Pelvic inflammatory disease

Pelvic inflammatory disease (PID) is a broad term that encompasses a spectrum of infection and inflammation of the upper female genital tract, resulting in a range of abnormalities. 

Epidemiology

The highest incidence is seen among sexually-active women in their teens, with 75% cases being under 25 years of age.  In the United States, approximately 1 million females are thought to be afflicted with pelvic inflammatory disease per year, and nearly 275,000 of them are believed to be hospitalised ⁷.

Clinical presentation

More common presentations include acute pelvic pain (of variable intensity), cervical motion tenderness, vaginal discharge, fever, dyspareunia, and leukocytosis. Right upper quadrant pain from perihepatitis in Fitz-Hugh-Curtis syndrome is possible.

Pathology

PID is defined as an acute clinical syndrome associated with ascending spread of micro-organisms, unrelated to pregnancy or surgery. The infection generally ascends from the vagina or cervix to the endometrium (endometritis), then to the fallopian tubes (salpingitis), and then to and/or contiguous structures (tubo-ovarian abscess). 

It can result from a number of causative organisms:

• common
  • Chlamydia trachomatis: pelvic chlamydial infection
  • Neisseria gonorrhoeae: pelvic gonococcal infection
  • polymicrobial infection: can account for ~35% of cases ³
• less common
  • Mycobacterium tuberculosis: pelvic tuberculous infection
  • Actinomyces spp.: pelvic actinomyces infection

PID is usually bilateral, except when it is caused by the direct extension of an adjacent inflammatory process such as appendiceal, diverticular, or post-surgical abscesses.

Radiographic features

Imaging features are often non-specific but are disproportionate to what may be apparent from symptoms. If imaged early (e.g. during the cervicitis stage), there may be no finding. If imaged very late, there may be an adnexal mass-like region with surrounding inflammatory change, and the fallopian tube and ovary may not be able to be distinguished.

Other associated findings include ⁷:

• soft-tissue stranding and infiltration of pelvic floor fascial planes
• thickening of uterosacral ligaments

Ultrasound

Ultrasound often only demonstrates ascitic fluid in the peritoneal cavity or non-specific thickening and increased vascularity of the endometrium ⁸.

In the most severe cases, ultrasound may show adnexal masses with a heterogeneous echo-pattern.

Some sonographic signs associated with tubal inflammation include:

• thickened/dilated fallopian tubes
  • incomplete septa in the tube
  • increased vascularity around the tube
  • echogenic fluid in the tube (pyosalpinx)

• cogwheel sign
• beads on a string sign

CT

• thickening of the uterosacral ligaments
• complex free fluid in the pouch of Douglas (cul-de-sac)
• pelvic fat stranding or haziness
• indistinct uterine border
• fallopian tube thickening of >5 mm with enhancing wall
• reactive lymphadenopathy
  • lymph nodes in the para-aortic and paracaval regions often become prominent due to infection draining in to lymphatics along the course of the gonadal veins

MRI

May show an ill-defined adnexal mass containing fluid with various signal intensities:

• T1+C (Gd): wall and surrounding tissues may enhance

Treatment and prognosis

In the absence of complications, pelvic inflammatory disease is often treated conservatively with education, antibiotics, and partner tracing.

Complications

• tubo-ovarian abscess
• pyosalpinx
• infertility due to tubal adhesions
• peritonitis
• ovarian vein thrombosis
• peritoneal adhesion formation with resultantcausing bowel obstruction
• Fitz-Hugh-Curtis syndrome

Differential diagnosis

• fallopian tube carcinoma
  • rare
  • consider in a patient without risk factors for PID and/or a patient in whom a course of antibiotics did not resolve the PID