Doctors from Missouri encountered an unusual phenomenon, which is described in detail in the American Journal of Gastroenterology. A 63-year-old man undergoing screening for colon cancer was the subject of an unprecedented case. During a colonoscopy, specialists discovered that a fly was living in the patient’s intestines.

This case was described as a “very rare colonoscopic finding” in medical practice. Doctors cannot explain how the fly got inside the patient and developed in his intestines, especially considering that the day before the colonoscopy the man consumed only clear liquid, as recommended by the doctor.

Interestingly, even with this diet, the patient does not remember eating any food containing flies.

Although the patient only consumed clear liquids before his procedure and, two days before, he had eaten pizza and lettuce – but could not recall a fly being on any of the food he ate.

He had no symptoms to suggest he had ingested it. Doctors discovered that the fly, which remained intact, somehow survived the stomach acid and continued to live inside the transverse colon.

The fly was not showing any activity when it was discovered, but photographs taken during the procedure clearly show its presence, surprising the researchers.

Matthew Bechtold, the chief of Gastroenterology at the University of Missouri, told The Independent that he and other doctors prodded the fly and confirmed it was dead.

Insects can deposit eggs onto food, which is then consumed by a human and, in rare cases, survive stomach acid and the gastrointestinal environment, according to the National Library of Medicine.