Foley catheter

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Diagram of a foley catheter

Diagram of a foley catheter

Ultrasound image of a foley catheter

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.

Side view diagram of a three-way Foley catheter, in place for bladder irrigation and drainage. The balloon near the tip holds the catheter in place.

Foley catheter (F/Ch. 24) balloon blocked and outlet plug put on.

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. "Councill 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.

When Foley catheters are used

Foley catheters are used during the following situations:

• On patients who are anesthesized or sedated for surgery or other medical care
• On comatose patients
• On some incontinent patients
• On patients whose prostate is enlarged to the point that urine flow from the bladder is cut off. The catheter is kept in until the problem is resolved.
• On patients with acute urinary retention.
• On patients who are unable due to paralysis or physical injury to use either standard toilet facilities or urinals.
• Following urethral surgeries
• Following ureterectomy
• To ripen the cervix during induction of labor
• On patients with kidney disease whose urine output must be constantly and accurately measured
• On c-section patients

They are also used in cases of severe epistaxis, in order to block blood from freely flowing down the nasal passage into the mouth.

Notes

1. ^ Foley, FE (1937). "A hemostatic bag catheter: one piece latex rubber structure for control of bleeding and constant drainage following prostatic resection". J Urol 38: 134–9. 
2. ^ Dorland's Illustrated Medical Dictionary
3. ^ WHO article on induction of labour

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