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Endometrial thickness

Endometrial thickness is a commonly measured parameter on routine gynaecological ultrasound and MR imaging. The appearance as well as the thickness of the endometrium will depend on whether the patient is of reproductive age or post-menopausal and, if of reproductive age, at what point in the menstrual cycle they are examined. This article provides normal ranges for endometrial thickness.

Radiographic features

Ultrasound (endovaginal)

The endometrium should be measured in the long axis or sagittal plane. The measurement is of the thickest echogenic area from one basal endometrial interface across the endometrial canal to the other basal surface. Care should be taken not to include the hypoechoic myometrium in this measurement.

The normal endometrium changes in appearance as well as in thickness throughout the menstrual cycle.  

  • in the menstrual and early proliferative phase it is a thin, brightly echogenic stripe comprising of the basal layer (Figure 1)
  • in the late proliferative phase it develops a trilaminar appearance: outer echogenic basal layer, middle hypoechoic functional layer, and an inner echogenic stripe at the central interface (Figure 2)
  • in the secretory phase it is at its thickest and becomes uniformly echogenic, as the functional layer becomes oedematous and isoechoic to the basal layer (Figure 3).


The postmenopausal endometrium should be smooth and homogeneous.

Normal range

Commonly accepted endovaginal ultrasound values are as follows:

Premenopausal

In premenopausal patients there is significant variation by stage of the menstrual cycle.

  • during menstruation 1,4: 2-4 mm
  • early proliferative phase (day 6-14): 5-7 mm
  • late proliferative-pre ovulatory phase: up to 11 mm
  • secretory phase: 7-16 mm
  • following dilatation and curettage or spontaneous abortion: <5 mm, if it is thicker consider retained products of conception.

Postmenopausal

Will depend on the use of use of hormonal therapy / tamoxifen

  • if on no medication 5: <5 mm
    • if there is vaginal bleeding, the risk of carcinoma is ~7% if endometrium is >5 mm 8
    • if there is no bleeding, the risk of carcinoma is ~7% if the endometrium is >11 mm 8
  • if on hormonal therapy 6: upper limit is 8-15 mm 
  • if on tamoxifen 3: <6 mm (although ~50% of those receiving tamoxifen have been reported to have thickness of >8 mm 7)

See also


Related articles

Ultrasound

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