Doctors are advising women to take care using menstrual cups, after one user developed temporary kidney problems because the cup was misaligned.
The patient, in her 30s, had been experiencing intermittent pelvic pain and blood in her urine for months, but had not linked the symptoms to the menstrual cup, which is used to catch monthly blood flow.
Although exceedingly rare, a poorly positioned cup inside the vaginal passage can press on other nearby structures, such as ureters - tubes carrying urine to the bladder, according to Danish doctors quoted in the British Medical Journal.
Selecting the appropriate size cup is important, as well as inserting it properly, doctors have stressed.
