AST Surgical Technologist Exam Practice 2026 – Complete Study Resource

The commonly used size of Foley catheter for adults is generally considered to be 16 French (Fr). This size strikes a balance between sufficient drainage capacity and patient comfort. A 16 Fr catheter is effective for most adult patients needing urinary drainage, as it allows for adequate flow while minimizing the risk of trauma to the urethra and bladder.

Larger sizes, such as 18 Fr or 20 Fr, might be required in specific clinical situations, such as when retrieving larger blood clots or in patients with certain urological conditions, but they are not the standard for routine use. A 14 Fr catheter is typically employed in pediatric populations or in adults with stricter indications for smaller sizes. Therefore, 16 Fr is recognized as a standard size in adult catheterization practices.