Urogenital Imaging

Polyp, endometrial

localized overgrowth of endometrial glands and stroma that project beyond the surface of the endometrium. They are soft and pliable, and may be single or multiple. Most polyps arise from the fundus of the uterus. Endometrial polyps vary from a few mm to several cm in diameter, and it is possible for a single large polyp to fill the endometrial cavity. Endometrial polyps may have a broad base (sessile) or be attached by a slender pedicle (pedunculated). The peak incidence is between the ages of 40 and 49. Endometrial polyps are noted in approximately 10% of women when the uterus is examined at autopsy. The aetiology of endometrial polyps is unknown.

Because polyps are often associated with endometrial hyperplasia, unopposed oestrogen may be the cause. The majority of endometrial polyps are asymptomatic. Those that are symptomatic are associated with a wide range of abnormal bleeding patterns. Occasionally a pedunculated endometrial polyp with a long pedicle may protrude from the external cervical os. Recently, unusual polyps have been described in association with chronic administration of the anti-oestrogen tamoxifen.

At ultrasound, an endometrial polyp appears as a well-defined hyperechoic mass, usually less that 2 cm in diameter, in the endometrial cavity. Transvaginal ultrasound is preferred to transabdominal ultrasound (Fig.1). A large polyp may be recognized on CT as an intracavitary filling defect in the uterus, but CT is not the optimal imaging modality for endometrial polyps. On MRI, T1-weighted images demonstrate endometrial polyps as intracavitary filling defect of medium signal intensity, similar to the signal intensity of normal endometrium. On T2-weighted scans polyps may image with signal intensity similar to or slightly lower than the endometrium, and they may be seen to cause widening of the endometrial cavity (Fig.2). Endometrial polyps enhance after intravenous gadolinium. Occasionally polyps may prolapse through the cervix. Malignant transformation of an endometrial polyp has been estimated to be as high as 0.5%. The management of endometrial polyps is removal by curettage or via the hysteroscope. Because of the frequent association of endometrial polyps and other endometrial pathology, it is important to examine histologically both the polyp and the associated endometrial lining. In indeterminate cases, sonohysterography may be used prior to biopsy to distinguish endometrial polyps and endometrial hyperplasia. Polyps, because of the mobility, often tend to elude their curette.

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Fig.1

Transvaginal ultrasound image showing a uterine polyp (arrow).

Polyp, endometrial, Fig.1		Polyp, endometrial, Fig.2