The life of a veterinarian is not all glam and glitz and cute critters — you also need to be prepared to spend much of your career with your arm up rear ends.

Key points: Leo the lion went off his food and the vets were called in to perform an enema

Leo the lion went off his food and the vets were called in to perform an enema The vet had to put his hand down Leo's throat to administer anaesthetic

The vet had to put his hand down Leo's throat to administer anaesthetic A vet with smaller hands was called in to complete the job at the other end

Eighteen-year-old Leo is the oldest of the four African lions at Crocodylus Park in Darwin, and recently his keeper Bill Stevenson noticed something was not right.

"He was very keen to receive his food but not keen on eating it," Mr Stevenson said.

Vet Dr Ian Gurry was part of the team needed to administer Leo with an enema to relieve constipation. ( Supplied )

"Constipation can happen with big cats if they got a lot of bones in their food, but also a lot of hair and skin.

"It can compact in their stomach.

"With Leo it was stretching on a bit long."

All bunged up

Cue local vet Dr Ian Gurry from Parap Veterinary Hospital.

Dr Gurry knocked Leo out to confirm the diagnosis and perform an enema.

Three vet nurses were in the enclosure monitoring the levels of anaesthetic to make sure an angry lion did not get a rude awakening.

"It turns out the king of beasts is not immune to the most undignified of ailments," Dr Gurry told ABC Radio Darwin's Adam Steer.

"The only way to actually get an ET tube into them is by sticking your whole arm down their throat, with a couple of [the] colleagues that I trust most prising the jaws apart.

"Lions are quite sensitive to certain drugs so we need to be pretty precise with the dosages that we use and be confident that they are asleep enough before we do what we need to do.

"Once that's in order we have to move to the other end of the digestive tract."

That is when the real trouble started.

"I've got pretty small hands, but it turns out not small enough," Dr Gurry said.

"One of my colleagues Vanessa has smaller hands and a lot of commitment.

"With large animals you use an elbow-length glove. We only stock the small gloves. She took one for the team."

Was this not in the job description?

Fortunately, Dr Vanessa Hick grew up on a cattle farm and spent plenty of her youth with her arms where the sun don't shine.

Dr Ian Gurry and Dr Vanessa Hick administering an enema on an anesthetised Leo. ( Supplied )

She was hoping for a cruisy Monday morning at work.

"It was a fairly exciting moment for me I guess. There's a few parts of my career and study which brought me toward this day. It was a career highlight I'd say," Dr Hick said.

"I treated it like any other animal. I did thank myself I had some experience with cattle pregnancy testing, obviously this was a male lion similar anatomy to some extent."

Mane man once again

Mr Stevenson said some of the park staff came in on their day off to watch the procedure.

Vet nurses helped monitor Leo throughout the procedure. ( Supplied )

Leo made a full recovery and has started leaving little lion presents around his yard.

"He did look a little bit embarrassed for himself," Dr Hick said.

Leo is back on patrol at the zoo.

But Mr Stevenson said it might be a little while before he is able to look his masters in the eyes again.

"Poor Leo was a bit put out by the experience," he said.