Adenomyosis (Endometriosis Interna)
The most probable diagnosis is adenomyosis (endometriosis interna), given the classic presentation of menorrhagia and pelvic pain with a symmetrically enlarged, diffusely abnormal uterus without discrete masses on ultrasound. 1, 2
Clinical Reasoning
The key diagnostic features pointing to adenomyosis include:
Symmetrically enlarged uterus without nodularity or discrete mass - This is the hallmark imaging finding that distinguishes adenomyosis from leiomyomas, which typically present as focal masses or cause asymmetric uterine enlargement 2, 3
Menorrhagia as the predominant symptom - Heavy menstrual bleeding is the most common presenting complaint in adenomyosis, occurring in approximately 80% of patients with internal adenomyosis 2, 4
Associated pelvic pain - While pain symptoms occur in both adenomyosis phenotypes, the combination with heavy bleeding strongly suggests internal adenomyosis 4
History of prior pregnancy - Increasing parity is a recognized risk factor for developing adenomyosis, and internal adenomyosis specifically is more common in parous women 2, 4
Why Other Diagnoses Are Less Likely
Intramural leiomyoma (option d) would typically present with focal nodularity or an identifiable mass on ultrasound, not symmetric diffuse enlargement 1
Endometrial hyperplasia (option b) causes abnormal bleeding but does not produce symmetric uterine enlargement; it affects only the endometrial lining 1
Chronic endometritis (option c) presents with pain and bleeding but does not cause the characteristic symmetric uterine enlargement seen here 1
External endometriosis (option e) occurs outside the uterus and would not cause symmetric uterine enlargement; it is more common in younger, nulliparous women with associated deep infiltrating disease 4, 1
Diagnostic Confirmation
If further imaging is needed beyond the initial ultrasound, MRI pelvis with diffusion-weighted imaging would be the next appropriate step to definitively characterize the adenomyosis and assess for coexisting pathology 1, 5
Transvaginal ultrasound findings specific to adenomyosis include echogenic nodules and striations radiating from the endometrium, myometrial cysts, heterogeneous myometrium with blurring of the endometrial border, and globular uterine enlargement 3
Clinical Context
Adenomyosis represents ectopic endometrial glands within the myometrium, causing muscular hyperplasia and hypertrophy that produces the characteristic diffuse, symmetric enlargement 2, 3. Internal adenomyosis (affecting the inner myometrium and junctional zone) is the specific phenotype most strongly associated with heavy menstrual bleeding, distinguishing it from external adenomyosis which more commonly presents with endometriosis 4