This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Which of the following catheter materials is most suited for long term is used 
Select and explain. 
A. Latex, B. Silicone, C. Rubber, D. Pol yurathane
B: Silicone
Answer: B: Silicone 
Explanation: Ans. is 'b' i.e., Silicone "Catheters made of silicone are, in general better tolerated over the long-term than those made of materials like latex and polyurathane." - Cambell, 8/e Also remember Catheter size is usually measured in French (fr) it refers to the outside circumference of the catheter, not the luminal diameter. (Thus a 20 fr catheter may have different luminal size for urinary drainage, depending on the type of material used for construction and the number of lumens within the catheter). 1 Fr = 0.33 nun in diameter thus 3 Fr = 1 mm in diameter (thus a 21 Fr catheter would be 7 mm in diameter)