What is a Foley Catheter and how does it work?

The Foley catheter is a type of flexible catheter used to drain urine from the bladder to the outside. For this reason it is also commonly known as a urinary catheter or bladder catheter.  The material of the tube is usually latex because it is more comfortable for the patient. However, if the person is allergic to latex, another type of plastic can be used to maintain the sterility of the probe to prevent infection.  As a curiosity, it should be noted that these probes are named after Dr. Foley, an American surgeon.

What is the design of the Foley probe?

The Foley catheter is inserted through the urethra and has to reach the bladder, so it is a tube that must adapt to different sizes. For this reason there are varieties for children, women and men. There are also different thickness gauges so that they adapt better to the particularities of the anatomy of each patient.

There is a scale that serves to describe the size of the catheters. It is the French scale of Charriére where one unit equals 0.33 mm.The number of Charrière units is equivalent to the size of the circumference of the catheter in millimeters. That is, with the number of Cherriere units (represented by the symbol F) we can know the diameter of the probe and, therefore, the urethra.

Despite the range of probes, they all have one thing in common which is the fact of having incorporated into the tube an inflatable ball that comes standard deflated. The balloon is a crucial element for the Foley probe to function correctly since it is the only element of the design that allows the probe to not escape.

What is the placement technique of the Foley catheter?

Before proceeding with the installation, check that the probe is not defective. Nowadays manufacturers' houses carry out very strict quality controls, but even so it is not uncommon that from time to time there are problems with the probe because it is simply defective.

To check that the probe works, you have to introduce sterile water into the nozzle housed in the balloon. If we see that the balloon swells and there are no water leaks, then we can proceed to place the probe in the patient.

The patient has to have perfectly clean genitals. With the help of a little lubricant, the probe is carefully inserted through the urethra. To facilitate the entrance of the tube into the bladder, abdominal pressure can be made by breathing maneuvers or by simulating the act of urinating.

Once the tube is already lodged in the bladder, the balloon must be filled to prevent the tube from escaping. With the help of a syringe the balloon of air or sterile water is filled into the nozzle housed with a small valve.

Finally, the valve of the catheter itself is connected to a bag so that the urine is stored. To facilitate volume measurement there are usually graduation marks on the bag, usually in milliliters.

What is the Foley catheter used for?

The most frequent indications of the Foley probe are:

  • Urinary incontinence: is typical in the elderly and in patients who have suffered neurological damage where the nerves responsible for urination are damaged.
  • Any situation that prevents the complete emptying of the bladder: is the case of prostate cancer.
  • Patients who have undergone surgery and have to control the volume of urine eliminated.

What are the drawbacks of the Foley catheter?

The main problem when using the Foley catheter is the risk of urine infection. The catheter does not stop being a foreign body lodged in an area where bacteria can be dragged from the outside of the genitals into the bladder. For this reason we must pay special attention to intimate hygiene.

In addition, it is important to prevent the drainage bag from twisting so that the flow of urine is not interrupted and accumulates retrograde. A simple way is to fix the catheter with tape to the thigh or if the patient is bedridden leave the bag under the bed so that the urine flows in favor of gravity.