The warning was issued after an uneven placement obstructed urine flow into the bladder.
Doctors warn that an improperly positioned menstrual cup can cause more than just leakage—it may lead to serious complications, such as uterohydronephrosis, a condition in which a swollen kidney results from blocked urine flow into the bladder. This warning follows a case published in BMJ Case Reports, where a young woman required treatment for the condition.
The report highlights the growing popularity of menstrual cups as a sustainable alternative for managing period blood flow. While complications are rare, the authors note that potential risks include pain, vaginal injuries, allergic reactions, leakage, urinary incontinence, dislodgement of intrauterine devices (IUDs), and infections.
Case Study: A Swollen Kidney Caused by Menstrual Cup Use
The doctors treated a young woman in her early 30s who had noticed blood in her urine and was experiencing intermittent right-sided flank and pelvic pain that had lasted for around 6 months.
Three years earlier, she had had a 9 mm kidney stone removed. And she was using a copper coil for contraception. One or 2 days a month, during the heaviest period blood flow, she used a menstrual cup which she emptied every 2–3 hours.
A scan revealed no signs of kidney stones, but it did show a swollen right kidney and ureter—the tube that carries urine away from the kidneys. It also showed a menstrual cup positioned right next to the opening of the ureter into the bladder (ureteral ostium).
The woman was asked not to use the menstrual cup during her next period and to return for a follow-up scan a month later. The scan showed that the swelling had gone down and that urine was draining normally from both kidneys.
The woman’s symptoms had cleared up completely, prompting the report authors to conclude that the cup had obstructed the flow of urine from the right ureter.
When the woman attended for a further check-up six months later, she said that she had only used the menstrual cup occasionally for 3–4 hours at a time during visits to a swimming pool. She hadn’t wanted to use the cup regularly again, for fear of possible complications.
Limited Research on Similar Cases
“To our knowledge, only a few similar cases have previously been reported. [These] cases were similar to our case,” note the report authors.
“In all cases except one, a follow-up [computed tomography scan] or ultrasound was performed which showed regression of the ureterohydronephrosis. In three cases, the women resumed use of the menstrual cup, and none of them experienced resumption of symptoms (unknown follow-up periods). One of them chose a smaller sized cup,” they write.
Women (and clinicians) need to be better informed about the correct use (and potential complications) of menstrual cups, suggest the report authors.
“When the terminal part of the ureters passes into the bladder, they are in close proximity to the vagina, which can affect urinary drainage from the ureter. Correct positioning, along with choosing the correct cup shape and size, is important to prevent negative effects on the upper urinary tract,” they explain.
“Presently, menstrual cups can be bought and used without clinical advice from a health professional, which emphasizes the importance of detailed and clear patient information material,” they add.
Reference: “Ureterohydronephrosis due to a menstrual cup” by Clara Maarup Prip and Lotte Kaasgaard Jakobsen, 1 January 2025, BMJ Case Reports CP.
DOI: 10.1136/bcr-2024-262035
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