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Bartter
syndrome is a constellation of fluid, electrolyte, and hormonal
abnormalities characterized by renal K, Na, and Cl wasting; hypokalemia;
hyperaldosteronism; hyperreninemia; and normal BP. The
condition affects children, producing electrolyte and growth abnormalities.
Diagnosis is assisted by urine electrolyte measurements and hormone assays
but is typically a diagnosis of exclusion. Treatment consists of
NSAIDs, K-sparing diuretics, low-dose ACE inhibitors, and electrolyte
replacement.
Bartter syndrome results from deranged NaCl transport in the ascending thick limb of the loop of Henle and the distal tubule. Subsequent K, Na, and Cl wasting leads to increased renin and aldosterone release, metabolic alkalosis, hyperuricemia, hypomagnesemia, hypercalciuria, and increased prostaglandin secretion. Further, Na wasting results in a chronically low plasma volume reflected by a normal BP despite high renin and angiotensin levels.
Bartter syndrome usually appears in childhood as a sporadic or familial disorder (usually autosomal recessive).
Symptoms and Signs
Bartter syndrome can manifest antenatally with intrauterine growth restriction and polyhydramnios. After birth, affected children have poor growth rates and appear malnourished. Most patients have low or low-normal BP and may have signs of volume depletion. Inability to retain K, Ca, or Mg can lead to muscle weakness, spasms, tetany, or palpitations. Polydipsia, polyuria, and vomiting may also be present. Mental retardation and nephrocalcinosis sometimes result.
Diagnosis
Bartter syndrome is typically a diagnosis of exclusion but should be suspected in children with an unexplained constellation of symptoms as described above. Measurement of urine electrolytes demonstrates high levels of Na, K, and Cl that are inappropriate for the euvolemic or hypovolemic state of the patient. Plasma levels of renin and aldosterone are increased, and the absence of hypertension and edema can distinguish the disorder from primary and secondary aldosteronism (see Adrenal Disorders:Primary Aldosteronism for Table Table 3: Adrenal Disorders: Differential Diagnosis of Aldosteronism).
In adult patients, bulimia nervosa, vomiting, and surreptitious laxative abuse must be excluded as causes. In these conditions, the urinary Cl is usually low (< 20 mmol/L). Diuretic abuse can also mimic this condition and can only be confirmed by a urine assay for diuretics.
Definitive diagnosis is through genetic testing, which is not commercially available and thus is rarely performed.
Prognosis
and Treatment
Bartter syndrome may result in premature birth and severe electrolyte disorders and symptoms but does not typically lead to chronic renal insufficiency.
The combination of NSAIDs ( indomethacin , 1 to 2 mg/kg po once/day) and a K-sparing diuretic ( spironolactone , 150 mg po bid, or amiloride , 10 to 20 mg po bid) corrects most features. Further improvement in plasma electrolytes can be gained with low-dose ACE inhibitors. However, no therapy can completely eliminate K wasting, and K supplementation (KCl 20 to 40 mEq po once/day or bid) is often necessary. Mg and Ca supplements may also be needed.
Exogenous growth hormone is sometimes used to treat short stature in affected children.
Last full review/revision November 2005
Content last modified November 2005
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