Mavis is a 90-year-old woman who has a whole host of medical problems, with the main ones being left atrial dilatation (a large dilated heart chamber), chronic hepatitis, liver cirrhosis (liver inflammation leading to scarring), and a history of hepatocellular carcinoma (liver cancer) and surgical removal about ten years ago. She comes in with ankle swelling and pulmonary oedema (fluid in her lungs), for which she got diuretics (water removal medicines), a catheter inserted for me to see how much fluid she's getting in and peeing out, and non-invasive ventilation (a breathing device) for Type 2 Respiratory Failure (to help her breathe out the extra carbon dioxide she was having difficulty removing because of all the fluids still inside).

Mavis was getting a few complications from her treatment and illness, making her recovery even slower. When we'd gotten rid of most of the fluids, she developed blood in her catheter after a few days of it being in and I treated her for catheter-associated urinary tract infection with antibiotics and removed her catheter. As a result of her antibiotic use, she then developed diarrhoea, which tested positive for C. difficile (a usually very antibiotic-resistant large bowel organism that can flare during antibiotic use and cause bowel inflammation) requiring another bout of antibiotics for that infection. She had bouts of delirium (sleepiness and confusion usually due to a change in the body's equilibrium on top of a vulnerable brain, usually triggered by infection), which I put down to the back-to-back infections and periods of raised carbon dioxide levels in her blood.

After a week of diuresis (water offloading), we seemed to have hit a stagnant point. Her body weight was back to its baseline; I'd removed all her excess fluids. But she was slipping in and out of delirium still. Although delirium itself is fluctuant and can take up to months to resolve, she just doesn't seem to be getting better.

"Have we checked ammonia?" my senior says one day.

"Why?" I say. Raised ammonia is indicative of liver failure and decompensated liver disease and results in hepatic encephalopathy, another cause of acute confusion. She has multiple reasons for her fluctuating delirium as-is.

"She just looks a bit like a decompensated liver case."

We check her ammonia. Two days later it comes back as raised. We give Mavis a lot of laxatives (constipation causes overproduction of ammonia from the gut, normally rid by the liver, but accumulates in liver failure cases and causes confusion) and she brightens up within two days, back to her baseline of chatty and alert.

A week of rehab later, Mavis is ready for discharge. I couldn't help but feel it just never clicked with me to think of a third cause of her acute confusion.

(My senior is amazing.)