The Yorkshire Vet, Julian Norton is faced with a puzzle as he tries to help Mini the Guinea pig

They both munched furiously and listened intently.

At least I think they did. I’m pretty sure the squeaks and snuffles confirmed their agreement. I can say with confidence that they are excellent pets for small children and adults alike.

But when they go wrong, an ill guinea pig is an irksome challenge for any vet. They are difficult to examine and hard to investigate.

Blood samples are challenging – if not impossible – to collect and interpret; X-rays can be useful up to a point (mainly to detect bladder stones) but it’s hard to keep a ‘cavy’ stationary for the X-ray exposure. Sedation or general anaesthesia is not so straightforward either, so vets have to use a good dose of instinct and initiative.

Mini had been a maxi challenge from the start. Initially, the cute and bristly guinea pig had shown very vague signs.

She had a poor appetite and was reluctant to eat, but there were no other signs of illness. I examined her and checked her teeth – a common cause of GP malaise – but they were not too bad.

Precautionary radiographs did not reveal anything obvious, leaving us at something of a diagnostic dead end. Luckily, before long, a clue appeared. Mini developed a discharge. A course of antibiotics was called for, which cleared up the nasty pus and her appetite returned.

But as soon as the drugs finished, Mini relapsed, and it became clear that something more major needed to be done.

“I think we’ll need to operate,” I declared, outwardly confident but inwardly worried. My ambitious plan was to spay her, removing what was clearly a problematic uterus.

The last time I’d done this to a guinea pig, the patient had huge, cystic ovaries and it was very tense, particularly as the patient belonged to a primary school. There was not one, but 30 worried children on operation day.

Luckily, it was all fine and afterwards I was even invited to the school, where the pig was carried in for my inspection, sitting on a velvet cushion!

I hoped Mini’s surgery would be as smooth.

The day of Mini’s surgery arrived and I promised to call as soon as I’d finished, whether with good news or bad. Everyone was anxious – owner, vet and surgical nurse Lucy who had the unenviable job of maintaining a smooth anaesthetic.

Of course, she’s very good and I shouldn’t have been surprised that the GA and surgery went to plan. I peered at Mini’s ovaries and uterus which lay on the surgical drape. They looked surprisingly normal. I picked up the scalpel again and sliced into one floppy tube.

Its contents explained everything.

A piece of hay, less than one centimetre long, was lodged high up in the uterus, almost at the Fallopian tube. I have never seen anything like this before.

The spiky foreign body must have worked its way upwards and was the obvious cause of her illness.

It didn’t seem huge, but a quick calculation of relative scale confirmed that it would be approximately equivalent to a cocktail stick stuck in a Jack Russell!

I crossed my fingers that the removal of Mini’s mini fragment of hay would return her to maximum health!