Catheters and Urinary Infections: What Actually Helps

A urinary catheter is the single largest risk factor for urinary infection in healthcare, and the risk is not subtle: it accumulates for every day the catheter stays in. After a month, bacteria are present in the urine of essentially everyone with a catheter.

That last sentence sounds alarming and is the key to the whole subject. Bacteria in the urine of someone with a catheter is expected. It is not, on its own, an infection, and treating it as one causes more harm than it prevents.

Why a catheter changes everything

A catheter provides a direct route from outside the body to the bladder, and a surface for bacteria to form a biofilm on — the same phenomenon described in our article on infection after a joint replacement. It also stops the bladder emptying and refilling in the way that normally flushes organisms out.

The consequence is that colonization is universal over time and cannot be prevented by anything you do at home. What can be influenced is whether it turns into illness, and how long the catheter stays in at all.

Bacteria in the bag versus an infection

What is expected, and what is not

	Colonization	Infection
Bacteria present	Yes	Yes
Cloudy or smelly urine	Common, and not a reason to treat	May or may not be present
Fever	No	Often
New pain or discomfort	No	Suprapubic or flank pain
New confusion	Not from this	Possible, especially in older adults
What should happen	Nothing; no antibiotics	Assessment, and usually a catheter change

The reason this matters is not pedantry. Treating colonization exposes someone to C. difficile, drug reactions and resistance, and it selects for organisms that are harder to treat when a real infection eventually happens.

Why this matters more in older adults

Catheters are commonest in exactly the group where the consequences of getting this wrong are greatest. An older adult with a catheter may develop confusion during a genuine infection, and may equally be confused for reasons that have nothing to do with the urine.

Our article on infections in older adults covers the central point: confusion alone, with bacteria in the urine, is not sufficient evidence of urinary infection, and treating on that basis is one of the commonest sources of unnecessary antibiotics in older people. The question to ask is whether anything else has changed — fever, new pain, a change in the urine output rather than its appearance.

What actually reduces infection

1. Not having one. The most effective intervention by a wide margin is removing the catheter as soon as it is not needed, and asking regularly whether it still is.
2. Hand hygiene before and after handling the catheter or bag, every time, by everyone.
3. Keeping the bag below the bladder and never resting it on the floor, so urine cannot flow back.
4. Keeping the system closed — not disconnecting it unless there is a reason.
5. Securing the tube so it does not pull, which causes trauma and lets organisms in.
6. Routine daily washing of the area with soap and water, which is sufficient.

What does not help, despite being widely recommended

• Cranberry products, which have not been shown to prevent catheter-associated infection
• Antiseptics in the bag or antibiotic bladder washouts, which do not reduce infection and do breed resistance
• Routine catheter changes on a schedule, in the absence of a reason, for most people
• Antibiotics at catheter change, other than in specific situations
• Antibiotics because the urine looks or smells unpleasant
• Routine urine testing when the person is well, which finds bacteria that then get treated unnecessarily

One more distinction is worth making. A catheter that has been in for a long time will almost always grow something if the urine is cultured, so a culture is worth sending when there is a clinical reason and not otherwise. Where infection is suspected, the recommended practice is to change the catheter and take the sample from the new one, because a sample drawn through an old biofilm-coated tube tells you about the tube rather than about the bladder. Our article on culture and sensitivity results explains why the sample governs what the report can mean.

Types, and the questions worth asking

Not all catheters are the same, and the alternatives are worth raising rather than assuming the current arrangement is fixed.

• Indwelling urethral — the usual type, and the one with the highest infection risk over time
• Suprapubic — through the abdominal wall, often more comfortable long term and easier to manage
• Intermittent self-catheterization — draining several times a day rather than leaving a tube in, which carries substantially less infection risk for people who can manage it
• External or sheath devices, for men, which avoid entering the bladder at all

Intermittent catheterization is the one most worth asking about. It is more effort day to day and it removes the permanent foreign body, which is where most of the infection risk comes from.

When to call

• Fever, shivering or feeling generally unwell
• New pain in the lower abdomen or the side
• New confusion or a change in behavior in an older adult
• The catheter not draining, or leaking around it
• Blood in the urine that is new or increasing
• Any of the warning signs of sepsis
• The catheter coming out, which needs prompt advice rather than panic

A catheter blocking is a common and treatable problem rather than an emergency in itself, but it needs attention the same day, because a blocked catheter causes pain and can precipitate infection.

If urinary infections keep recurring around a catheter, or a resistant organism has been found, a specialist review can help sort out what is worth treating and what is not. Our articles on recurrent urinary infections and kidney infection cover the situation without a catheter, and you can reach us through the contact page.

Frequently asked questions