A woman in her thirties was hospitalized after developing severe flank pain and urinary symptoms that were eventually linked to the position of a menstrual cup, according to a case published in BMJ Case Reports.1
The patient sought medical care after experiencing repeated episodes of pain on one side of her lower back along with blood in her urine. Doctors initially considered common causes such as kidney stones. However, imaging studies later identified swelling in the ureter and kidney caused by a blockage associated with the menstrual cup’s placement.
After the device was removed, the patient’s symptoms resolved and follow-up imaging confirmed that the obstruction had cleared.
The patient presented with intermittent flank pain and hematuria, which refers to the presence of blood in urine. To determine the cause, clinicians performed CT urography, an imaging technique used to evaluate the urinary tract.
The scan showed dilation of the ureter and kidney on the affected side, a condition known as ureterohydronephrosis. Doctors also observed that the menstrual cup was positioned toward the right side of the vaginal canal near the opening of the ureter into the bladder.
This positioning created pressure on the ureter, preventing normal urine flow from the kidney to the bladder. When the menstrual cup was removed, the mechanical compression resolved and the patient’s symptoms improved.
Menstrual cups are reusable devices made from medical-grade silicone, rubber, or elastomer. They are inserted into the vagina to collect menstrual blood rather than absorb it.
Most manufacturers recommend emptying and cleaning the cup every 4 to 12 hours depending on menstrual flow. Many users choose menstrual cups because they are reusable and produce less waste compared with disposable menstrual products.
When placed correctly, the cup sits below the cervix and forms a seal with the vaginal walls to prevent leakage.
The ureters are tubes that carry urine from the kidneys to the bladder. Before entering the bladder, each ureter runs close to structures in the pelvis, including the vaginal wall.
If a menstrual cup is positioned too far to one side or placed incorrectly, it may press against nearby tissues. In rare cases, this pressure can compress the ureter and obstruct urine flow. When urine cannot drain normally, it may accumulate in the ureter and kidney, causing swelling known as hydronephrosis.
The BMJ report notes that such complications are uncommon but clinically significant because delayed diagnosis may lead to kidney injury.
Menstrual cups are widely regarded as safe menstrual hygiene products. Studies and clinical reviews indicate that most users experience no major health issues.
However, medical literature has described a small number of complications. These include vaginal irritation, allergic reactions, leakage, and in rare cases displacement of intrauterine contraceptive devices. Very uncommon reports have also described toxic shock syndrome and urinary tract complications.
The case described in the BMJ report adds to a limited number of documented instances where menstrual cup placement affected the urinary system.1
Researchers say both healthcare professionals and menstrual cup users should be aware of symptoms that may indicate a problem. Persistent flank pain, pelvic discomfort, or blood in urine during menstruation should prompt medical evaluation.2
Education on proper insertion techniques and selecting the appropriate cup size may reduce the risk of incorrect placement. Clinicians may also consider menstrual cup positioning as a possible factor when evaluating unexplained urinary symptoms in menstruating patients.
Although such complications remain rare, the reported case highlights the importance of correct use and awareness as menstrual cups continue to be used by millions of people worldwide.
1. Coutinho, Mariana, Joana Oliveira, and Luís Guimarães. 2025. “Ureterohydronephrosis Due to Misplaced Menstrual Cup.” BMJ Case Reports 18 (2): e262035. https://casereports.bmj.com/content/18/2/e262035.
2. BMJ Group. 2025. “Raising Awareness of a Rare but Serious Risk Linked to Menstrual Cup Use.” BMJ Group. https://bmjgroup.com/raising-awareness-of-a-rare-but-serious-risk-linked-to-menstrual-cup-use/.
(Rh/SS/MSM)