Which phase is used to evaluate calculus before any contrast is given in CT urography?

Which phase is used to evaluate calculus before any contrast is given in CT urography?

• A. Non-contrast phase.
• B. Nephrographic phase.
• C. Excretory phase.
• D. Delayed phase.

Answer: (A)

Calculus detection is best accomplished on a non-contrast CT because calcium-containing stones are highly radiodense and show up clearly without any contrast in the urinary tract. Introducing IV contrast or performing phases after contrast can blur or obscure small stones by filling the lumen with contrast and by enhancing the surrounding tissues, making stones harder to distinguish. Therefore, the pre-contrast phase is acquired specifically to detect and size the stones before any contrast is given. After this non-contrast assessment, contrast-enhanced phases are used to evaluate the rest of the urinary tract and surrounding structures, but they’re not optimal for initial calculus detection.

Calculus detection is best accomplished on a non-contrast CT because calcium-containing stones are highly radiodense and show up clearly without any contrast in the urinary tract. Introducing IV contrast or performing phases after contrast can blur or obscure small stones by filling the lumen with contrast and by enhancing the surrounding tissues, making stones harder to distinguish. Therefore, the pre-contrast phase is acquired specifically to detect and size the stones before any contrast is given. After this non-contrast assessment, contrast-enhanced phases are used to evaluate the rest of the urinary tract and surrounding structures, but they’re not optimal for initial calculus detection.