CBS Local —┬áDoctors in Japan made a startling discovery inside a woman who had been troubled with stomach pain and bloating. Surgeons found two surgical sponges that had been left in the patient for at least six years.

According to a Feb. 21 report in The New England Journal of Medicine, the 42-year-old woman went to doctors after experiencing bloating in her lower abdomen for three years. The patient, who had been through two C-sections after both her pregnancies, was given a CT scan which uncovered the two “hyperdense, stringy structures” near each of the mother’s hips.

Doctors reportedly believe that the sponges were left in the woman during one of the two C-sections, which were performed six and nine years ago. “The patient received two C-sections in the same gynecologic clinic,” Dr. Takeshi Kondo said, via CNN. “Although she met the surgeon and told him (about) the retained foreign bodies, the surgeon did not admit his mistake on the grounds of lack of clear proof.”

The 42-year-old’s symptoms quickly went away after the sponges were taken out. According to a 2013 medical review, the chance that a medical instrument is accidentally left inside a patient is between one-in-5,500 and one-in-18,760. The review also called such incidents a “never event,” meaning it should never take place during any operation.