If you're having a bad day, spare a thought for Mr Flea.

A 300 gram ball of gunk known as a 'urethral bean' has been removed from the horse's penis by a Queensland vet.

Displaying the type of enthusiasm known only to rural vets after such a find, Tess Salmond, from Clermont, said her colleagues around the country had been shocked and impressed by the size of the monster bean.

"It's basically this big, huge ball of smegma. That's a waxy substance that includes dirt, skin cells and secretions and it builds up," Dr Salmond explained.

"It was just a routine examination when the horse had been sedated to have its teeth checked, and we just check to see if they've got one of these and I struck the mother lode.

"It's the size of a mandarin."

In fact, some of her fellow rural vets who have seen pictures of the bean on social media believe it might be the biggest ever found.

"I've been getting lots of messages from vet colleagues around the state. It's certainly the biggest they've ever seen," Dr Salmond said.

"A vet specialist down in New South Wales jokingly said I should call the Guinness World Records, but I don't think it's something they measure.

"But it certainly is a monster by most standards, that's for sure."

Mr Flea is very relieved his appendage has been cleared of the 300 gram urethral bean. ( Supplied )

Dr Salmond said the horse was no doubt relieved after the bean's removal.

She said if left untreated, the blockage could have had serious consequences.

"If it does get big enough it can restrict the outflow of urine, which of course is a huge medical emergency," she said.

"[This bean] grew out to the side rather than over the urethra, so it was a very lucky horse."

Mr Flea will be checked more regularly in the future to ensure the problem does not arise again.

"We'd just advise more regular checking as he obviously gets more of a build up than most," Dr Salmond said.

"But it does have to happen under sedations because, as you can imagine, pulling something that size out of a penis can be quite ouchy.

"I think he walked away with a spring in his step, there's no doubt about that."