Contrast Media and Reactions — MCQs

Q: What percentage of gallstones are radioopaque?

20%. ***20%*** - Approximately **10-20%** of gallstones contain enough **calcium** to be visible on plain abdominal radiographs, with **20%** being the most commonly cited figure in standard radiology references. - These radioopaque stones typically contain **calcium carbonate** or **calcium bilirubinate**. - The vast majority of gallstones are composed primarily of **cholesterol** (80-90%), which are **radiolucent** and not visible on plain X-rays. - **Ultrasound** remains the imaging modality of choice for gallstone detection, with sensitivity >95%. *10%* - While 10% represents the lower end of the accepted range (10-20%), most standard radiology references cite figures closer to **15-20%**. - Using 10% would be an overly conservative estimate that underrepresents the proportion of calcified gallstones. *30%* - 30% significantly overestimates the percentage of gallstones that are **radioopaque**. - This would suggest greater utility of plain radiography than is clinically observed. - Such a high percentage contradicts the well-established predominance of **cholesterol stones**, which constitute 80-90% of all gallstones. *40%* - 40% is far too high and contradicts established medical literature. - This would imply that nearly half of gallstones contain substantial **calcium**, which is inconsistent with their known composition. - Plain abdominal radiographs have low sensitivity (10-20%) for gallstone detection, making this percentage clinically unrealistic.

Q: Substance utilized for a barium meal follow-through study is:

Barium sulphate. ***Barium sulphate*** - **Barium sulphate** is the compound used due to its high radiopacacity, allowing for clear visualization of the gastrointestinal tract on X-ray. - It is chemically inert and poorly absorbed in the gastrointestinal tract, minimizing systemic toxicity. *Barium carbonate* - Barium carbonate is **toxic** if ingested, primarily used in industrial applications and ceramics. - It is not suitable for medical imaging due to its solubility and potential for harmful systemic absorption. *Barium oxide* - Barium oxide is a **highly reactive** and corrosive substance, used in industrial applications. - Ingestion would cause severe irritation and chemical burns to the gastrointestinal tract. *Barium hydroxide* - Barium hydroxide is a strong base and is **corrosive**, making it unsuitable for internal consumption. - It can cause severe gastrointestinal irritation and systemic toxicity if ingested.

Practice by Chapter

Chemistry of Contrast Media

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Pharmacokinetics of Contrast Agents

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Classification of Contrast Reactions

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Risk Factors for Contrast Reactions

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Prevention of Contrast Reactions

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Treatment of Acute Contrast Reactions

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Contrast-Induced Nephropathy

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Nephrogenic Systemic Fibrosis

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Extravasation of Contrast Media

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Guidelines for Contrast Administration

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Alternative Contrast Agents

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Documentation and Medicolegal Aspects

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