Yes, a urine infection can cause delirium in an older person. But it is often blamed when it is not the cause, and stopping there can mean the real cause is missed.
Infection anywhere in the body can disturb an older brain, and the urinary tract is a common site. If someone has a real urine infection and becomes confused, treating the infection is part of treating the confusion.
Why a positive test proves little
Bacteria in the urine are very common in older people who have no infection at all. They are commoner in women, and commoner still in anyone with a catheter. There is a name for it: asymptomatic bacteriuria. The bacteria are there. They are doing no harm, and they do not need antibiotics.
By the age of 80, about half of older people in care homes have bacteria in the urine without having an infection.
This is why national guidance says urine dipsticks should not be used to diagnose a urine infection in anyone over 65. The strip often turns positive whether or not there is an infection. Not every ward has caught up with this.
What else could be causing it
Someone comes in confused. A dipstick is done and shows something. Urine infection goes in the notes, antibiotics are started, and the search stops.
Meanwhile the cause might be a new medicine, constipation, dehydration, pain, low oxygen, a chest infection, a small stroke or alcohol withdrawal. Often it is several of these at once.
National guidance tells staff to work through that same list whenever an older person is confused: pain, infection elsewhere, poor nutrition, constipation, poor hydration, medicines, and a change of surroundings. So if you ask what else has been considered, you are asking for exactly what the guidance recommends.
What to ask
None of this means refusing antibiotics or arguing with the team. It means keeping the question open. If you have been told it is a urine infection, you can ask what else has been looked for.
And if nothing has changed a few days later, you can say: the antibiotics have been running for three days and she is no clearer, so what else could be causing this?
Two things are worth bringing to that conversation, because ward staff have no way of knowing them. The first is which medicines were started or changed in the last week or two, including anything bought over the counter. The second is when the person last opened their bowels. Constipation and a full bladder are both common causes of delirium, and both are easily missed and easily treated.
When to get help
New confusion that has come on over hours or days needs medical advice the same day. Phone the GP practice, or 111 when it is closed. Phone 999 if the person cannot be woken, has collapsed, or has new weakness or new trouble speaking. When you speak to someone, say what has changed. Then ask: could it be delirium?