Differential Diagnosis

The patient presents with nausea, vomiting, pelvic pain, and a recent history of intrauterine device (IUD) placement. The symptoms and findings suggest several possible diagnoses, categorized as follows:

• Single Most Likely Diagnosis

  • Pelvic Inflammatory Disease (PID): The patient's symptoms of pelvic pain, nausea, vomiting, fever (38.3°C), and cervical motion tenderness, along with the recent IUD placement, make PID a highly likely diagnosis. The presence of complex, multiloculated masses on the left adnexa on ultrasound further supports this diagnosis, as it could indicate a tubo-ovarian abscess, a complication of PID.

• Other Likely Diagnoses

  • Ectopic Pregnancy: Although less likely given the patient's IUD, ectopic pregnancy should be considered, especially with pelvic pain and a complex adnexal mass. However, the patient's symptoms have been present for four days, and the IUD reduces the likelihood of pregnancy.
  • Ovarian Cyst or Torsion: The ultrasound findings could also suggest an ovarian cyst, and the severe pain, especially with walking, might indicate torsion. However, the fever and cervical motion tenderness are less typical for these conditions.
  • Infection or Perforation Related to IUD: Given the recent IUD placement, an infection or perforation related to the device is possible, though less common.

• Do Not Miss Diagnoses

  • Ruptured Ectopic Pregnancy: Although the patient has an IUD, a ruptured ectopic pregnancy is a life-threatening condition that must be ruled out, especially with severe pelvic pain and signs of instability.
  • Appendicitis: While the pain is more typically on the right side, appendicitis can present atypically, especially in women, and must be considered due to its potential for severe complications if missed.
  • Ovarian Torsion: This is another condition that, while possibly less likely, requires prompt surgical intervention to preserve ovarian function.

• Rare Diagnoses

  • Malignancy: Although rare in this age group, ovarian malignancy could present with complex masses and pelvic pain. The acute presentation and fever make this less likely, but it should be considered in the differential diagnosis.
  • Endometriosis: While endometriosis can cause chronic pelvic pain and could potentially cause a mass if an endometrioma is present, the acute presentation with fever and the specific ultrasound findings make this a less likely diagnosis in this scenario.