An 18-year-old woman comes to the office due to lower abdominal pain that radiates to her lower back and thighs during menses. The patient had no pain while on oral contraceptives but stopped taking them 5 months ago due to unscheduled breakthrough bleeding. Menstrual periods now occur every 30 days with 5 days of bleeding. The pain and bleeding are worse on the second day, requiring the patient to change her pad every 4 hours. She also has nausea and fatigue during the first 2 days of menses. The patient is sexually active with a male partner and uses condoms inconsistently. She has no intermenstrual bleeding or pain with intercourse. Vital signs are normal. BMI is 19.5 kg/m². Pelvic examination reveals a small, mobile uterus and no palpable adnexal masses. Which of the following is the most likely diagnosis in this patient?

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11ec25c8_d9b5_7ee9_bc81_8f7becc1d045_MD0003_00 This patient, who had resumption of ovulation after discontinuing oral contraceptive use, now has increased painful lower abdominal cramping associated with menses, suggestive of primary dysmenorrhea. Primary (ie, physiologic) dysmenorrhea (painful menses) is common, particularly among adolescents. Excessive prostaglandin production during menses can stimulate uterine contractions and result in lower abdominal pain that can radiate to the back and thighs. Some patients may also develop gastrointestinal symptoms (eg, nausea, vomiting, bloating, diarrhea) from prostaglandin-induced gastrointestinal stimulation. Symptoms are typically worse during the first few days of menses and can interfere with daily activities. Patients have a normal pelvic examination because the pelvic pain occurs without an identifiable pathologic cause. The first-line treatment for primary dysmenorrhea is nonsteroidal antiinflammatory drugs (NSAIDs), which reduce prostaglandin synthesis. For patients who are sexually active or in whom NSAIDs are ineffective or cannot be tolerated, combination oral contraceptives (COCs) can be used. Although this patient previously had unscheduled breakthrough bleeding as a side effect of COCs, she can be prescribed another formulation that limits this side effect. (Choice A) Adenomyosis can cause painful menses; however, this diagnosis is less likely because this patient does not have a tender, symmetrically enlarged (ie, "globular") uterus. Adenomyosis (Choice B) Endometriosis is a common cause of painful menses. However, patients often have additional pain during urination (dysuria), bowel movements (dyschezia), and sexual activity (dyspareunia). In contrast to this patient, those with endometriosis often have a fixed, immobile uterus or adnexal masses due to the ectopic endometrial glands and stroma. (Choice C) Intermittent ovarian torsion can cause lower abdominal pain and nausea; however, patients typically have an adnexal mass, and symptoms are not confined to the menstrual period. (Choice D) Pelvic congestion syndrome typically presents as a dull, ill-defined pelvic ache that worsens with intercourse or during long periods of standing. In contrast to this patient, those with pelvic congestion syndrome have pain prior to menses that is then relieved by menses. (Choice F) Uterine leiomyoma can cause pelvic pain secondary to bulk symptoms. Most patients have heavy, prolonged menses (eg, soaking a pad every 1-2 hours, passage of clots) and an enlarged, irregular uterus. Educational objective: Patients with primary dysmenorrhea have cyclic, lower abdominal pain during menses and a normal pelvic examination. First-line treatment is with nonsteroidal anti-inflammatory drugs. References: Nonsteroidal anti-inflammatory drugs for dysmenorrhoea. (http://www.ncbi.nlm.nih.gov/pubmed/26224322) Diagnosis and initial management of dysmenorrhea. (http://www.ncbi.nlm.nih.gov/pubmed/24695505)

An 18-Year-Old Woman Comes to the Office Due to Lower