Foley catheter

Diagram of a foley catheter

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Foley catheters are flexible (usually latex) tubes that are passed through the urethra during urinary catheterization and into the bladder to drain urine. They are retained by means of a balloon at the tip which is inflated with sterile water. The balloons typically come in two different sizes: 5 cc and 30 cc. They are commonly made in silicone rubber or natural rubber.

The relative size of a Foley catheter is described using French units (F).^[1] 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.

Side view diagram of male urinary tract with Foley catheter in place to drain urine. A balloon near the tip holds the catheter in place.

Foley catheter (F/Ch. 24) positioned in a male; 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. Council tip catheters have a small hole at the tip which allows them to be passed over a wire. 3-way catheters are used primarily after bladder, prostate cancer or prostate surgery. They have a third arm or bell that allows an irrigant to pass to the tip of the catheter through a small separate channel into the bladder. This serves to wash away blood and small clots through the primary arm that drains into a collection device. This prevents larger clots, which might plug the catheter, from forming. The second, or inflation, arm has a small plastic valve that allows for the introduction or removal of sterile water through a very small channel to inflate or deflate the retaining balloon.

Foley catheters can also be used to "ripen" the cervix, to allow the induction of labour. The catheter is inserted behind the cervical wall and inflated. The remaining length of the catheter is gently pulled and taped to the inside of the woman's leg. The inflated balloon applies pressure to the cervix, like the baby's head would prior to labour, causing it to dilate. Over time the catheter is adjusted and re-taped to maintain pressure on the cervix. When the cervix has dilated sufficiently, the catheter simply drops out.^[2]

They were designed by Frederic Foley, a surgeon working in Boston, Massachusetts, in the 1930s, when he was a medical student.^[3]

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.

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 antibiotic 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 with time with a biofilm that can keep them from properly draining the bladder. This increases the degree of static 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. Thus keeping Foley Catheters from clogging may help reduce UTIs as well.

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
• Sometimes before Furosemide administration

Alternative treatments

• For obstructed prostates due to BPH: The Spanner Prostatic stent

Notes

1. ^ Dorland's Illustrated Medical Dictionary
2. ^ WHO article on induction of labour
3. ^ 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. 

External links

• Foley Catheter Video
• Male urethral catheterization video