Doctors have described the strange case of a woman plagued with worms wriggling in her urine.

The 50-year-old came to hospital complaining that for the past three months she had been passing worms when she went to the toilet.

She was also finding urinating extremely painful and suffering from pain in her side.

Describing her case in the journal BMJ Case Reports, doctors asked her to perform a urine sample.

This revealed multiple small, dark, 0.5cm long larvae clear to naked eye.

Further testing revealed the larvae were not technically worms but belonged to the Dipteria species of fly, known to cause a condition called myasis.

An American woman came to hospital complaining of wriggling worms in her urine. She had no idea how she came to be infested with the parasites, which were revealed to be fly larvae (pictured)

The patient, from South Carolina, was diagnosed immediately with urinary myasis, where a fly lays its eggs in the body and worms infest the urinary tract.

Urinary myasis is generally caught when people drink water sources contaminated with fly eggs.

Other myasis infestations can occur in the skin, eyes, nasal passages and gastrointestinal passage – but urinary myasis is the most uncommon, they said.

Normally, the condition is only seen in developing countries or in people whose immune systems are compromised.

The patient told doctors she had diabetes, which is linked with a compromised immune system with less capacity to fight off infections and parasites.

But doctors noted her condition was well-managed, and there was no blood in her urine.

She had no idea how she came to be infected – but did tell medics she had recently relocated to Charleston, South Carolina, from Mexico, where myasis is more common.

She had not had any procedures involving her genitourinary tract or pelvis, and had not had a catheter – a tube put into the body to drain urine or fluid – put in.

Doctors diagnosed the unnamed 50-year-old with urinary myasis, where a fly lays eggs and these infest a human. Pictured is a worm larvae in a urine sample the patient gave to doctors

As they had never seen an American citizen with urinary myasis before, doctors were forced to consult the medical literature to find out how to treat it.

After researching, they prescribed her ivermectin, a drug used to treat parasites.

A week later the woman reported she had not seen any larvae in her urine - and a camera put into her urinary tract confirmed there were no more larvae.

In light of her case, doctors urged others to consult the medical literature in uncommon cases, as it could lead to better treatment.