemia and a high serum bicarbonate concentration on routine labs and do not correct with potassium and chloride replacement treatment, consider possible renal tubular disorder.
- Serum Magnesium – Will be low in Gitelman’s Syndrome, May be low or normal in Bartter’s Syndrome
- Serum Potassium – Is usually low in all variants of Bartter’s.
- Serum Calcium – Normal – Low Values in all variants
- Comprehensive Metabolic Panel – Patient will show signs of Metabolic Alkalosis. Decreased Na+, K+, and Mg+
- Renin – Should see a increase in Renin although with Gitelman’s this may come back normal.
- Aldosterone – Should see elevated Aldosterone levels although with Gitelman’s this may be normal.
- Complete Thyroid Panel – Decreased or Increased thyroid function could mimick the symptoms of Bartter’s.
- A 24 hour urine should be done on all patients with suspected Bartter’s Syndrome.
- Initiate a timed urine for Potassium – In hypokalemia, normal kidneys retain potassium. Elevated urinary potassium levels with low blood potassium levels are abnormal and suggest the kidney is having problems retaining potassium.
- Initiate a timed urine for Aldosterone – Aldosterone levels should be low in volume-replete patients. If urinary aldosterone levels are high, despite volume replacement, there is an abnormal stimulation of aldosterone. If urinary aldosterone levels are high, despite volume replacement, there is an abnormal stimulation of aldosterone. Patients with primary hyperaldosteronism in a volume replete state, usually have normal-to-high blood pressure. Low or low normal blood pressure with high aldosterone excretion suggests the primary problem is something else, and the aldosterone response is secondary to the undiagnosed primary abnormality.
- A timed urine collection for chloride is next – Extrarenal volume depletion is a possible reason for low blood pressure, high aldosterone excretion and potassium loss. In this case, the kidneys retain sodium and chloride, and urinary chloride should be low. High urine chloride with low blood pressure, high aldosterone secretion and high urinary potassium levels are only found with long term diuretic use and Bartter’s or Gitelman’s syndrome. If diuretic use is considered a possibility, a urine screen for diuretics can be ordered. Otherwise, the diagnosis is Bartter’s or Gitelman’s syndrome.
- Mutations in four different transporters cause Bartter’s syndrome. Which of the four mutations can be determined in several ways.
- Analysis of the genes for the transporters show multiple problems leading to abnormal gene function, including missense mutations, frameshifts, loss of function mutations and large deletions
Urine Drug Screen
- Patients should be tested for diuretics and illicit drugs.
- Antenatal Bartter’s syndrome can best be diagnosed by ultrasonography. The fetus may have polyhydramnios and intrauterine growth retardation.
- After birth, especially if the disease is diagnosed in older subjects who have hypercalciuria, a renal ultrasound or flat plate of the abdomen for nephrocalcinosis should be considered.
- Sonographic finding include diffusely increased echogenicity, hyperechoic pyramids and interstitial calcium deposition.
- Since continued calcium loss may affect bones, DEXA (dual x-ray absorptiometry) for bone mineral density may also be reasonable in older patients.