Bartter syndrome is a rare inherited kidney disorder in which the kidneys cannot properly reabsorb salt. Instead of recycling sodium and chloride back into the bloodstream, the kidneys flush them out in urine, dragging water, potassium, calcium, and other essential minerals along with them. The result is a cascade of electrolyte imbalances that can affect growth, bone strength, muscle function, and long-term kidney health.
How the Kidneys Lose Salt
In a healthy kidney, a structure called the loop of Henle acts like a recycling plant. As fluid passes through its thick ascending limb, specialized transport channels pull sodium, potassium, and chloride back into the body. In Bartter syndrome, genetic mutations disable one or more of these channels. Salt passes straight through and into the urine.
That initial salt loss triggers a chain reaction. When extra sodium reaches the lower sections of the kidney’s filtering tubes, the body tries to salvage it by swapping it for potassium and hydrogen ions. This trade-off pushes potassium levels in the blood dangerously low (hypokalemia) and shifts the blood toward an overly alkaline state called metabolic alkalosis. On top of that, the broken salt transport disrupts the electrical gradient the kidney uses to reclaim calcium and magnesium, so those minerals get flushed out too. The net effect: dehydration, low potassium, low chloride, excess calcium in the urine, and blood pressure that stays low or normal despite the body’s attempts to compensate.
Types and Inheritance
Bartter syndrome follows an autosomal recessive pattern, meaning a child must inherit a faulty copy of the responsible gene from each parent. Several different genes can cause the condition, which is why clinicians classify it into subtypes (types I through V). Each type involves a different transport channel in the loop of Henle, but they all produce the same core problem: the kidney cannot hold onto salt.
The type matters most for predicting when symptoms appear and how severe they are. Types I and II tend to cause the most dramatic form, known as antenatal Bartter syndrome, which shows up before birth. Type III typically causes the “classic” childhood form. Type V is unusual in that it follows an autosomal dominant pattern and involves the calcium-sensing receptor, producing low blood calcium and high urinary calcium alongside the typical salt-wasting picture.
Symptoms Before and After Birth
The antenatal form can make itself known during pregnancy. The affected fetus produces so much urine that amniotic fluid builds up excessively, a condition called polyhydramnios. This often appears in the second trimester with no associated birth defects to explain it, and it frequently triggers preterm labor. After delivery, the newborn may show dangerously low sodium and potassium, along with elevated levels of renin and aldosterone as the body desperately tries to conserve salt.
In the classic childhood form, symptoms develop more gradually. Parents may notice that their child drinks and urinates far more than expected. Growth falters early. Affected children often fail to gain weight at the expected rate, a pattern sometimes called failure to thrive. In a Korean multicenter study that followed 54 patients for an average of eight years, 41% still had short stature (below the 3rd percentile for height) at their last checkup, despite ongoing treatment. Other common symptoms include muscle weakness, cramping, fatigue, constipation, and chronic dehydration.
Bone, Kidney, and Hearing Complications
Because the kidneys dump calcium into the urine, two things happen over time. First, bones weaken. The chronic calcium loss can lead to reduced bone density (osteopenia), making fractures more likely. Second, the excess calcium can crystallize inside the kidney tissue itself, a process called nephrocalcinosis, which gradually hardens and damages the organ.
Kidney function holds up for many patients, but not all. In the same Korean cohort, 11% developed moderate to severe chronic kidney disease over the follow-up period. Literature reviews report that figure can range anywhere from 0% to 64% depending on the subtype and study population, with type III carrying a notably higher risk. In rare cases, affected children also develop sensorineural hearing loss caused by abnormalities in the inner ear, particularly in certain antenatal subtypes where the mutated channel is expressed in both the kidney and the cochlea.
How It Differs From Gitelman Syndrome
Gitelman syndrome is the condition most commonly confused with Bartter syndrome. Both cause low potassium, metabolic alkalosis, and salt wasting. The key differences come down to calcium and magnesium. In Bartter syndrome, urinary calcium is normal or high, and magnesium may occasionally dip. In Gitelman syndrome, urinary calcium is distinctly low, and blood magnesium is almost always low. Gitelman syndrome also tends to present later, often in adolescence or adulthood, and runs a milder course. Nephrocalcinosis is absent in Gitelman syndrome, while it can develop in Bartter syndrome. Prostaglandin levels in the urine are typically elevated in classic Bartter syndrome but stay normal in Gitelman syndrome.
Treatment and What to Expect
There is no cure for Bartter syndrome. Treatment focuses on replacing what the kidneys waste and slowing the loss. Potassium and magnesium supplements form the backbone of management, often in large doses because the kidneys keep flushing these minerals out. Sodium chloride supplementation helps counter the ongoing salt deficit, and adequate hydration is essential given the constant water loss.
The other major treatment target is prostaglandins. The kidneys overproduce these inflammatory signaling molecules in response to the salt-wasting defect, and that overproduction worsens the cycle of fluid and electrolyte loss. Anti-inflammatory medications that block prostaglandin production have been a mainstay of therapy for decades. These drugs can improve growth, reduce urinary losses, and help normalize electrolyte levels, but they require careful monitoring because of potential side effects on the stomach, kidneys, and blood cells. Newer, more targeted anti-inflammatory options have been explored in small studies to reduce that side-effect burden.
With consistent treatment, many children see meaningful improvements in growth velocity and fewer episodes of dangerous electrolyte drops. Still, lifelong monitoring of kidney function, electrolytes, and bone health is part of the reality of living with this condition. The goal is to keep potassium in a safe range, protect the kidneys from calcium deposits, and support normal development as much as the underlying defect allows.