A 24-year-old woman arrives in the emergency department (ED) at 2 a.m. pale, diaphoretic, and curled on her side with severe lower abdominal pain and vomiting. Her menstrual period started earlier that day. This is her third ED visit in a year for similar symptoms. Laboratory results are normal, β-hCG is negative, and pelvic ultrasound shows only a small hemorrhagic cyst. For many emergency physicians, this scenario is familiar—and frustrating. Yet it reflects one of the most common and persistently missed clinical patterns in emergency medicine: endometriosis.

Endometriosis is a chronic, estrogen-dependent inflammatory disease characterized by endometrial-like tissue outside the uterus, commonly involving the ovaries, uterosacral ligaments,

bowel, bladder, and, more rarely, the thorax.¹ It is not simply “bad periods,” but a systemic inflammatory condition capable of causing severe, disabling pain that often mimics surgical emergencies. It affects approximately 10 percent of people of reproductive age, yet the average diagnostic delay remains seven to 10 years.² During that interval, many patients present repeatedly to EDs with severe pelvic pain and receive labels such as dysmenorrhea, ovarian cysts, irritable bowel syndrome, or anxiety—diagnoses that often obscure the underlying disease.

For emergency physicians, the goal is not to make a definitive diagnosis in the ED. Rather, the task is to recognize a high-probability clinical pattern, exclude time-sensitive emergencies, and initiate management that improves the patient’s diagnostic and therapeutic trajectory.

Why Patients with Endometriosis Present to the Emergency Department

Patients with endometriosis often present to the ED because pain escalates rapidly and unpredictably. Inflammatory flares may produce symptoms that resemble ovarian torsion, appendicitis, bowel pathology, or other urgent conditions. Severe pelvic pain, nausea, vomiting, and visible physiologic distress are common. Particularly early in the disease course, patients themselves may be unable to distinguish a flare from other acute emergencies, prompting repeated visits.

Delayed access to gynecologic care, fragmented outpatient management, and long waits for subspecialty assessment leave many patients without a coherent longitudinal plan.³ When ED visits are framed merely as “chronic pain,” patients often leave without direction and return when symptoms recur. By contrast, when clinicians explain that emergent conditions have been excluded and that the clinical pattern is concerning for endometriosis, patients leave with a more meaningful explanation and a clearer next step.

When to Suspect Endometriosis in the Emergency Department

In the ED, endometriosis should be suspected in patients with recurrent severe cyclical pelvic pain, particularly when investigations are reassuring. Severe dysmenorrhea beginning in adolescence is an important clue, especially when patients describe periods that have “always been terrible” or substantially worse than those of peers. Progression is particularly helpful diagnostically: pain that begins as one or two difficult days each cycle, then extends over more days, occurs outside menstruation, and eventually becomes more persistent.³

Ask directly about dyspareunia and about bowel or bladder symptoms that fluctuate with the menstrual cycle. Cyclical dyschezia, rectal pain, tenesmus, dysuria, urgency, hematuria, and hematochezia all increase suspicion. These features not only strengthen the pretest probability of endometriosis but may also suggest deeper infiltrating disease and greater risk of complications.⁴ Thoracic symptoms that track with menses, such as cyclical chest pain, cough, dyspnea, hemoptysis, or shoulder-tip pain, should also raise concern for extrapelvic involvement.⁵ A key pitfall is that physical examination and basic ED investigations are often normal during flares. That apparent normality is exactly where clinicians may prematurely close the diagnostic process.

A useful bedside framing is this: severe cyclical pelvic pain with reassuring investigations should be considered possible endometriosis until proven otherwise. This does not require the emergency physician to declare a definitive diagnosis. It simply means recognizing a high-probability pattern and avoiding repeated dismissal of a disease that is common, morbid, and frequently missed.

Distinguishing Flare from Complication

Although most ED presentations represent inflammatory flares rather than true complications, a small but clinically important minority involve pathology that requires escalation of care. Deep infiltrating endometriosis may rarely cause bowel obstruction.⁶ Thoracic endometriosis may present with catamenial pneumothorax.⁵ Spontaneous hemoperitoneum from rupture of utero-ovarian vessels, while uncommon, can be life-threatening. Ureteric obstruction from deep disease may be clinically silent until renal injury develops.⁷

Red flags that should prompt broader evaluation or consultation include fever, systemic toxicity, leukocytosis with worsening pain, persistent vomiting with abdominal distension, hypotension, falling hemoglobin, flank pain, hydronephrosis, rising creatinine, or respiratory symptoms temporally linked to menses. These features should shift the differential away from uncomplicated flare and toward complication or alternate diagnosis.

Labs and Imaging: What They Can and Cannot Do in the Emergency Department

Laboratory testing and imaging in the ED are useful primarily to exclude dangerous mimics and identify complications. In uncomplicated endometriosis flares, complete blood count, C-reactive protein, electrolytes, urinalysis, and pelvic ultrasound are often normal. Normal results lower the likelihood of infection, hemorrhage, torsion, and some forms of obstruction when interpreted in the context of a stable clinical presentation. Conversely, abnormal results should push clinicians to reconsider the working diagnosis.³ Leukocytosis, fever, and elevated inflammatory markers suggest infection or abscess. Falling hemoglobin raises concern for hemorrhage. Elevated creatinine or hydronephrosis suggests ureteric obstruction. Electrolyte abnormalities in the setting of vomiting and distension raise concern for bowel obstruction.

Pelvic ultrasound remains first-line imaging when gynecologic emergencies are under consideration and may identify torsion, tubo-ovarian abscess, or endometriomas.³ However, a normal ultrasound does not exclude endometriosis, particularly superficial peritoneal disease or deep infiltrating lesions that require specialized imaging or expert interpretation.⁸ A CT scan is appropriate when appendicitis, bowel obstruction, or other non-gynecologic pathology is suspected. An MRI is superior for characterizing deep infiltrating endometriosis, but this is generally an outpatient investigation and unavailable in the emergency department.³

One of the most common pitfalls is attributing severe pelvic pain to a hemorrhagic cyst when one is seen on ultrasound. Ovarian cysts are commonly incidental or contributory findings in patients with pelvic pain; patients with endometriosis may be repeatedly told that they simply have “hemorrhagic cysts.” Yet physiologic hemorrhagic cysts should resolve within eight to 12 weeks. When a cyst persists on repeat imaging, clinicians should consider endometrioma, an ovarian manifestation of endometriosis and often a marker of deeper disease. This is one of the most actionable interventions available to the emergency physician. When a hemorrhagic cyst is identified, explicitly recommend repeat ultrasound in eight to 12 weeks. That single step may redirect the patient’s diagnostic trajectory and prevent years of mislabeling.

Acute Pain Management in the Emergency Department

Acute pain management in the ED should be pragmatic and multimodal. Inadequate analgesia contributes to repeat visits, patient distrust, and unnecessary suffering. NSAIDs remain first-line therapy for prostaglandin-mediated pain.⁹ When oral administration is limited by nausea or vomiting, parenteral formulations and early antiemetics are helpful. For severe flares, short-acting opioids may be required as a temporary adjunct when non-opioid therapy is insufficient. Opioids should not be the sole strategy, but neither should they be reflexively withheld in a patient with severe distress simply because the condition is recurrent.

Hormonal Therapy as Disease-Modifying Treatment

Hormonal suppression is first-line disease-modifying therapy for suspected or confirmed endometriosis, and in selected cases ED initiation may be reasonable, particularly when symptoms are highly suggestive and timely outpatient follow-up is uncertain.⁹ Progestin-only therapy, such as drospirenone, should not be prescribed in patients with a personal history of breast cancer, severe liver disease, current pregnancy, or undiagnosed abnormal vaginal bleeding.⁴ Combined oral contraceptive pills are contraindicated in patients with migraine with aura, prior venous thromboembolism, hypertension, and smoking at age 35 years or older.⁴ When appropriate, a continuous combined oral contraceptive regimen without a placebo week is a practical strategy to suppress cyclical hormonal fluctuation. If hormonal therapy is initiated, the chart should clearly documentation the indication—suspected endometriosis with severe cyclical pelvic pain—the regimen prescribed, and a defined follow-up plan within weeks. Patients should also be counseled that hormonal therapy controls symptoms rather than cures disease; some will not improve, and recurrence after discontinuation is common.⁴

Communication and Disposition

Communication is a critical component of ED management. Many patients with endometriosis have experienced years of dismissal or misattribution of symptoms. Explicit validation—acknowledging that their pain is severe and real—helps restore trust and encourages engagement with ongoing care. A structured discharge plan should include return precautions, a short-term analgesic strategy, and clear follow-up instructions.¹⁰ Again, repeat ultrasound within eight to 12 weeks should be recommended when hemorrhagic cysts are identified.

Emergency physicians are uniquely positioned to influence the trajectory of endometriosis care. Although the definitive diagnosis is typically established outside the ED, recognition of the clinical pattern, thoughtful risk stratification, effective analgesia, and structured follow-up can meaningfully reduce diagnostic delay and improve patient outcomes. As endometriosis is increasingly recognized as a chronic systemic inflammatory disease rather than merely a gynecologic condition, emergency physicians must incorporate this understanding into routine practice. By reframing recurrent cyclical pelvic pain as a potential manifestation of endometriosis—and responding with deliberate evaluation and management—emergency physicians can play a critical role in interrupting years of missed diagnosis and fragmented care.

A special thanks to Dr. Catherine Varner and Dr. Jennifer McCall, the guest experts on the EM Cases podcast who inspired this column.

DR. HELMAN is an emergency physician at North York General Hospital in Toronto. He is an assistant professor at the University of Toronto, Division of Emergency Medicine, and the education innovation lead at the Schwartz/Reisman Emergency Medicine Institute. He is the founder and host of Emergency Medicine Cases podcast and website (www.emergencymedicinecases.com).

References

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