Catheters and Size

Urinary catheters are thin, flexible tubes that are inserted into the urethra to empty out the bladder. They are used by people who are unable to drain out the urinary bladder on their own either because of a surgery, urinary incontinence and enlarged prostrate or other medical reasons. Urinary Catheters may be used by both men and women and can either be permanent or temporary, one which is removed after every catheterization.

Sizes of Urinary Catheters

The size of a catheter is calculated in FR – that is French scale or French gauge system. It was devised by a 19th-century Frenchman named Joseph-Frédéric-Benoît Charrière, a maker of surgical instruments.

FR indicates the diameter of the tube and the higher the number, the larger the diameter. 1 FR is equal to 3 mm and so the diameter of a round catheter in mm can be determined by dividing the French size by 3. A catheter with a diameter of 4.7 mm will have an FR size of 14.

The common Foley catheter sizes are in the range of 10 FR to 28 FR.A 16 French Foley catheter indicates a Foley catheter size and means an indwelling catheter with an FR size of 16.

Catheter sizes available are from pediatric to adult. Doctors would help determine the right size for you.

Other than the Urinary Catheters size, the length of the tube is also important. This also should be determined by your doctor. He will base his decision about catheter length on the patient’s body type and the procedure meant to be carried out.

Catheter lengths vary. Catheter length pediatric is around 10 inches, catheterlength female is 6-8 inches and catheterlength male or unisex is 16 inches. Foley catheter length is standard 46 cm. Men need longer catheter tubing and this is usually between 40 and 45 cm. For females the standard length is 25 cm.

For example, if the patient is heavy in weight and size then the doctor is likely to go for a longer catheter tube. Again, a female would require a shorter catheter size tube in comparison with the male. Also, a shorter length is always advised for better efficiency. The longer the tube, the greater is the drawing-out period.

It is important to get the catheter sizing right. The reason is three-fold. If the FR is smaller than what is needed, then the emptying out of the bladder will take time. If the FR is too big for the urethra, then there will be difficulty and pain when inserting the catheter. A catheter size larger than required is more likely to cause trauma and mucosal irritation. If the catheter is smaller than the urethra then there will be leakage of urine.

However, one must keep in mind that if there is the chance of blood clots passing through the catheter or large volumes of fluid flow, following an infection or postoperative bleeding, then the catheter should be slightly larger. This would minimize the chance of obstruction.

The general rule is to select the smallest possible size that is suitable for a particular procedure but one which will allow effective drainage. Usually, a doctor would opt for FR 14, which is about 4.7 mm, if it is meant for an adult male, and FR 12-16, around 4-5.3 mm, if it is for an adult female.