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Imaging in Pelvic Inflammatory Disease and Tubo-Ovarian Abscess

Practice Essentials

Pelvic inflammatory disease (PID) is a general term indicating infection of the female upper genital tract and the surrounding structures.
It is a common and serious complication of sexually transmitted disease. Acute episodes need appropriate care and treatment; however, it is the long-term sequelae of chronic pelvic pain, infertility, and ectopic pregnancy due to scarring and adhesions that burden the healthcare system in an adverse manner.

It encompasses a broad category of diseases, including endometritis, salpingitis, salpingo-oophoritis, tubo-ovarian abscess (TOA),
and pelvic peritonitis. The afflicted women may be asymptomatic, present with mild nonspecific symptoms, or may have fulminant disease. Prompt diagnosis and treatment of this condition are critical because the complications of PID can be life and fertility threatening.
The varied clinical presentation and imaging findings may make it difficult to diagnose PID, and sometimes it may remain undetected.

Lower abdominal pain and abnormal vaginal discharge are common symptoms. Cervical motion and adnexal tenderness are often elicited on physical examination. In severe cases, patients may present with toxemia and signs of infection such as fever, leukocytosis, elevated erythrocyte sedimentation rate or C-reactive protein level, and laboratory documentation of cervical infection. A palpable adnexal mass may be seen in complicated PID with TOA.

While clinical and laboratory findings are considered sufficient to initiate treatment of PID, this approach may be incorrect, as seen on laparoscopy by Molander et al.
Laparoscopy has been considered the standard for the diagnoses of PID, but it is costly, invasive, and has a reduced sensitivity in mild disease.
Endometrial biopsy has a sensitivity of 92% and a specificity of 87% compared with laparoscopy, as demonstrated in a study by Paavonen et al.
 Imaging is therefore being increasingly used for the diagnosis of PID, particularly in patients with an uncertain diagnosis, in patients with chronic or complex disease, or in patients who have developed complications. Awareness of the various imaging findings is important to be able to suggest and confirm the clinical diagnosis of PID, facilitate timely and appropriate treatment, avert the chronic complications, and decrease morbidity.

Preferred examination

Ultrasonography should be the first diagnostic imaging examination to be performed in cases of suspected PID in which there are ambiguous or unexplained clinical findings or an inability to perform an adequate clinical examination. Ultrasonography is also indicated to evaluate for complications of PID, which may impact operative versus nonoperative management or the decision to hospitalize a patient. This modality is readily available, noninvasive, and can be performed at the patient’s bedside.

Most often, ultrasonography is preferred over CT scanning as the triaging tool in a female child or adolescent with right lower quadrant or pelvic pain, particularly because of concerns about radiation exposure. Transvaginal sonography allows detailed visualization of the uterus and adnexa, including the ovaries and thickened fallopian tubes. Transabdominal sonography is complementary to the endovaginal examination because it provides a more global view of the pelvic contents. Whether transabdominal sonography (bladder filling required) or transvaginal sonography (bladder filling not required) is performed first and whether the complementary examination is needed for a final diagnosis is a matter of individual clinical imaging practice.

MRI serves as an excellent imaging modality in cases in which the ultrasonographic findings are equivocal.
MRI findings in acute PID include cervicitis, endometritis, salpingitis/oophoritis, and inflammation in the pelvic soft tissues. In a study by Tukeva et al, the authors compared findings from MRI with sonograms and found that MRI was more accurate than ultrasonography in the diagnosis of PID.

Occasionally, CT scanning may be used as the initial diagnostic study for the investigation of nonspecific pelvic pain in a female, and PID may be found incidentally. CT scanning is very sensitive for the detection of pelvic pathology; however, it may not be as specific as sonography when an adnexal pathology must be differentiated into a tubal or ovarian one. If the diagnosis of PID is still in question, confirmation with ultrasonography is suggested.

The Centers for Disease Control and Prevention (CDC) has established criteria for the diagnosis of PID.

Ultrasound- or CT-guided aspiration/drainage may be performed for tubo-ovarian or pelvic abscess, with the addition of antibiotic coverage. Preservation of the ovaries is an advantage of image-guided drainage over surgery.

See the PID and tubo-ovarian images below.

Endovaginal sonogram. This image shows anechoic tu

Endovaginal sonogram. This image shows anechoic tubular structures in the adnexal area; the finding is compatible with a hydrosalpinx.

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Endovaginal ultrasound scan. This image shows a re

Endovaginal ultrasound scan. This image shows a relatively enlarged right ovary in a patient who had pain, increased flow, and a small amount of adjacent free fluid. These findings are compatible with oophoritis.

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This sonogram shows a markedly heterogeneous and t

This sonogram shows a markedly heterogeneous and thickened endometrium, a finding that is compatible with endometritis.

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Transabdominal ultrasound scan. This image demonst

Transabdominal ultrasound scan. This image demonstrates an echogenic region within the endometrium with dirty shadowing, a finding that is compatible with air in the endometrium and endometritis. Additionally, bilateral complex masses are present; this finding is compatible with tubo-ovarian masses.

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PID is a complex polymicrobial disease that is due to the ascending spread of pathogens from the cervix or vagina, most commonly Chlamydia trachomatis or Neisseria gonorrhoeae (60-75%) , which then spreads into the endometrium, fallopian tubes, ovaries, and adjacent structures.
Of women with inadequately treated chlamydia or gonorrhea, 10-20% may develop PID.

Other pathogens include Mycoplasma hominis, Haemophilus influenzae, Streptococcus pyogenes, Bacteroides species, and Peptostreptococcus species. Less commonly, direct spread from a nearby infection such as appendicitis or diverticulitis may occur. Hematogenous infection is a rare cause of PID except in cases of tuberculous PID.

Douching is a potential risk factor for PID as it can result in a change of the vaginal flora and introduce bacteria from the vagina into the upper reproductive organs. Usage of intrauterine contraceptive device or gynecologic interventions may also predispose a patient to PID. Direct extension of infection from adjacent viscera and uterine instrumentation are more important risk factors in postmenopausal PID.


Annually, approximately 1 million women develop PID.
PID is most commonly seen in young women and rarely in postmenopausal women. A series reported less than 2% of TOAs in postmenopausal women.
 An estimated 1 in 8 sexually active adolescent girls develop PID before reaching age 20 years. Because PID may be asymptomatic and is frequently undiagnosed, the incidence rate is likely higher. PID contributes to approximately 2.5 million office visits and 125,000-150,000 hospitalizations every year.
 The annual incidence of PID in females aged 15-39 years seems to be 10-13 cases per 1000 women, with a peak incidence of about 20 cases per 1000 women in those aged 20-24 years.

According to WHO estimates, 499 million new cases of curable sexually transmitted infections (ie, syphilis, gonorrhoea, chlamydia, trichomoniasis) occur annually throughout the world in adults aged 15-49 years.
In developing countries, sexually transmitted infections and their complications rank in the top 5 disease categories for which adults seek health care. In addition, antimicrobial resistance, in particular for gonorrhoea, is becoming increasingly widespread. In sub-Saharan Africa, untreated genital infection may account for up to 85% of infertility among women.

The rate of PID in black women is 2-3 times higher than that in white women. This difference is explained by the marked racial disparity in the rates of chlamydia and gonorrhea.

Tubal scarring as a result of PID can cause infertility in 20%, ectopic pregnancy in 9%, and chronic pelvic pain in 18% of women

Complicated PID resulting in tubo-ovarian or pelvic abscess may contribute to patient mortality.


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