An endometrial polyp or uterine polyp is a mass in the inner lining of the uterus.^[1] They may have a large flat base (sessile) or be attached to the uterus by an elongated pedicle (pedunculated).^[2][3] Pedunculated polyps are more common than sessile ones.^[4] They range in size from a few millimeters to several centimeters.^[3] If pedunculated, they can protrude through the cervix into the vagina.^[2][5] Small blood vessels may be present, particularly in large polyps.^[2]

They often cause no symptoms.^[4] Where they occur, symptoms include irregular menstrual bleeding, bleeding between menstrual periods, excessively heavy menstrual bleeding (menorrhagia), and vaginal bleeding after menopause.^[3][6] Bleeding from the blood vessels of the polyp contributes to an increase of blood loss during menstruation and blood "spotting" between menstrual periods, or after menopause.^[7] If the polyp protrudes through the cervix into the vagina, pain (dysmenorrhea) may result.^[5]

No definitive cause of endometrial polyps is known, but they appear to be affected by hormone levels and grow in response to circulating estrogen.^[3] Risk factors include obesity, high blood pressure and a history of cervical polyps.^[3] Taking tamoxifen or hormone replacement therapy can also increase the risk of uterine polyps.^[3][8] The use of an intrauterine system containing levonorgestrel in women taking tamoxifen may reduce the incidence of polyps.^[9]

Endometrial polyps can be detected by vaginal ultrasound (sonohysterography), hysteroscopy and dilation and curettage.^[3] Detection by ultrasonography can be difficult, particularly when there is endometrial hyperplasia (excessive thickening of the endometrium).^[2] Larger polyps may be missed by curettage.^[10]

Endometrial polyps can be solitary or occur with others.^[11] They are round or oval and measure between a few millimeters and several centimeters in diameter.^[7][11] They are usually the same red/brown color of the surrounding endometrium although large ones can appear to be a darker red.^[7] The polyps consist of dense, fibrous tissue (stroma), blood vessels and glandlike spaces lined with endometrial epithelium.^[7] If they are pedunculated, they are attached by a thin stalk (pedicle). If they are sessile, they are connected by a flat base to the uterine wall.^[11] Pedunculated polyps are more common than sessile ones.^[4]

Polyps can be surgically removed using curettage with or without hysteroscopy.^[12] When curettage is performed without hysteroscopy, polyps may be missed. To reduce this risk, the uterus can be first explored using grasping forceps at the beginning of the curettage procedure.^[7] Hysteroscopy involves visualising the endometrium (inner lining of the uterus) and polyp with a camera inserted through the cervix. Large polyps can be cut into sections before each section is removed.^[7] The presence of cancerous cells may suggest a hysterectomy (surgical removal of the uterus).^[3] A hysterectomy is usually not considered when cancer is not present.^[7] In either procedure, general anesthetic is typically supplied.^[10]

The effects of polyp removal on fertility has not been studied.^[13]

Endometrial polyps are usually benign although some may be precancerous or cancerous.^[3] About 0.5% of endometrial polyps contain adenocarcinoma cells.^[14] Polyps can increase the risk of miscarriage in women undergoing IVF treatment.^[3] If they develop near the fallopian tubes, they may lead to difficulty in becoming pregnant.^[3] Although treatments such as hysteroscopy usually cure the polyp concerned, recurrence of endometrial polyps is frequent.^[7] Untreated, small polyps may regress on their own.^[15]

Endometrial polyps usually occur in women in their 40s and 50s.^[3] Endometrial polyps occur in up to 10% of women.^[2] It is estimated that they are present in 25% of women with abnormal vaginal bleeding.^[8]

• Cervical polyp
• Uterine fibroids