The endometrium is the mucosal lining of the uterine cavity that undergoes cyclical changes in response to the hormones estrogen and progesterone during the menstrual cycle. In the proliferative phase, the endometrium thickens under the influence of estrogen, and in the secretory phase after ovulation, it becomes thicker and more glandular in preparation for embryo implantation. On transvaginal ultrasound, the endometrium changes in both thickness and echogenicity throughout the cycle, and these predictable changes allow sonographers to assess whether the endometrium appears normal for the patient’s phase of the cycle. Evaluating the endometrium is a key component of every pelvic ultrasound examination.
Sonography Term