Woman in her 30s develops kidney infection from ill-fitting menstrual cup; how to prevent it

An ill-fitting menstrual cup landed a woman in her 30s with a kidney infection after it blocked her urine flow. Unaware of the secret culprit, the woman started experiencing symptoms like blood in her urine as well as intermittent pelvic pain for around six months, before she decided to see a doctor. Since the woman had a kidney stone removed three years earlier, her guess was that the symptoms could be connected to that.

The woman had been using a menstrual cup to catch blood during the days of her heaviest period flow, which she emptied every two to three hours.

A scan finally disclosed the root cause of the woman's symptoms. To the woman's surprise the scan didn't show any kidney stones, but revealed a swollen right kidney and ureter — the tube that carries urine away from the kidneys. Her menstrual cup could also be seen on the scan, which was right next to the opening of the ureter into the bladder.

The woman was subsequently told not to use the menstrual cup and do a follow-up scan a month later.

Her symptoms disappeared when she met the doctors for a follow-up, which led the doctors to conclude it was a menstrual cup that caused the kidney trouble.

The case was detailed in the journal BMJ and highlights the importance of the correct size and shape of the cup to prevent negative impact on the upper urinary tract.

A menstrual cup is a small, flexible cup that is inserted into the vagina to catch and collect the period flow. It works differently than a tampon or pad which absorbs the menstrual flow. After every few hours, the cup can be removed and washed for reuse, which also makes them eco-friendly.

"Presently, menstrual cups can be bought and used without clinical advice from a health professional, which emphasises the importance of detailed and clear patient information material," said the study authors.

The study authors mentioned that there are three other cases where women kept using menstrual cups after getting advice on positioning and choosing a smaller size, and they didn't have any problems again.

‘Correct positioning, along with choosing the correct cup shape and size, is important to prevent negative effects on the upper urinary tract,’ the authors said.

How to choose the correct menstrual cup size

Age and childbirth history: Many brands offer a smaller size for younger users (typically under 30) or those who haven’t given birth vaginally, and a larger size for those over 30 or who have given birth vaginally.

Cervix height: If you have a low cervix (measured by inserting a clean finger to see how far it reaches), a shorter cup is ideal. A high cervix allows for a longer cup.

Flow intensity: A larger cup may be better for heavy flow, while a smaller one can work for light to moderate flow.

Pelvic floor strength: If you have strong pelvic muscles (e.g., from Kegel exercises), a firmer cup may stay in place better, while a softer cup is more comfortable for those with weaker muscles.

(Picture courtesy: iStock)