Pelvic inflammatory disease — lower abdominal pain in a 23-year-old

Diagnosis and assessment. This is pelvic inflammatory disease. She meets the minimum CDC clinical criteria (cervical motion tenderness, uterine tenderness, and adnexal tenderness on bimanual examination, with no other cause identified), and the specificity-improving features are all present: a fever over 38.3 degrees, a mucopurulent cervical discharge, and the sexual risk of a new partner with no barrier contraception. The beta-hCG is negative, which excludes ectopic pregnancy — the diagnosis that must be excluded before any other step. She is haemodynamically stable, has no peritonism, and has no clinical features of a tubo-ovarian abscess, so she is a candidate for outpatient management. The differential held in parallel is appendicitis (no migrating right-lower-quadrant pain, vomiting or anorexia).^[1]

Investigations. The beta-hCG (already done) is mandatory in every woman of reproductive age with lower abdominal pain. A nucleic-acid amplification test for Neisseria gonorrhoeae and Chlamydia trachomatis is taken (endocervical, self-taken vaginal swab, or first-void urine), and testing for Mycoplasma genitalium is added where available. A full sexually-transmitted-infection screen adds HIV and syphilis serology, with hepatitis B and C as appropriate. Urinalysis excludes a urinary tract infection. Full blood count, CRP and ESR are sent (the raised inflammatory markers sharpen the diagnostic specificity). Saline wet-mount microscopy of vaginal fluid, where available, shows the abundant white cells of upper-tract inflammation. A pelvic ultrasound is reasonable but must not delay treatment.^[1]

Management — the antibiotic regimen. Treatment begins at moment diagnosis is made and is not delayed for the NAAT result. As an outpatient she receives the CDC 2021 regimen: ceftriaxone 500 mg intramuscularly as a single dose (1 g if she weighs over 150 kg), plus doxycycline 100 mg orally twice daily for 14 days, plus metronidazole 500 mg orally twice daily for 14 days. Metronidazole is mandatory, not optional, because PID is polymicrobial and the anaerobic and bacterial-vaginosis organisms must be covered. She receives analgesia and is advised to abstain from intercourse until she and her partners have completed treatment.^[1]

Disposition — outpatient, because no admission criterion is met. She is not pregnant, has no tubo-ovarian abscess, has no peritonitis or sepsis, can tolerate oral therapy, will return for review, and appendicitis and the other surgical mimics have been reasonably excluded. She is therefore discharged on the 14-day outpatient regimen. (Admission criteria to state: pregnancy; a surgical emergency that cannot be excluded; severe illness with nausea, vomiting, high fever, peritonitis or sepsis; a tubo-ovarian abscess; failure of oral therapy; inability to tolerate or follow the oral regimen; or follow-up that cannot be assured.)^[1]

Partner management. All sexual partners of the preceding 60 days are tested and treated, and expedited partner therapy is offered where the jurisdiction permits. This is the step that prevents reinfection and recurrent PID, which are the drivers of tubal infertility. Mandatory notification of gonorrhoea and chlamydia applies in most Australian states and in New Zealand.^[1]

Follow-up and the safety-net. A clinical review is arranged at 48 to 72 hours. No improvement at that point is defined as treatment failure and mandates admission for parenteral antibiotics, re-imaging for a tubo-ovarian abscess, and reconsideration of appendicitis, ectopic pregnancy and torsion. A repeat NAAT is arranged at three months because the reinfection rate is high, and the Mycoplasma genitalium result is acted on per its macrolide-resistance profile. Finally, she is counselled on the long-term reproductive sequelae — tubal infertility, ectopic pregnancy and chronic pelvic pain — and on the contraception that reduces recurrence.^[1]