What is a urethral or "Foley" catheter?

A urethral or "Foley" catheter is used to provide continuous bladder drainage. The catheter is named after a Boston urologist, Dr. Frederic Foley, who was instrumental in creating the catheter in the 1930's.


Here are some reasons why a patient would have one:

• monitor urine output
• alleviate urinary retention or severely dysfunctional voiding
• realign the urethra and bladder after urologic surgery or trauma
• help stop lower urinary tract bleeding

They are sized on the  French scale.  The diameter of the catheter x 3 = French size.  Here is a good link on Wikipedia on this scale. The most common sizes for routine use are 16F and 18F.

Urethral catheter
 Source: Wikimedia Commons/Olek Remesz
Creative Commons Attribution-Share Alike 3.0 Unported License

The catheter is placed inside the urethra and allows the bladder to continuously drain via a closed drainage system.  One the left side of the diagram there is a balloon port and a urine drainage port. The balloon port is where a syringe is placed to fill the balloon with fluid at the right side of the diagram.  The balloon is needed to keep the catheter in the bladder.  Without the balloon, the catheter would simply slip out.


The urine drainage port is connected to a drainage bag.  There are two types of drainage bags:


Leg Bag- a small bag with elastic straps that can be placed on the leg.  This allows the patient to discretely wear the bag under pants and move about.


Overnight Bag - this bag is larger and is usually used at night because of its capacity.  This is placed at the side of the bed, attached to an IV pole, or carried by a patient.


There are many other catheters out there that urologists primarily use.  One noteworthy example is a 3-way catheter that is used to treat urinary tract bleeding.  This catheter has an additional inflow port that is used to irrigate the bladder.  This fluid then goes out the drainage port with the urinary output.  


Reference: http://en.wikipedia.org/wiki/Foley_catheter