Errors in the measurement of endometrial depth using transvaginal sonography in postmenopausal women on tamoxifen: random error is reduced using saline instillation sonography.

OBJECTIVE

The endometrium in women on tamoxifen is often made irregular by small cysts. The aim of this study was to assess the accuracy and precision of the measurement of endometrial depth by transvaginal sonography.

METHODS

The endometrial depth from endometrial biopsies obtained with the resectoscope in 15 women receiving tamoxifen was compared to the endometrial depth measured by TVS. The inter-observer variability was measured in 58 women.

RESULTS

In those biopsies of sufficient quality to allow a measurement, the corresponding depth measurement obtained by ultrasound was up to 3 mm greater than the histological measurement. The interobserver variability for the measurement of endometrial depth using TVS was assessed in 58 postmenopausal women on tamoxifen. The interobserver variability deteriorated as the mean endometrial depth increased, probably because the increase in depth resulted from greater morphological changes within the endometrium such as cyst formation which resulted in an irregular endometrial/myometrial boundary. This may, however, be improved by performing saline instillation sonography. In a prospective study of 10 postmenopausal women, the interobserver variability was significantly greater during tamoxifen treatment compared to pretreatment.

CONCLUSIONS

On the basis of the above, if uterine surveillance using TVS were to be offered to postmenopausal women on tamoxifen, then the procedure should be augmented by saline instillation sonography if the endometrial depth is > 4 mm, as this will improve the measurement precision and also identify intrauterine pathology.