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Endometrial polyps are benign nodular protrusions of the endometrial surface, and one of the entities included in a differential of endometrial thickening. Endometrial polyps can either be sessile or pedunculated. They can often be suggested on ultrasound or MRI studies but may require sonohysterography or direct visualization for confirmation.
The prevalence of endometrial polyps increases with age and ranges from 7.8-34.9% 8. Endometrial polyps are frequently seen in patients receiving tamoxifen. Other risk factors include foreign bodies, multiparity, chronic cervicitis and estrogen secretion.
Most polyps are asymptomatic although they can be a common cause of postmenopausal bleeding (can account for ~30% of cases 5). In pre-menopausal women, they may cause intermenstrual bleeding, metrorrhagia, and infertility.
Polyps can be histologically characterized as localized hyperplastic overgrowths of glands and stroma. They consist of irregularly-distributed endometrial glands and stroma and generally consist of three components:
- a stroma of focally or diffusely dense fibrous or smooth muscle tissue
- thick-walled vessels
- endometrial glands
0.8-4.8% of endometrial polyps are premalignant or malignant 9.
- there is a predilection towards the fundal and cornual regions within the uterus
- they can be multiple in ~20% of cases
- rarely protrude into the endocervical canal or through the cervical os
The best time of examination for endometrial polyp is postmenstrual.
- usually solitary homogeneous and echogenic lesion
- interrupted mucosa sign 10: the endometrial polyp focally interrupt the normal mucosal contour of the uterine cavity
- it is rarely hypoechoic or heterogeneous
- a stalk to the polyp may either be thin- (i.e. pedunculated) or broad-based
- the bright edge sign 11: the appearance of one or two well-defined short echogenic linear echoes at the polyp borders which are perpendicular to the ultrasound beam
- may appear isoechoic as a focal non-specific thickened endometrium, without visualization of a discrete mass
- rarely appears as diffuse endometrial thickening as the endometrial polyp fills the endometrial cavity, mimicking endometrial hyperplasia
- rarely cystic spaces could be seen corresponding to dilated glands filled with proteinaceous fluid within the polyp 3
- maybe surrounded by endometrial fluid
pedicle artery sign: a single feeding vessel may be seen extending to the polyp on color Doppler imaging 7
- visualization of a vascular pedicle is 76% sensitive and 95% specific for endometrial polyps 7
- 3D ultrasound may be useful to help delineate the borders of a polyp
Although not always necessary for a diagnosis, polyps are well-characterized on sonohysterography and appear as echogenic, smooth, intracavitary masses outlined by the fluid. The typical appearance of an endometrial polyp at sonohysterography is a well-defined, homogeneous, polypoid lesion that is isoechoic to the endometrium with preservation of the endometrial-myometrial interface 5. There is usually a well-defined vascular pedicle within the stalk.
Signal characteristics include:
- T1: often isointense signal to endometrium
- T2: endometrial polyps are often seen as hypointense intracavitary masses surrounded by hyperintense fluid and endometrium
- T1 C+ (Gd): can show either homogeneous or heterogeneous enhancement
Polyps may be seen as pedunculated or sessile filling defects within the uterine cavity. This is not a preferred method for evaluation compared with the other modalities.
- prolapse: prolapsed endometrial polyp
- a very small percentage (0.5-3%) of polyps may contain endometrial carcinoma 4.
Treatment and prognosis
Most polyps are benign and may be treated with a polypectomy, if symptomatic.
Entities that can potentially mimic an endometrial polyp include:
- uterine leiomyoma(s): especially if submucosal and pedunculated, although most leiomyomas tend to be hypoechoic on ultrasound and demonstrate hypointense signal on MRI
- foci of endometrial hyperplasia
- endometrial carcinoma
- intrauterine blood clot
For hyperechoic content within the endometrium also consider:
- 1. Grasel RP, Outwater EK, Siegelman ES et-al. Endometrial polyps: MR imaging features and distinction from endometrial carcinoma. Radiology. 2000;214 (1): 47-52. Radiology (full text) - Pubmed citation
- 2. Nalaboff KM, Pellerito JS, Ben-levi E. Imaging the endometrium: disease and normal variants. Radiographics. 21 (6): 1409-24. Radiographics (full text) - Pubmed citation
- 3. Hulka CA, Hall DA, Mccarthy K et-al. Endometrial polyps, hyperplasia, and carcinoma in postmenopausal women: differentiation with endovaginal sonography. Radiology. 1994;191 (3): 755-8. Radiology (abstract) - Pubmed citation
- 4. Jorizzo JR, Chen MY, Riccio GJ. Endometrial polyps: sonohysterographic evaluation. AJR Am J Roentgenol. 2001;176 (3): 617-21. AJR Am J Roentgenol (full text) - Pubmed citation
- 5. Davis PC, O'neill MJ, Yoder IC et-al. Sonohysterographic findings of endometrial and subendometrial conditions. Radiographics. 22 (4): 803-16. Radiographics (full text) - Pubmed citation
- 6. Machtinger R, Korach J, Padoa A et-al. Transvaginal ultrasound and diagnostic hysteroscopy as a predictor of endometrial polyps: risk factors for premalignancy and malignancy. Int. J. Gynecol. Cancer. 15 (2): 325-8. doi:10.1111/j.1525-1438.2005.15224.x - Pubmed citation
- 7. Akshya Gupta, Amit Desai, Shweta Bhatt. Imaging of the Endometrium: Physiologic Changes and Diseases: Women’s Imaging. (2017) RadioGraphics. doi:10.1148/rg.2017170008
- 8. Salim S, Won H, Nesbitt-Hawes E et-al. Diagnosis and management of endometrial polyps: a critical review of the literature. (2011) Journal of minimally invasive gynecology. 18 (5): 569-81. doi:10.1016/j.jmig.2011.05.018 - Pubmed
- 9. Tabrizi AD, Vahedi A, Esmaily HA. Malignant endometrial polyps: Report of two cases and review of literature with emphasize on recent advances. (2011) Journal of research in medical sciences : the official journal of Isfahan University of Medical Sciences. 16 (4): 574-9. Pubmed
- 10. Aya Kamaya, Pauline Chang Yu, Carla Ramas Lloyd, et-al. Sonographic Evaluation for Endometrial Polyps. (2016) Journal of Ultrasound in Medicine. 35 (11): 2381. doi:10.7863/ultra.15.09007 - Pubmed
- 11. B. Caspi, Z. Appelman, R. Goldchmit, et-al. The bright edge of the endometrial polyp. (2000) Ultrasound in Obstetrics and Gynecology. 15 (4): 327. doi:10.1046/j.1469-0705.2000.00096.x - Pubmed