A Foley catheter is a flexible tube that is often passed through the urethra and into the bladder. The tube has two separated channels, or lumens, running down its length. One lumen is open at both ends, and allows urine to drain out into a collection bag. The other lumen has a valve on the outside end and connects to a balloon at the tip; the balloon is inflated with sterile water when it lies inside the bladder, in order to stop it from slipping out. Foley catheters are commonly made from silicone rubber or natural rubber.
The name comes from the designer, Frederic Foley, a surgeon working in Boston, Massachusetts in the 1930s.[1] His original design was adopted by C. R. Bard, Inc. of Murray Hill, New Jersey, who manufactured the first prototypes and named them in honor of the surgeon.
The relative size of a Foley catheter is described using French units (F).[2] The most common sizes are 10 F to 28 F. 1 F is equivalent to 0.33 mm = .013" = 1/77" of diameter. Thus the size in French units is roughly equal to the circumference of the catheter in millimetres.
Foley catheters come in several sub-types: "Coudé" (French for elbowed) catheters have a 45° bend at the tip to allow easier passage through an enlarged prostate. "Council tip" catheters have a small hole at the tip which allows them to be passed over a wire. "Three way" or "triple lumen" catheters have a third channel, which is used to infuse sterile saline or another irrigating solution. These are used primarily after surgery on the bladder or prostate, to wash away blood and blood clots.
A Foley catheter can also be used to "ripen" the cervix, to allow the induction of labour. The balloon is inserted behind the cervical wall and inflated. The remaining length of the catheter is pulled slightly taut, and taped to the inside of the woman's leg. The inflated balloon applies pressure to the cervix, as the baby's head would prior to labour, causing it to dilate. As the cervix dilates over time, the catheter is readjusted to again be slightly taut, and re-taped to maintain pressure on the cervix. When the cervix has dilated sufficiently, the catheter simply drops out.[3]
A major problem with Foley catheters is that they have a tendency to contribute to urinary tract infections (UTI). This occurs because bacteria can travel up the catheters to the bladder where the urine can become infected. To combat this, the industry is moving to antiseptic coated catheters. This has been helpful, but it has not completely solved this major problem. An additional problem is that Foley catheters tend to become coated over time with a biofilm that can obstruct the drainage. This increases the amount of stagnant urine left in the bladder, which further contributes to the problem of urinary tract infections. When a Foley catheter becomes clogged, it must be flushed or replaced.
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Foley catheters are used during the following situations:
They are also used in cases of severe epistaxis, in order to block blood from freely flowing down the nasal passage into the mouth.
There are several risks when using a Foley catheter (or catheters generally), including:
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