Pelvic Inflammatory Disease

• Ascending infection and bacterial colonization: The lower genital tract contains commensal flora including lactobacilli that normally maintain vaginal pH between 3.8-4.5, creating an acidic environment unfavorable to pathogenic bacteria. Sexually transmitted pathogens (Neisseria gonorrhoeae and Chlamydia trachomatis) express specialized adhesins (pilin for N. gonorrhoeae, major outer membrane protein [MOMP] for C. trachomatis) that facilitate attachment to columnar epithelium of the endocervix. These organisms possess lipopolysaccharide (LPS) in their outer membranes that triggers toll-like receptor (TLR) signaling, particularly TLR4, activating innate immunity. During menses, when the endocervical mucus plug is absent and the endometrial cavity is open, bacteria ascend through the uterine cavity into the fallopian tubes. Non-gonococcal, non-chlamydial organisms—including Mycoplasma genitalium, Gardnerella vaginalis, anaerobes (Prevotella, Peptostreptococcus), and facultative anaerobes (Streptococcus agalactiae, Escherichia coli)—also contribute to PID, particularly in cases of bacterial vaginosis preceding infection.

• Mucosal invasion and inflammatory cascade: Once pathogenic organisms reach the fallopian tubes, they invade the mucosal epithelium, disrupting the normal ciliary architecture and tight junctions. Neisseria gonorrhoeae produces gonococcal opacity proteins (Opa) that interact with carcinoembryonic antigen-related cell adhesion molecule (CEACAM) receptors on epithelial cells, promoting transcytosis and paracellular invasion. Chlamydia trachomatis replicates within endocytic inclusions, and the bacterium produces lipoproteins and peptidoglycans that activate pattern recognition receptors. Bacterial endotoxin (LPS) and exotoxins stimulate resident macrophages and dendritic cells to produce tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8), establishing a pro-inflammatory milieu. IL-8 serves as a potent chemokine, recruiting polymorphonuclear leukocytes (PMNs) that aggregate within the tubal lumen and endometrium. The recruitment of innate immune cells and subsequent adaptive immune response (Th1 and Th17 cell differentiation, driven by *Chlamydia*-specific antigens) paradoxically contributes to tissue damage through excessive inflammation. Matrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9, are upregulated and degrade collagen and proteoglycans in the extracellular matrix, promoting mucosal ulceration and increased epithelial permeability.

• Tubal damage and chronic sequelae: Repeated or persistent infection initiates pathologic remodeling of the fallopian tube. The acute inflammatory infiltrate eventually resolves, but fibroblasts proliferate and lay down collagen, leading to stricture formation and partial or complete luminal occlusion. The ciliated columnar epithelium undergoes metaplasia to non-ciliated cuboidal epithelium, impairing oviductal transport of gametes. Chronic inflammatory infiltrates containing T lymphocytes and plasma cells persist in the tube walls. These structural alterations underlie the high rates of infertility (20-40% after one episode, with risk proportional to episode number and severity) and ectopic pregnancy risk (relative risk 6-10 times baseline), as partially occluded tubes allow sperm passage but impede embryo transport. Adhesion formation between tubes, ovaries, and surrounding peritoneum further compromises fertility and predisposes to recurrent PID.

• Host factors modulating disease severity: Estrogen and progesterone modulate immune responses and mucosal integrity. Estrogen enhances TLR expression and promotes Th1 responses, whereas progesterone has immunosuppressive effects. The menstrual cycle phase influences susceptibility and disease presentation; infection is more likely during menses when the endometrium is denuded and estrogen levels are declining. Genetic polymorphisms in pattern recognition receptors (e.g., TLR4) and cytokine genes (e.g., TNF-α promoter variants) influence individual susceptibility to severe disease. Smoking impairs mucociliary clearance and reduces local IL-12 production, increasing both acquisition risk and severity. The presence of bacterial vaginosis fundamentally alters the vaginal microbiota from *Lactobacillus*-dominated to anaerobic-dominated flora, with Gardnerella, Prevotella, and Ureaplasma, increasing both PID risk (odds ratio 2-3) and severity.

• Sexually transmitted infections (STIs)—primary pathogens: Neisseria gonorrhoeae and Chlamydia trachomatis are responsible for approximately 60% of culture-documented PID cases in Western cohorts. N. gonorrhoeae causes acute, symptomatic PID in roughly 10-15% of infected women if untreated; symptoms typically appear within 1-2 weeks of cervical infection. C. trachomatis causes PID in approximately 5-10% of untreated cervicitis and often produces subclinical upper tract infection with delayed or minimal symptoms, potentially explaining the delayed diagnosis (mean 8-10 days from symptom onset) that increases complications. Serovars D through L (non-invasive serovars) cause genital infection, while L1-L3 (invasive serovars causing lymphogranuloma venereum) less commonly cause PID but present with severe systemic symptoms. Mycoplasma genitalium, an emerging pathogen identified in 15-30% of PID cases in some cohorts, is associated with high rates of tubal factor infertility and persistent/recurrent infection.

• Bacterial vaginosis and anaerobic bacteria: Bacterial vaginosis (BV) is present in 40-50% of women with PID. The altered vaginal microbiota in BV (characterized by reduction of protective Lactobacillus species and overgrowth of anaerobes including Prevotella, Gardnerella vaginalis, Mobiluncus, and Ureaplasma parvum) facilitates ascending polymicrobial infection. Gardnerella vaginalis produces biofilms that impair local immunity and promote persistence. Anaerobic organisms produce virulence factors including lipopolysaccharides that enhance the inflammatory response and increase tissue damage. Women with BV have 2-3 times higher risk of developing PID, and BV-associated PID is more likely to involve polymicrobial infection and tubo-ovarian abscess.

• Other bacterial pathogens: Streptococcus agalactiae (Group B Streptococcus), Escherichia coli, and other gram-negative rods are commonly isolated from PID, particularly in cases with intra-abdominal pathology (appendicitis, diverticulitis) or in older women. These organisms frequently cause TOA with associated bacteremia. Mycobacterium tuberculosis causes chronic PID in endemic regions, presenting insidiously with chronic pelvic pain, infertility, and tubal strictures on hysterosalpingography (classic "beaded" appearance).

• Risk factors for STI acquisition and ascending infection: Multiple sexual partners, inconsistent condom use, younger age (highest incidence aged 15-24), new sexual partner within 3 months, and history of prior STI are established sexual risk factors. Barrier contraceptive use (condoms) is protective (reduces PID risk by 50-90%), whereas hormonal contraceptive use (oral contraceptives, hormonal IUD) is paradoxically associated with increased PID risk through multiple mechanisms: estrogen-mediated effects on cervical mucus viscosity, altered innate immune responses (reduced neutrophil migration), and prolonged infection duration. Intrauterine device (IUD) use increases PID risk 2-3 fold, particularly in the first 3 weeks after insertion; however, modern copper IUDs are associated with lower risk than older multiload designs, and the absolute risk remains low (1-2 per 1000 woman-years), with risk highest in nulliparous women. IUD-related PID typically occurs when STI was present at insertion or acquired shortly thereafter; routine screening before insertion substantially reduces this risk.

• Other risk factors: Sexually active women with untreated cervicitis or urethritis have substantially elevated PID risk. Douching, which disrupts normal flora and facilitates bacterial ascension, increases PID risk 1.7-4.6 fold. Smoking impairs mucociliary clearance and alters immune responses. Immunosuppression (HIV with CD4 <200, other immunocompromising conditions) increases severity and risk of TOA. Post-abortal PID occurs in 5-15% of women undergoing medical or surgical abortion, particularly if cervical STI screening was not performed preoperatively. Post-partum endometritis can extend to cause PID, especially if delivery was complicated by retained products of conception or chorioamnionitis. Disruption of the endocervical barrier by procedures including dilation and curettage (D&C), insertion of IUDs, hysterosalpingography, or dilation and evacuation facilitates ascension of organisms already colonizing the lower genital tract within days to weeks of the procedure.

• Pelvic pain and lower abdominal pain—cardinal symptom: Pain is the most consistent presenting complaint, present in >90% of symptomatic cases. The pain is typically bilateral, located in the lower abdomen and pelvis, and often described as dull, aching, or cramping. Visceral innervation of the uterus, fallopian tubes, and ovaries via sympathetic fibers (T10-L1) and parasympathetic fibers (pelvic splanchnic nerves) produces midline or periumbilical pain, while parietal peritoneal involvement causes somatic pain (sharp, well-localized, exacerbated by movement). Pain may be constant or intermittent and varies in intensity from mild discomfort requiring no intervention to severe pain necessitating opioid analgesia. The pain typically begins during or shortly after menstruation, when endocervical accessibility is maximal and endometrial immunity is reduced.

• Abnormal vaginal discharge and cervicitis: Mucopurulent cervical discharge (ranging from scant to copious, often yellowish or greenish) results from neutrophilic infiltration of the endocervix and inflammation of the cervical columnar epithelium. Dysuria (painful urination) occurs in 30-50% of cases due to urethritis or cystitis from ascending infection or bladder peritonitis. Some women note vaginal bleeding or postcoital bleeding due to cervicitis and endometrial inflammation.

• Systemic symptoms and fever: Fever (temperature >38°C) is present in approximately 50% of acute PID cases; higher fever (>39°C) raises suspicion for TOA or peritonitis. Patients may report chills, night sweats, malaise, and fatigue. Nausea and vomiting occur in 10-25% of cases, particularly when peritoneal inflammation is pronounced. The presence or absence of fever does not reliably distinguish uncomplicated PID from complicated disease with TOA, as some women with TOA remain afebrile.

• Physical examination findings: Cervical motion tenderness (CMT) and uterine tenderness represent key diagnostic findings. CMT is elicited by gentle lateral motion of the cervix with a finger inserted into the vagina during speculum examination; pain with this maneuver indicates peritoneal irritation. During bimanual examination, the uterus is typically tender to palpation and may feel enlarged and boggy from edema. Adnexal tenderness is present in 50-70% of cases; unilateral adnexal mass or fullness may indicate tubo-ovarian complex or abscess. Rebound tenderness of the lower abdomen indicates peritoneal involvement. Palpable adnexal masses may be detected in up to 30% of acute PID cases and suggest possible TOA or pyosalpinx.

• Clinical variants and atypical presentations:
• Chlamydia-associated PID often presents insidiously with mild to moderate symptoms and subtle physical findings, potentially leading to delayed diagnosis; ~50% of Chlamydia PID cases are considered "silent" with minimal symptoms.
• Gonococcal PID typically presents acutely with severe pain and prominent systemic symptoms.
• Perihepatitis (Fitz-Hugh-Curtis syndrome) represents dissemination of infection to the liver capsule via transperitoneal spread or lymphatic drainage, causing severe right upper quadrant pain and pleuritic features; historically associated with N. gonorrhoeae but now more commonly seen with C. trachomatis.
• Sepsis with tubo-ovarian abscess manifests as high fever, severe abdominal pain, marked peritoneal signs, leukocytosis with left shift, and hemodynamic instability.
• Subclinical endometritis may be entirely asymptomatic or manifest with only abnormal uterine bleeding.

• Clinical diagnostic criteria (CDC 2015): PID should be suspected in women with pelvic pain and one or more of the following minimum clinical criteria: (1) cervical motion tenderness, OR (2) uterine tenderness, OR (3) adnexal tenderness. No other cause for illness can be identified—this is a critical exclusion criterion. Diagnosis is presumed clinically, and empiric treatment is initiated without awaiting laboratory confirmation, as delays increase morbidity. Additional clinical findings supporting diagnosis include fever (>38.3°C), abnormal cervical mucopurulent discharge or cervical friability, presence of WBCs on saline wet mount of vaginal fluid, elevated erythrocyte sedimentation rate (ESR), elevated C-reactive protein (CRP), or positive test for gonorrhea or Chlamydia.

• Microbiologic testing: Cervical specimens should be obtained for nucleic acid amplification testing (NAAT) to detect Neisseria gonorrhoeae and Chlamydia trachomatis. NAAT is the gold standard with >95% sensitivity and >99% specificity for both organisms and is superior to culture. Gram stain of cervical secretions showing >30 WBCs per high-power field or gram-negative diplococci within neutrophils suggests gonorrhea but is insensitive (30-60%). Vaginal wet mount microscopy should be performed in all women with pelvic pain to evaluate for trichomonads (associated with PID in ~5% of cases) and to assess for clue cells and reduced lactobacilli (suggesting bacterial vaginosis, which predisposes to PID). Cultures of endocervical secretions, while less sensitive than

Immediate steps before antibiotics

• Urine/serum hCG: mandatory in every case — ectopic pregnancy is the can't-miss mimic, and pregnancy changes both disposition (hospitalize) and drug selection.
• Hemodynamic assessment: hypotension, marked peritonitis, or rigid abdomen suggests ruptured tubo-ovarian abscess (TOA) — IV fluids, blood cultures, broad-spectrum IV antibiotics, and immediate surgical consultation.

• Third-generation cephalosporin: ceftriaxone 500 mg IM × 1 (1 g if ≥150 kg) — covers N. gonorrhoeae including penicillinase producers.
• Tetracycline: doxycycline 100 mg PO BID × 14 days — intracellular coverage for C. trachomatis; note that doxycycline does not reliably eradicate M. genitalium, and moxifloxacin should be considered if M. genitalium is identified or PID fails to respond.
• Nitroimidazole: metronidazole 500 mg PO BID × 14 days — now recommended with the outpatient regimen given the anaerobic/bacterial-vaginosis contribution.

• Cephamycin plus doxycycline: cefotetan 2 g IV q12h or cefoxitin 2 g IV q6h plus doxycycline 100 mg PO/IV q12h; alternatively ceftriaxone 1 g IV q24h plus doxycycline plus metronidazole 500 mg PO/IV q12h. Oral doxycycline is preferred over IV because infusion is painful.
• Clindamycin 900 mg IV q8h plus gentamicin (loading dose followed by maintenance dosing, or once-daily dosing): alternative, particularly useful in severe cephalosporin allergy and for TOA.

Procedural and definitive management

• TOA: antibiotics alone often suffice for smaller abscesses; image-guided percutaneous or transvaginal drainage for large abscesses or failure to defervesce in 48–72 hours.
• Ruptured TOA: surgical emergency — laparotomy/laparoscopy with drainage, occasionally salpingo-oophorectomy.

Contraindicated or obsolete

• Fluoroquinolones are no longer recommended for gonorrhea in the US because of widespread resistance; they are reserved for documented cephalosporin allergy with susceptibility data.
• Doxycycline and fluoroquinolones in pregnancy: pregnant patients are admitted for parenteral therapy with pregnancy-compatible agents.
• Reflex IUD removal is not required; treat and reassess, removing only if no clinical improvement.

Emergencies

• Ruptured tubo-ovarian abscess: purulent contents spill into the peritoneum, producing diffuse peritonitis and gram-negative/anaerobic septic shock. Signaled by sudden worsening of pain, rigid abdomen with rebound, tachycardia, and hypotension — immediate operative drainage plus broad-spectrum antibiotics.
• Sepsis/bacteremia: more common with E. coli, group B Streptococcus, and anaerobes; heralded by fever with hypotension, leukocytosis with left shift, and rising lactate.

Infectious extension

• Tubo-ovarian abscess (unruptured): walled-off collection of pus involving tube and ovary; suggested by adnexal mass with persistent fever despite 48–72 hours of appropriate antibiotics; confirmed on transvaginal ultrasound as a complex multiloculated adnexal collection.
• Pyosalpinx (acute): obstruction of the fimbriated end traps purulent exudate within a thick-walled tube with edematous, thickened endosalpingeal folds — the classic "cogwheel sign" on transverse sonographic imaging.
• Hydrosalpinx (chronic): after the acute inflammation resolves, the occluded tube distends with serous fluid, giving a thin-walled, dilated tubular structure with incomplete septa — the "beads-on-a-string" appearance.
• **Perihepatitis (Fitz-Hugh-Curtis syndrome)**: transperitoneal spread to the liver capsule; right upper quadrant pleuritic pain with normal or near-normal transaminases, and "violin-string" adhesions at laparoscopy.

Late reproductive sequelae (mechanism = scarring)

• Tubal factor infertility: ciliary destruction and collagen deposition occlude the lumen; risk rises with each episode.
• Ectopic pregnancy: partially patent, dysmotile tubes allow sperm ascent but impede embryo transport — presents as amenorrhea with pain and positive hCG.
• Chronic pelvic pain and recurrent PID: dense adhesions and impaired mucosal defense; adhesive disease can rarely cause small-bowel obstruction.

Treatment-related

• Doxycycline: pill esophagitis, photosensitivity; contraindicated in pregnancy (fetal tooth/bone deposition).
• Metronidazole: metallic taste and a disulfiram-like reaction with alcohol.
• Gentamicin: nephrotoxicity (rising creatinine) and irreversible ototoxicity/vestibulotoxicity.
• Clindamycin: Clostridioides difficile colitis — new watery diarrhea on therapy.
• Ceftriaxone: hypersensitivity; biliary sludging with prolonged use.

• **The *chandelier sign***: extreme cervical motion tenderness on bimanual exam ("the patient jumps to the chandelier") is the classic buzzword for PID; uterine or adnexal tenderness satisfies the CDC minimum criteria just as well.
• Single best next step in a young woman with pelvic pain: a pregnancy test, always, before committing to a PID diagnosis — ectopic pregnancy is the lethal mimic. Then treat empirically; do not wait for NAAT results.
• The regimen to memorize: ceftriaxone IM plus doxycycline plus metronidazole for outpatients (CDC 2021). Metronidazole is now part of the standard regimen — a stem offering ceftriaxone plus doxycycline alone is the outdated distractor.
• Persistent fever after 48–72 hours of appropriate antibiotics = tubo-ovarian abscess until proven otherwise; order transvaginal ultrasound. Sudden peritonitis with hypotension = rupture, and the answer is the operating room, not more antibiotics.
• The association examiners love: Fitz-Hugh-Curtis syndrome — right upper quadrant pain in a woman with PID, normal LFTs, and violin-string perihepatic adhesions. Now more often chlamydial than gonococcal.
• IUDs: do not reflexively remove the device in a woman with PID; treat first and reassess. "Remove the IUD immediately" is a classic wrong answer.
• Pregnancy changes everything: pregnant patients with PID are admitted for parenteral therapy; doxycycline and fluoroquinolones are contraindicated.
• Partner management is part of the answer: treat sexual contacts from the prior 60 days, counsel abstinence until therapy completes, screen for HIV and syphilis, and retest for gonorrhea/chlamydia at 3 months.
• Laparoscopy visualizing purulent tubal exudate is the most specific test but is not required — PID remains a clinical diagnosis, and choosing laparoscopy as the initial step in a stable patient is a trap.