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 visualisation for confirmation.
The prevalence of endometrial polyps increases with age and ranges from 7.8-34.9% ref. Endometrial polyps are frequently seen in patients receiving tamoxifen.
Most polyps are asymptomatic although they can be a common cause of post-menopausal bleeding (can account for approximately 30% of cases 5). In pre-menopausal women, they may cause intermenstrual bleeding, metrorrhagia, and infertility.
Polyps can be histologically characterised as localised 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
2-4% of "benign" polyps with have a small focus of cancer within them.
There may be a predilection towards the fundal and cornual regions within the uterus. They can be multiple in ~20% of cases.
Although endometrial polyps may be visualised at transvaginal ultrasound as non-specific endometrial thickening, they may also be identified as focal masses within the endometrial canal.
- a stalk to the polyp may either be thin- or broad-based
- a single feeding vessel may be seen extending to the polyp on colour Doppler imaging 7
- Visualisation of a vascular pedicle is 76% sensitive and 95% specific for endometrial polyps 7
- cystic spaces corresponding to dilated glands filled with proteinaceous fluid may be seen within the polyp and is considered a relatively characteristic feature 3
- may appear as just diffusely thickened endometrium, without visualisation of a discrete mass (mimicking endometrial hyperplasia)
- may show flow within the stalk
- 3D ultrasound may be useful to help delineate the borders of a polyp
Although not always necessary for a diagnosis, polyps are well-characterised on sonohysterography and appear as echogenic, smooth, intracavitary masses outlined by the fluid. The typical appearance of an endometrial polyp at sonohysterography is as 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.
Treatment and prognosis
Most polyps are benign and may be treated with a polypectomy, if symptomatic.
A very small percentage (0.5-3%) of polyps may contain endometrial carcinoma 4.
Entities that can potentially mimic an endometrial polyp include:
- uterine leiomyoma(s): especially if pedunculated and submucosal, although most leiomyomas tend to be hypoechoic on ultrasound and demonstrate hypointense signal on MRI
- foci of endometrial hyperplasia
- endometrial carcinoma
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. Gupta A, Desai A, Bhatt S. Imaging of the Endometrium: Physiologic Changes and Diseases: Women's Imaging. (2017) Radiographics : a review publication of the Radiological Society of North America, Inc. 37 (7): 2206-2207
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