A Czech woman went to the hospital after suffering from severe stomach pain, only for doctors to discover a huge parasite in her kidneys, which eventually led to her death, Central European News reported.

Hana Foldynova, 76, was admitted to the Krnov Hospital in northeastern Czech Republic after her general practitioner discovered blood in her urine. Doctors thought it was a blood clot, but when they went in for surgery, they were shocked to discover a blood-red, 3.9 inch-long parasite living in one of her kidneys.

To make matters worse, a second, 2.4-inch-long worm had crawled into her bladder. Doctors removed both worms.

“When patients have blood in their urine, it is usually caused by some kidney stone, inflammation or cancer. But this was very surprising for us,” urologist Dr. Jan Pulcer told Czech media.

The parasite in her kidney was identified as a giant kidney worm, called Dioctophyme renale, that is not uncommon in dogs but extremely rare in humans. Surgery is the only method of removal; if left, it will destroy the kidney it inhabits.

The worm weaked Foldynova, and doctors said she was unable to recover after they removed it from her body.

Both parasitic worms were sent to National Laboratory in Prague to confirm the diagnosis.

It’s unclear how the parasite entered Foldynova’s body, as the usual method is by eating badly cooked fish, Dr. Ivo Odstrcil, head urologist at Krnov Hospital, told CEN.

“Her family have said that she liked local seafood. We assume that she was infected after she had eaten badly cooked fish,” Odstrcil said.

A giant kidney worm can live in the human body up to five years, according to scientific literature, reported CEN. Human infestation is extremely rare, and the current case is the first and only one recorded in the Czech Republic.