American Board of Internal Medicine (ABIM) Certification Practice Exam

Which metabolic condition is commonly associated with Roux-en-Y gastric bypass?

1. Hypomagnesemia

2. Hyperoxaluria

3. Hypocalcemia

4. Hypernatremia

The correct answer is: Hyperoxaluria

The metabolic condition most commonly associated with Roux-en-Y gastric bypass is hyperoxaluria. This condition occurs due to changes in intestinal absorption and the bacterial flora in the gut following the surgical procedure. Roux-en-Y gastric bypass alters the gastrointestinal tract significantly, leading to malabsorption of certain nutrients and an increased risk of oxalate absorption. In this procedure, food is rerouted past the stomach and a portion of the small intestine, which can lead to increased intestinal oxalate absorption. Moreover, due to altered calcium absorption associated with decreased intake and absorption of calcium, more oxalate is available to bind with calcium in the intestines. When calcium is bound to oxalate, the unbound oxalate can then be absorbed into the bloodstream, leading to hyperoxaluria. This increased oxalate level in urine can predispose patients to kidney stones, specifically calcium oxalate stones. While hypomagnesemia, hypocalcemia, and hypernatremia can also occur in patients who have undergone Roux-en-Y gastric bypass, these are less frequently encountered as primary metabolic conditions associated with the surgery compared to hyperoxaluria, making it the most appropriate answer in this context.