Massive change in my DM :(

The hallucinations and erratic behaviour make it sound like Lewy Bodies Dementia. My family member would also see spiders webs, Lilliputian children, rain on the window and was convinced people were trying to steal her purse, handbag or sewing machine.

The same thing use to happen to my auntie when she had a uti, often wouldn't show up on the dipstick test. you say she was dehydrated they often go hand in hand, could you ask for some antibiotics specifically for water infections just to totally rule it out

When she’s been talking rubbish we’ve not engaged with her as she’s clearly ‘right’ in what she’s saying and is convinced she’s right. You're right not to try to reason with her, it is just distressing for her, but see if you can engage a bit, eg saying you'll talk to your dm about the red letters and make sure she doesn't hide any in the future (ie don't admit she has been hiding them, don't deny it either, but give her hope that this fantasy she's afraid of will be dealt with).

I should add to my post that my dm had episodes, so could have these hallucinations for a period and then be ok, well as ok as you can be with dementia. I wish you and your family all the best and hopefully investigations will give you a clearer picture.

My mum's dementia started like this. Erratic behaviour and she kept saying she saw things that weren't there or there were objects there but she saw them as something entirely different. She was eventually diagnosed with mixed dementia - vascular and Alzheimer's

Honestly I would ask to get her calcium levels checked for the possibility of cancer
Your mum sounds just like my mum was behaving

My mum was so bad she thought my sister was her dead cat 😂

My mum was like this, literally like Freddy Kruger on a shit load of speed 😂
She had cancer and very high levels of calcium which was causing the confusion and aggression
I would push for a MRI / Scan and check for calcium levels
They treated the cancer and we got another 3 years with her

Sadly those 3 years she had dementia and Alzheimer’s but could still do a good impression of Freddy Krueger mother 😂

Check that b12 is one of the blood tests they are doing, as this being low can cause hallucinations too.

Delirium can have a variety of causes including infections of any kind, metabolic disturbances eg dehydration and low sodium and new medication especially opiate painkillers. You have to hope the hospital has done their job in ruling these out/ treating them but the mental disturbance does persist after the cause is treated so doesn't necessarily mean anything was missed. If she isn't getting better after a week or two or getting worse then back to GP to take some more blood tests.

You cannot diagnose or rule out dementia on a scan alone in fact. It's on the history of symptoms and cognitive tests.

The suddenness and severity though is unlikely to be dementia and more likely delirium due to the kidney infection. The delirium can persist for weeks after the physical cause resolves but should resolve in the end.

In the meantime she might need some different medication to help her behaviour and distress in the short term which old age psych are best to advise on.

OP, keep pressing for proper investigation. My DM went like this overnight. The hospital said she must have dementia and that was that. We pressed for further investigation and it turned out she had an infection in her heart and once she was given antibiotics in hospital, she was much better. She had two more episodes of confusion before she died, she said the most awful things to everyone and stayed up all night talking to herself. She had previously had sepsis and kidney problems before developing the infection in her heart. Good luck OP. I really feel for you and your mum and family.

'Doing alright now' means, we had the person in hospital for a couple of nights or more, it wasn't down to me and Diolyte sachets!
Also, the drip replenishment needs to be slow, otherwise it can cause permanent mental harm, I was told.

This has prob been checked but this kind of behaviour is not just caused by a UTI but also low sodium levels. Talking gibberish, getting up and wandering around, falling over etc.
It is cured by a two or three-day stint in hospital on a drip, very slowly replenishing the sodium levels.
Reluctance to do this due to the Covid thing and you just might look at using one or two sachets of Diolyte daily to do a similar thing but that is more to ward it off or reduce the impact and I'm not a medical person, but it won't do harm. It certainly won't sort the problem by itself but it just might alleviate the worst effects.
I was taking urine samples to the GP thinking well if it's not a UTI we are really stuffed, it's game over. This was some years ago and 'patient' is doing alright now.

My mother had vascular dementia and suffered from terrible auditory hallucinations.

My father in law had Lewey Body Dementia and had similar episodes - lots of hallucinations- things in food, people in the house, report water pouring into his room etc. He seemed to be lucid a lot, charmed doctors and answering questions perfectly. We reached a crisis point and had to have him admitted to hospital. It’s a horrible time. I hope things work out for your mum.

So sorry you're going through this. Have they said anything about her kidneys? My lovely late Grandfather had renal failure; was diagnosed at stage 2 and as soon as he reached stage 5 he became so very confused and disorientated