Fever of unknown origin

Old collie

An old collie called Gemma came to me during the heatwave last month.

She was rising thirteen, and had been experiencing a good retirement, until a few days
earlier when her owners noticed she seemed lethargic. As the weather was extraordinary
they were not too concerned at first, but when she refused her food, they knew it was time to
call us.

She had to be carried into the Clinic in her bed, but got herself up once she arrived in our
cool consulting room. I performed my usual physical examination, and the stand-out problem
was an extreme fever. Her temperature was two and a half degrees above normal. This is
extremely high.

It could have been heat stress, but I suspected that this was not the full answer.
I went over her again, this time looking for sources of infection. Was it a foreign body under
her skin, or an infected claw, womb, mammary gland or tooth? I could not find anything. And
so I got to label her problem with an acronym I have always wanted to use: PUO.

PUO stands for ‘pyrexia of unknown origin’.

Pyrexia is another word for high temperature, and I recall first noticing the term PUO on a
patient’s record at vet school, and being impressed firstly that it seemed slightly naughty,
and secondly that even our vet school professors might sometimes need to say, “I don’t
know what is causing this problem.”

There are always more diagnostic tests you can do to pursue a label to put onto a disease,
but Gemma’s owner and I elected to use the available budget for treatment.

Gemma spent a day in our air conditioned hospital, with a dedicated fan as well, just on her.
She received intravenous fluid therapy and antibiotics, plus medication to bring her fever
down.

At first I thought she would not respond, but after thirty-six hours we could see a definite
improvement in her energy levels, and she was eating a little. We stayed hopeful, continuing
her care, and were able to celebrate her being nearly back to normal a week later.

We never did identify the actual cause of her fever. It really was a true case of PUO.

10th September 2020

Category: Mewes memories