A Foley is a flexible tube inserted through the urethra into the bladder to drain urine. Formally called a Foley catheter, it’s one of the most common medical devices used in hospitals, named after the surgeon Frederic Foley who introduced the balloon-tipped design in 1937. What makes it different from other catheters is a small inflatable balloon near the tip that holds it in place inside the bladder, allowing it to stay in for hours, days, or even weeks without slipping out.
How a Foley Catheter Works
The catheter has two internal channels running through a single tube. One channel drains urine from the bladder into a collection bag. The second channel connects to the balloon at the tip, which a nurse inflates with sterile water after the catheter is positioned inside the bladder. Once inflated, the balloon sits against the bladder’s internal opening and prevents the tube from falling out. The other end of the catheter connects to a drainage bag that collects urine continuously.
Most Foley catheters are made from silicone or latex-coated materials. Silicone tends to be used for people who need the catheter longer or who have latex allergies. The basic design has remained largely unchanged since the 1930s.
Catheter Sizes
Foley catheters are measured using the French scale, where each French unit equals one-third of a millimeter in diameter. A 14 French catheter, for example, has a diameter of about 4.7 millimeters. Most adult women use sizes ranging from 12 to 16 French. Most adult men use 14 to 18 French. Children and adolescents typically use 8 to 12 French, while the smallest sizes (5 or 6 French) are reserved for babies and infants. Your healthcare team selects the size based on your anatomy and the reason for catheterization.
Why Doctors Use a Foley
The most common reason is urinary retention, meaning the bladder can’t empty on its own. This can happen for many reasons. An enlarged prostate is the most common cause in men. Infections like prostatitis or cystitis, nerve damage from spinal cord injuries or stroke, and certain medications with anticholinergic properties can all prevent normal urination. Kidney stones, tumors, or scar tissue in the urinary tract can physically block urine flow.
Surgery is another major reason. Nearly all abdominal and pelvic surgeries, including gynecological and urological procedures, involve a Foley catheter. It keeps the bladder empty during the operation and lets the surgical team monitor exactly how much urine the kidneys are producing, which is an important indicator of how the body is handling the procedure. After surgery, anesthesia can temporarily make it difficult to urinate, so the catheter stays in until normal bladder function returns.
Foleys are also used for people who are critically ill and need precise fluid monitoring, for managing severe urinary incontinence, for delivering certain chemotherapy drugs directly into the bladder, and for flushing the bladder with irrigation fluid.
What Insertion Feels Like
Insertion is a sterile procedure. The nurse or clinician cleans the area around the urethra with antiseptic solution, sets up a sterile field with drapes and gloves, and applies lubricating jelly to the catheter tip before gently advancing it through the urethra into the bladder. The entire process typically takes only a few minutes.
Sterility matters enormously. If the catheter accidentally touches anything non-sterile (skin, clothing, the bed), the CDC guidelines require that it be discarded and a fresh one used. This strict protocol exists because the catheter creates a direct path for bacteria to enter the bladder. You’ll likely feel pressure and mild discomfort during insertion, but it should not be sharply painful.
Infection Risk
The biggest risk of having a Foley catheter is developing a urinary tract infection. The daily risk of bacteria colonizing the bladder while a catheter is in place ranges from 3% to 10%. After 30 days of continuous use, that risk approaches 100%. This is why healthcare teams aim to remove the catheter as soon as it’s no longer medically necessary. Catheter-associated urinary tract infections are one of the most common hospital-acquired infections, and minimizing the time a catheter stays in is the single most effective way to prevent them.
Living With a Foley Catheter
If you go home with a Foley, the drainage bag needs to stay below your bladder at all times so urine flows downward by gravity and doesn’t back up into the catheter. When you’re walking, hold the tubing with the bag below your waist. At night, hang the bag on the side of the bed, never on the floor. You can sleep in any position as long as the bag remains lower than your hips.
Most people use two types of bags: a smaller leg bag during the day that straps to your thigh or calf under clothing, and a larger bedside bag for overnight. Clean your bags every day and wash your hands thoroughly before and after handling any part of the system. Keeping the area where the catheter enters your body clean is essential for reducing infection risk.
How Long a Foley Stays In
There’s no single universal schedule for how long a catheter can remain before it needs to be swapped. Guidelines vary, and the Infectious Diseases Society of America has stated there isn’t enough data to recommend one specific replacement interval. In practice, most guidelines recommend changing the catheter when there are signs of infection or blockage rather than on a fixed calendar. Some institutions allow catheters to remain for up to 12 weeks, while others flag any blockage occurring before six weeks as a reason to investigate underlying problems. Your care team will base the timeline on the catheter material, your history of blockages, and the manufacturer’s recommendations.
Removal and Recovery
Removing a Foley is much simpler than putting one in. The balloon is deflated by withdrawing the sterile water through the same channel used to inflate it, and the catheter slides out. Most people feel brief discomfort but describe it as far less bothersome than insertion.
After removal, the healthcare team typically wants to confirm your bladder can empty on its own. This is called a voiding trial. In many post-surgical settings, the catheter is removed about six hours after the procedure, and you’re asked to urinate naturally. An ultrasound scan of the bladder after you void measures how much urine is left behind. If less than about 150 milliliters remains, your bladder is working well. If a significant amount is retained, temporary re-catheterization may be needed.
It’s common to feel some burning or urgency for the first day or two after a catheter comes out. Drinking plenty of water helps flush the urinary tract and ease these symptoms. Most people return to completely normal urination within a few days.