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This patient with constipation, pelvic pressure, and an irregularly enlarged uterus likely has a uterine leiomyoma.  Leiomyomas (ie, fibroids) are monoclonal tumors; each fibroid is derived from a distinct progenitor cell.  They can be located on the serosal surface of the uterus (subserosal), within the uterine wall (intramural), and beneath the endometrium (submucosal).

Subserosal fibroids typically cause greater uterine irregularity and enlargement compared to intramural or submucosal fibroids, which are more constrained by uterine tissue.  Because the uterus is located posterior to the bladder and anterior to the rectosigmoid colon, irregular uterine enlargement from fibroids can put pressure on these adjacent organs, causing bulk-related symptoms (eg, pelvic pressure).  Fibroids in the posterior uterus can put pressure on the colon, leading to constipation.

Additional symptoms vary, depending on location.  Anterior subserosal fibroids may cause obstructive urinary symptoms (eg, urgency, incomplete emptying).  Other types (eg, submucosal or intramural) can lead to reproductive difficulties due to distortion of the endometrial cavity.  Submucosal fibroids in particular can cause prolonged and/or heavy menstrual bleeding.

(Choice A)  Adenomyosis typically presents with dysmenorrhea, heavy menstrual bleeding, and a diffusely tender, uniformly globular uterus rather than an irregularly enlarged uterus.  It is not associated with constipation.

(Choice B)  Advanced-stage cervical cancer may cause bulk-related symptoms such as constipation and pelvic pressure.  However, patients typically have abnormal bleeding (eg, postcoital bleeding) or a visible cervical lesion.

(Choice D)  Pelvic organ prolapse is the herniation of pelvic structures through the vagina due to pelvic floor weakening.  Although posterior vaginal wall prolapse (ie, rectocele) can cause pelvic pressure and constipation, it does not cause uterine enlargement.  In addition, premenopausal, nonobese, nulliparous women are at low risk for pelvic organ prolapse.

(Choice E)  Rectovaginal endometriosis, ectopic implants of endometrial glands and stroma, may cause pelvic pain and constipation, especially around menses.  However, dyspareunia (ie, pain with intercourse), dyschezia, and a palpable, tender nodularity are typically present.

Educational objective:
Subserosal uterine leiomyomas (fibroids) can cause irregular uterine enlargement and bulk-related symptoms (eg, pelvic pressure).  Posterior leiomyomas can cause constipation due to pressure on the colon.