Makindo Medical Notes

Bartter's syndrome is a rare inherited disorder characterized by defective kidney function, leading to significant electrolyte imbalances. It is associated with hypokalaemia, though hypertension is notably absent, which differentiates it from other kidney-related disorders.

About

• Characterized by low potassium (hypokalaemia).
• Normal or low blood pressure.
• Often mimics the effects of the diuretic Furosemide (Lasix in the US).

Aetiology

• Defects in three tubular transport proteins have been identified.
• The most common defect affects the Na-K-Cl co-transporter in the thick ascending limb of the loop of Henle.
• This leads to impaired Na⁺ and Cl⁻ reabsorption, which results in:
• Increased excretion of potassium (K⁺) and hydrogen ions (H⁺), causing hypokalaemia and metabolic alkalosis.
• Increased production of prostaglandins, which contribute to electrolyte imbalances.
• Hyperplasia of the juxtaglomerular apparatus (JGA), leading to elevated levels of renin and aldosterone.

Clinical Features

• Infants present with signs of tiredness and lethargy due to low potassium levels.
• Failure to thrive is common in children.
• Muscle weakness, fatigue, and constipation due to electrolyte disturbances.
• Normal or low blood pressure, unlike other hyperaldosteronism conditions, which typically present with high blood pressure.
• May present as a rare cause of growth failure in childhood or adolescence.

Investigations

• Elevated levels of renin and aldosterone.
• Hypokalaemic metabolic alkalosis (low potassium and elevated blood pH).
• Hypocalcaemia (low calcium) and hypercalciuria (excess calcium in urine).
• Defective Na/K/Cl co-transporter in the thick ascending limb of the loop of Henle.
• Normal or low blood pressure.

Differential Diagnosis

• Chronic vomiting or diarrhoea.
• Diuretic abuse.
• Magnesium deficiency.
• Gitelman syndrome (another renal tubular disorder but with hypomagnesemia).

Management

• Supplementation of sodium (Na) and potassium (K) to address electrolyte imbalances.
• Use of potassium-sparing diuretics, such as Spironolactone or Amiloride, to reduce potassium loss.
• Administration of NSAIDs (e.g., Indomethacin) to reduce prostaglandin production.
• Consider ACE inhibitors or angiotensin receptor blockers (ARBs) to reduce renin and aldosterone levels if necessary.