Catheter size refers to the circumference of the catheter, not the luminal diameter and is recorded in French sizes (1 French (F) = 1 Charrière = 0.33 mm).
Choose the smallest catheter that will allow adequate urinary drainage. Size 12–14F is usually adequate for males and females. Use size 16–20F if the patient has urine with debris, mucous, blood clots or haematuria, which may occlude smaller lumens. A 22F triple lumen is the standard size for bladder irrigation and ‘washout’. Smaller sizes (6–10F) are available for children.
