A man has managed to baffle medics after they found a fly buzzing around his intestines.
Doctors in Missouri, US, got more than they bargained for after performing a colonoscopy on the 63-year-old patient.
The bloke had headed into the hospital for a routine colon cancer screening earlier this year.
As we all well know, this involves the rather uncomfortable procedure of putting a camera inside the intestines to have a root around and check everything is hunky dory.
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Everything seemed to be going swimmingly, until doctors spotted something unusual - there was a literal fly on the wall of his intestines.
When they reached his transverse colon, stunned medics noticed the fully intact insect.
There is even photo proof of the fly relaxing inside the bloke's inner workings. It's pretty grim, to be honest.
Despite miraculously making its way deep into the man's body, the fly did not move when it was prodded.
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Experts at the University of Missouri School of Medicine obviously questioned the patient to try and work out how the fly had somehow infiltrated his intestines.
But it has been regarded as a 'mystery', as he has no idea how the insect got inside his body and was completely unaware of it.
The 63-year-old did not suffer from any symptoms and had only consumed clear liquids the day before his colonoscopy, as required to empty the digestive tract.
However, he had eaten a meal of pizza and lettuce on the evening before his 24-hour fast.
Although he didn't recall a fly being in his food, it seems to be the only viable explanation for the bizarre insect saga.
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The doctors said of the case in the American Journal of Gastroenterology: "This case represents a very rare colonoscopic finding.
"[It is a] mystery on how the intact fly found its way to the transverse colon."
In rare cases, humans have unintentionally consumed eggs or larvae laid by flies in fruits or vegetables.
The insects somehow survive the stomach acid and have hatched in the intestines, which is known as intestinal myiasis.
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Matthew Bechtold, the chief of Gastroenterology at the University of Missouri, told The Independent that he suspects it may have entered the bloke's body through his mouth or rear.
He said that because the digestive enzymes and stomach acid should have degraded the fly, it makes it 'less likely' that it was swallowed by the patient.
"If from the bottom, an opening must have been created long enough for the fly to fly undetected into the colon and somehow make its way to the middle part of the colon with no light in a very curvy, large intestine," Bechtold added.
"However, this seems unlikely as well."
The moral of this skin-crawling story - make sure you thoroughly wash your fruit and veg and keep flies away from your backside.
Olivia Burke