Differential Diagnosis for a 27-year-old Female with Severe Pelvic Pain and History of Early Pregnancy

The patient presents with severe pelvic pain radiating down her left leg, a history of early pregnancy, and known ovarian cysts. Given her symptoms and history, the following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Ovarian Torsion: This is a highly plausible diagnosis given the patient's history of ovarian cysts and the sudden onset of severe pelvic pain radiating down one leg. Ovarian torsion is a gynecological emergency that requires prompt diagnosis and treatment.

• Other Likely Diagnoses

  • Ectopic Pregnancy: Although the patient has been followed by OB and had an ultrasound showing a gestational sac, the possibility of an ectopic pregnancy, especially if the initial ultrasound was done early in the pregnancy, cannot be entirely ruled out without further evaluation.
  • Ruptured Ovarian Cyst: The patient's history of ovarian cysts and the acute onset of pain suggest that a ruptured cyst could be a possible cause of her symptoms.
  • Pelvic Inflammatory Disease (PID): While less likely given the absence of vaginal bleeding or discharge, PID could still be a consideration, especially if there's a history of sexually transmitted infections or previous pelvic infections.

• Do Not Miss Diagnoses

  • Appendicitis: Although the pain is primarily pelvic and radiates down the leg, appendicitis can sometimes present with atypical pain patterns, especially in pregnant women, where the appendix may be displaced due to the enlarging uterus.
  • Pulmonary Embolism: Pregnancy increases the risk of thromboembolic events. Severe pain and the potential for deep vein thrombosis (DVT) leading to pulmonary embolism make this a critical diagnosis not to miss, despite its lower likelihood based on the presentation.
  • Ruptured Ectopic Pregnancy: Even if less likely due to previous OB follow-up, a ruptured ectopic pregnancy is a life-threatening condition that must be considered and ruled out promptly.

• Rare Diagnoses

  • Degenerating Uterine Leiomyoma (Fibroid): While fibroids are common, they rarely cause acute severe pain unless they undergo degeneration, which could be a consideration in this pregnant patient.
  • Adnexal Mass (e.g., Dermoid Cyst): Other types of adnexal masses could cause pain, either due to torsion or rupture, but are less common than ovarian cysts or torsion.

The workup for this patient should include:

• Immediate ultrasound to evaluate the ovaries, adnexa, and uterus, including a transvaginal approach if necessary.
• Pregnancy test (beta-hCG) to assess for any changes that might suggest an ectopic pregnancy.
• Complete blood count (CBC) and blood type, in case surgical intervention is needed.
• Consider CT scan or MRI if the diagnosis remains unclear after ultrasound, though this should be done with caution in pregnancy.
• Clinical assessment for signs of infection, such as fever or abnormal discharge.
• D-dimer or lower extremity Doppler if there's suspicion of DVT or pulmonary embolism, though these tests have limitations in pregnancy.

Given the patient's symptoms and history, prompt evaluation and diagnosis are crucial to guide appropriate management and prevent potential complications.