ACR Codes: 8.3
Endometrial abnormalities need to be considered in the context of a patient's menstrual life - is the female premenstrual, fertile (menstrual/non-pregnant, pregnant, postpartum), or postmenstrual? Then, the abnormality must be categorized as one of two varieties a) an unusually thick endometrium OR b) a collection spreading the endometrial canal.
In a premenstrual female, endometrial abnormality is very uncommon. If present, it is usually always a collection. The collection may be due, most commonly, to vaginal (colpos)obstruction or, rarely, more proximal uterine (metrocolpos)obstruction. Later in premenstrual life, near the time of menses, blood can accumulate behind an imperforate hymen.
In a menstrual/non-pregnant female, the endometrium cycles and has different appearances at different times during menses. Following menstruation, the thickness of a single layer of endometrium is 0.5 - 1.0 mm. It is a discrete, very thin, hyperechoic line. Between then and the onset of ovulation(proliferative/estrogen phase of the endometrium), the stripe thickens to as much as 8.0 mm. It remains discrete and is uniformly hyperechoic. Note: fertility medications control the number of days in proliferative phase and therefore the thickness of the endometrium. From ovulation to the start of menses (secretory/progesterone phase of the endometrium), there is further thickening of the stripe typically as much as 15.0 mm. The stripe becomes less discrete in this phase, though consistently hyperechoic in echotexture.
In a woman with regular menses, abnormally thick endometrium is easier to ascertain. In a woman with irregular menses, you have no menstrual context for the appearance of the stripe. Thus, 'abnormal' is not so cut and dry. In fertile women, endometrial thickening is concerning for endometrial cancer (though less so than postmenopausal females), endometrial hyperplasia, endometrial polyps, and submucosal fibroids.
The pregnant (or in process of being pregnant) endometrium as well as the post partum endometrium present special issues. Abnormal collections (versus endometrial thickening) comprise the differential for appearance of the pregnancy-prepared or once-pregnant endometrium: a) Miscarriage/Spontaneous abortion, b) Pseudogestational sac of ectopic pregnancy. After miscarriage/spontaneous abortion, evidence of retained products of conception include a gestational sac (with or without a non-living embryo) and a thickened endometrial stripe (EMS) > 5.0 mm. A thinner EMS - < 2.0 mm - favors only retained blood. The pseudogestational sac of ectopic pregnancy is an ill-defined, non-contained collection. Around it is a thin hyperechoic endometrial rim.
The postpartum uterus is not routinely studied, but can be when endometritis is suspected. Typically endometritis is diagnosed clinically, but, in the event an ultrasound is performed, the endometrial canal presents distended. Gas (hyperechoic foci +/- shadowing) may be present.
In a postmenstrual female, a thickened EMS in a woman not on hormone replacement is endometrial cancer until otherwise proven. The differential considerations also include glandular hyperplasia, endometrial polyp(s), and submucosal fibroid.
Endometrial collections are never a normal finding!
Thus, to reiterate - the endometrium must be evaluated in the context of the woman's reproductive stage of life to decide on a differential pathway based on endometrial characteristic - fluid collection within endometrial cavity versus a thickened endometrium.
Finally, hysterosonography is an invaluable tool for evaluation of the endometrium wherein there is an instillation of water into the endometrial canal during a TV sonogram. HSG was critical to the diagnosis in this case.
Reference(s): Berman, Mimi C: Obstetrics and Gynecology, Diagnostic Medical Sonography A Guide to Clinical Practice, Vol 1. JB Lippincott Co, 1991.
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