American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the main characteristic of renal syndromes such as Bartter and Gitelman when they are mimicked by diuretics?

1. Decreased glomerular filtration rate

2. Electrolyte imbalances

3. Increased protein catabolism

4. Fluid retention

The correct answer is: Electrolyte imbalances

The main characteristic of renal syndromes like Bartter and Gitelman when they are mimicked by diuretics is primarily related to electrolyte imbalances. Both Bartter syndrome and Gitelman syndrome are inherited disorders affecting renal tubule function, leading to significant disturbances in electrolyte homeostasis. Bartter syndrome, typically associated with defects in the renal loop of Henle, results in hypokalemia (low potassium), metabolic alkalosis, and hypovolemia, primarily due to impaired sodium reabsorption. Gitelman syndrome, on the other hand, predominantly affects the distal convoluted tubule, leading to similar electrolyte imbalances including hypomagnesemia (low magnesium), hypokalemia, and metabolic alkalosis as well. When diuretics are used, they induce a state that closely resembles these syndromes by promoting similar electrolyte disturbances. For example, loop diuretics can cause significant potassium and magnesium losses analogous to those seen in Bartter syndrome, while thiazide diuretics can lead to the kind of electrolyte disturbances observed in Gitelman syndrome, including hypokalemia and hypomagnesemia. While other answer choices mention factors that could potentially be involved in renal pathologies, the quintessential feature of both Bartter