PID occurs due to ascending infection from the cervix extending through the endometrial cavity into fallopian tubes and adnexa. The initial infection is usually caused by Chlyamydia trachomatis or Neisseria gonorrhoeae, with subsequent colonization by anaerobes, gram-negative bacteria, and streptococci. Predisposing factors include history of sexually transmitted disease or PID, multiple sexual partners, and presence of intrauterine device (IUD). TOA can be unilateral or bilateral, independent of IUD use.

Presentation of TOA is nonspecific and similar to PID, including abdominal or pelvic pain (>90%), fever and leukocytosis (60-80%), vaginal discharge, vaginal bleeding, nausea, cervical motion tenderness, and palpable pelvic mass. Some patients with TOA may be asymptomatic or have mild symptoms. Absence of fever or leukocytosis does not exclude the diagnosis of TOA. Seventy percent of women with PID are younger than 25 years. A white blood cell (WBC) and β-human chorionic gonadotropin (hCG) should be obtained in all patients suspected of having TOA.

Differential diagnosis includes hydro- or pyosalpinx, ectopic pregnancy, endometriosis, ovarian neoplasm/cyst, ovarian torsion, appendicitis, and diverticulitis.

Diagnosis of PID should be made on the basis of symptoms, clinical examination, and laboratory tests, not imaging. Imaging is indicated in patients with suspected PID who have a palpable mass, are severely ill and need inpatient therapy, are failing to respond to antibiotic therapy, or whose discomfort prevents an adequate pelvic examination. The primary goal of imaging is to differentiate between TOA and uncomplicated PID, which requires establishing the presence or absence of an inflammatory adnexal mass. Ultrasonography is the imaging test of choice for evaluation of TOA with up to 93% sensitivity and up to 98% specificity.

Transabdominal and endovaginal ultrasonography should be performed. Endovaginal examination has a greater sensitivity and specificity than transabdominal examination alone and must be performed unless the patient’s symptoms are unbearable.