Pelvic inflammatory disease (PID) is an infectious and inflammatory disorder of the upper female genital tract, including the uterus, fallopian tubes, and adjacent pelvic structures. Infection and inflammation may spread to the abdomen, including perihepatic structures (Fitz-Hugh−Curtis syndrome). The classic high-risk patient is a menstruating woman younger than 25 years who has multiple sex partners, does not use contraception, and lives in an area with a high prevalence of sexually transmitted disease (STD).
PID is initiated by infection that ascends from the vagina and cervix into the upper genital tract. Chlamydia trachomatis is the predominant sexually transmitted organism associated with PID. Of all acute PID cases, less than 50% test positive for the sexually transmitted organisms such as Chlamydia trachomatis and Neisseria gonorrhea. 
) Other organisms implicated in the pathogenesis of PID include, Gardnerella vaginalis (which causes bacterial vaginosis (BV), Haemophilus influenzae, and anaerobes such as Peptococcus and Bacteroides species. Laparoscopic studies have shown that in 30-40% of cases, PID is polymicrobial. (See Etiology.)
The diagnosis of acute PID is primarily based on historical and clinical findings. Clinical manifestations of PID vary widely. Many patients exhibit few or no symptoms, whereas others have acute, serious illness. The most common presenting complaint is lower abdominal pain. Many women report an abnormal vaginal discharge. (See Presentation.)
The differential diagnosis includes appendicitis, cervicitis, urinary tract infection, endometriosis, ovarian torsion and adnexal tumors. Ectopic pregnancy can be mistaken for PID; indeed, PID is the most common incorrect diagnosis in cases of ectopic pregnancy. Consequently, a pregnancy test is mandatory in the workup of women of childbearing age who have lower abdominal pain. (See DDx.)
PID may produce tubo-ovarian abscess (TOA) and may progress to peritonitis and Fitz-Hugh−Curtis syndrome (perihepatitis; see the image below).  Note that a rare but life-threatening complication of acute rupture of a TOA may result in diffuse peritonitis and necessitate urgent abdominal surgery. [2, 3, 4, 5] See Imaging in Pelvic Inflammatory Disease and Tubo-Ovarian Abscess for more information.
Laparoscopy is the current criterion standard for the diagnosis of PID. No single laboratory test is highly specific or sensitive for the disease, but studies that can be used to support the diagnosis include the erythrocyte sedimentation rate (ESR), the C-reactive protein (CRP) level, and chlamydial and gonococcal DNA probes and cultures, endometrial biopsy, imaging studies (eg, ultrasonography, computed tomography [CT], and magnetic resonance imaging [MRI]) may be helpful in unclear cases. (See Workup.)
Most patients with PID are treated in an outpatient setting. In selected cases, however, physicians should consider hospitalization. (See Treatment.)
Empirical antibiotic treatment is recommended for patients with otherwise unexplained uterine or adnexal tenderness and cervical motion tenderness, according to guidelines from the Centers for Disease Control and Prevention (CDC). Antibiotic regimens for PID must be effective against C trachomatis and N gonorrhoeae, as well as against gram-negative facultative organisms, anaerobes, and streptococci.
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