Differentials
Ectopic pregnancy
SIGNS / SYMPTOMS
Lower abdominal pain, adnexal tenderness, fever, and other symptoms of acute abdomen (nausea, vomiting, diarrhoea) may be present. May resemble severe case of PID. PID can exist concurrently with ectopic pregnancy.
INVESTIGATIONS
Positive pregnancy test will guide search for ectopic pregnancy: hCG hormone level is high in serum and urine.
Ultrasound reveals an empty uterus and may show a mass in the fallopian tubes.
Acute appendicitis
SIGNS / SYMPTOMS
Nausea and vomiting occurs in most patients with acute appendicitis. Cervical motion tenderness will occur in about 25% of women with appendicitis while this sign is usually present in all patients with PID.
INVESTIGATIONS
Abdominal ultrasound: aperistaltic or non-compressible structure with outer diameter >6 mm; sensitivity for diagnosis of acute appendicitis is 75% to 90%.[33]
Abdominal and pelvic CT scan: abnormal appendix (diameter >6 mm) identified or calcified appendicolith seen in association with periappendiceal inflammation; sensitivity for diagnosis of acute appendicitis is 87% to 98%.[33]
Laparoscopy confirms diagnosis.
Ovarian cyst complications (ruptured ovarian cyst, ovarian cyst torsion, haemorrhagic ovarian cyst)
SIGNS / SYMPTOMS
Ruptured ovarian cyst: rupture usually spontaneous, can follow history of trauma; mild chronic lower abdominal discomfort may suddenly intensify. On examination, signs of peritonism (guarding, rebound tenderness, rigid abdomen) may be present in lower abdomen and pelvis; size of the adnexal mass may be unremarkable due to collapsed cyst.
Ovarian cyst torsion: typical presentation is with sudden, acute, unilateral, lower quadrant abdominal pain, severe and colicky in nature; two thirds of patients have nausea and vomiting. Low-grade fever usually correlates with necrosis; tender adnexal mass palpated in 90%; localised peritoneal irritation.
Haemorrhagic ovarian cyst: presents with localised abdominal pain, nausea, and vomiting. Clinical examination may be unremarkable. Rarely, and depending on size of cyst, hypovolaemic shock may be present; abdominal tenderness and peritonism; pelvic mass may be palpated.
INVESTIGATIONS
Pelvic ultrasound confirms diagnosis.
Endometriosis
SIGNS / SYMPTOMS
Adnexal enlargement, cervical stenosis, or lateral displacement of uterus; cyclic pain that is exacerbated by onset of menses and during the luteal phase; or dyspareunia. Cyclic pain is not a feature of PID.
INVESTIGATIONS
Transvaginal ultrasound may show ovarian endometrioma or evidence of deep pelvic endometriosis such as uterosacral ligament involvement.
Laparoscopy confirms diagnosis by direct visualisation of peritoneal implants with biopsy-confirmed endometrial glands or stroma outside of uterine cavity.
Non-PID causes of vaginal discharge
SIGNS / SYMPTOMS
Vulvovaginal symptoms: discharge, itching, burning, dyspareunia. Vulvovaginal symptoms may or may not present in PID because upper tract disease may exist in the absence of symptoms of vaginitis.
INVESTIGATIONS
Vaginal discharge tested by wet mount or genetic probe or urethral swab identifies causative organism.
Myofascial pain syndrome
SIGNS / SYMPTOMS
Tenderness confined to one anatomical region. Region may be lower abdomen and pelvis. Does not have associated PID features of fever, elevated white blood cell count, elevated erythrocyte sedimentation rate, vaginal discharge and/or positive Neisseria gonorrhoeae and Chlamydia trachomatis cultures, and adnexal or cervical tenderness.
INVESTIGATIONS
Palpation of trigger points produces reproducible pain.
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