Nbme 3 question

[RedSoxSuck]

11. After eating, a 40-year-old woman has a vague feeling of discomfort in the right upper quadrant of the abdomen. Ultrasonography discloses several small calculi, believed to be cholesterol gallstones, in the gallbladder. She begins oral therapy with ursodeoxycholic acid. Which of the following is the best rationale for this treatment?

A. Addition of bilirubin to the bile
B. Decrease in the concentration of bile acids
C. Decrease in the ratio of cholesterol to bile acids
D. Increase in the ability of the gallbladder to concentrate bile
E. Increase in the concentration of lecithin in bile

I chose C but the key says B. Internet search has revealed for C and B as answer choices.

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[Phloston]

Answer is definitely C, not B, so you are correct.

To make your life easier (and FA should have included this), whenever you think of cholesterol stones, think of this equation/ratio:

Cholesterol / (bile salts + phosphatidylcholine)

As the ratio increases, there is increased likelihood of stone formation. So decreasing cholesterol concentration or increasing bile acid or phosphatidylcholine concentrations favors dissolution of cholesterol stones.

Ursodiol (ursodeoxycholic acid) is itself a secondary bile acid, so you know the ratio has to decrease, which favors dissolution.

Choice B doesn't make sense because even if that were the mechanism of ursodiol, decreasing bile acids would favor stone formation.

Quick facts for you (based on having done practice questions):

1) If a patient has gallstones and shoulder pain, the pain is due to inflammation of the liver, which contacts the diaphragm (referred pain), not the gallbladder.

2) The biggest risk for gallbladder adenocarcinoma is gallstones, not EtOH.

3) Meperidine is always the drug of choice for biliary colic because it doesn't cause contraction of the sphincter of Oddi, whereas morphine does.

 

[RedSoxSuck]

Answer is definitely C, not B, so you are correct.

To make your life easier (and FA should have included this), whenever you think of cholesterol stones, think of this equation/ratio:

Cholesterol / (bile salts + phosphatidylcholine)

As the ratio increases, there is increased likelihood of stone formation. So decreasing cholesterol concentration or increasing bile acid or phosphatidylcholine concentrations favors dissolution of cholesterol stones.

Ursodiol (ursodeoxycholic acid) is itself a secondary bile acid, so you know the ratio has to decrease, which favors dissolution.

Choice B doesn't make sense because even if that were the mechanism of ursodiol, decreasing bile acids would favor stone formation.

Quick facts for you (based on having done practice questions):

1) If a patient has gallstones and shoulder pain, the pain is due to inflammation of the liver, which contacts the diaphragm (referred pain), not the gallbladder.

2) The biggest risk for gallbladder adenocarcinoma is gallstones, not EtOH.

3) Meperidine is always the drug of choice for biliary colic because it doesn't cause contraction of the sphincter of Oddi, whereas morphine does.

Awesome. Thanks amigo!!