American Board of Internal Medicine (ABIM) Certification Practice Exam

Bartter syndrome is known to mimic the effects of which category of diuretics?

1. Thiazide diuretics

2. Loop diuretics

3. Potassium-sparing diuretics

4. Carbonic anhydrase inhibitors

The correct answer is: Loop diuretics

Bartter syndrome is a genetic disorder that affects the kidneys and leads to a specific type of electrolyte imbalance and metabolic alkalosis, which closely resembles the effects of loop diuretics. Loop diuretics, such as furosemide, primarily work by inhibiting the sodium-potassium-chloride (Na+/K+/2Cl-) co-transporter in the thick ascending limb of the loop of Henle, resulting in increased excretion of sodium, chloride, and potassium. In Bartter syndrome, there is a similar disruption of electrolyte reabsorption in the thick ascending limb of the loop of Henle, causing a loss of sodium, chloride, and often potassium. As a result, patients with Bartter syndrome typically experience hypokalemic metabolic alkalosis, which mirrors the effects seen in individuals taking loop diuretics. The distinction lies in the underlying mechanisms; while loop diuretics induce these effects through pharmacological action, Bartter syndrome does so due to genetic defects affecting the renal tubular function. The resultant clinical picture, including electrolyte imbalances, resembles the effects produced by loop diuretics, solidifying the connection between Bartter syndrome and this category of diuretic.