Medical School · Year 3 · Obgyn · includes a quiz and discussion video

Seminar 17: STIs and Pelvic Inflammatory Disease

OB/GYN Clerkship

Learning Objectives

By the end of this seminar, students will be able to:

1. Identify the epidemiology, clinical presentation, and diagnostic approach for chlamydia, gonorrhea, syphilis, and genital herpes
2. Apply current CDC treatment guidelines for common sexually transmitted infections including first-line and alternative regimens
3. Diagnose pelvic inflammatory disease using minimum clinical criteria and differentiate outpatient from inpatient management indications
4. Describe the acute and long-term complications of untreated STIs including tubal infertility, ectopic pregnancy, and congenital infections
5. Formulate evidence-based STI screening strategies for different patient populations including pregnant women, adolescents, and high-risk groups
6. Counsel patients on STI prevention measures, partner notification, expedited partner therapy, and treatment compliance

Seminar Outline

Section 1: Overview and Epidemiology of Sexually Transmitted Infections

Sexually transmitted infections represent a major public health burden worldwide, with hundreds of millions of new cases diagnosed annually. Among bacterial STIs, Chlamydia trachomatis is the most commonly reported in the United States, followed by Neisseria gonorrhoeae, with rates of both infections remaining persistently elevated particularly in young women under age 25. Syphilis, caused by Treponema pallidum, has experienced a resurgence in recent decades with rising rates across multiple demographic groups including women of reproductive age, raising concerns about congenital syphilis. Among viral STIs, human papillomavirus is the most prevalent, affecting the majority of sexually active individuals at some point, while herpes simplex virus is the most common cause of genital ulcer disease.

Risk factors for acquiring sexually transmitted infections are well characterized and inform targeted screening strategies. Age is the strongest demographic predictor, with the highest rates of chlamydia and gonorrhea occurring in individuals under 25 years, reflecting both biological susceptibility of the immature cervical epithelium and behavioral factors. Multiple sexual partners and inconsistent condom use increase the probability of exposure to infected individuals. Prior history of an STI is a strong predictor of future infection due to both ongoing risk behavior and the potential for reinfection from untreated partners. Substance use, particularly alcohol and illicit drugs, is associated with impaired judgment and risky sexual behavior, further elevating STI acquisition risk.

Screening recommendations for sexually transmitted infections vary by age, sex, pregnancy status, and risk profile. The CDC and USPSTF recommend annual screening for chlamydia and gonorrhea in all sexually active women under age 25, as well as older women with risk factors such as new or multiple partners. Pregnant women should be screened at the first prenatal visit for syphilis, HIV, hepatitis B surface antigen, chlamydia, and gonorrhea, with repeat syphilis and gonorrhea testing in the third trimester for those at continued risk. Men who have sex with men should receive comprehensive STI screening at least annually, including syphilis serology, HIV testing, and site-specific chlamydia and gonorrhea NAAT testing. More frequent screening, every 3 to 6 months, is recommended for individuals with multiple partners, HIV-positive status, or ongoing high-risk behaviors.

The clinical approach to a patient with suspected STI begins with a thorough sexual history that addresses sexual practices, number and sex of partners, contraceptive use, prior STI history, and current symptoms. Physical examination should include inspection of the external genitalia, speculum examination for cervical discharge and lesions, bimanual examination for pelvic tenderness, and when indicated, oral and rectal examination. Diagnostic testing is guided by symptoms, examination findings, and risk assessment, with nucleic acid amplification testing serving as the preferred modality for chlamydia and gonorrhea detection. Treatment is frequently initiated empirically while awaiting test results, particularly in symptomatic patients or those with high pretest probability. Comprehensive management includes partner notification and treatment, counseling on risk reduction, follow-up testing, and reporting to public health authorities as required by law.

<image>Panel A: Bar graph comparing annual incidence rates of chlamydia, gonorrhea, syphilis, and genital herpes in the United States stratified by age group and sex. Panel B: Flowchart depicting the clinical approach to STI evaluation including history, examination, diagnostic testing, empiric treatment, and partner management steps. Panel C: Table of CDC-recommended STI screening intervals by population including sexually active women under 25, pregnant women, men who have sex with men, and HIV-positive individuals. Panel D: Anatomic diagram illustrating common sites of STI infection in women including cervix, urethra, pharynx, and rectum with corresponding specimen collection techniques.</image>

Section 2: Chlamydia

Chlamydia trachomatis is an obligate intracellular bacterium that causes the most commonly reported bacterial sexually transmitted infection in the developed world. The organism exists in multiple serovars, with serovars D through K responsible for urogenital, rectal, and pharyngeal infections, and serovars L1 through L3 causing lymphogranuloma venereum, a more invasive form of chlamydial disease. Transmission occurs through direct mucosal contact during vaginal, anal, or oral sexual activity, and vertical transmission from mother to neonate during delivery can cause ophthalmia neonatorum and neonatal pneumonia. The intracellular life cycle of C. trachomatis, alternating between the infectious elementary body and the metabolically active reticulate body, contributes to the organism's ability to evade host immune responses and establish persistent infection.

The clinical presentation of chlamydial infection is notable for its high rate of asymptomatic carriage, with up to 70 percent of infected women and 50 percent of infected men experiencing no symptoms. When symptomatic, cervical infection may produce mucopurulent endocervical discharge, intermenstrual bleeding, or postcoital spotting. Urethral involvement presents with dysuria and urinary frequency that may mimic a urinary tract infection. Rectal infection, increasingly recognized in women as well as men who have sex with men, manifests as proctitis with rectal pain, discharge, and bleeding. Pharyngeal chlamydia is typically asymptomatic. The asymptomatic nature of the majority of infections underscores the critical importance of screening, as untreated chlamydia can ascend to cause pelvic inflammatory disease, tubal scarring, infertility, and ectopic pregnancy.

Diagnosis of chlamydial infection relies on nucleic acid amplification testing, which has become the gold standard due to its superior sensitivity exceeding 90 percent and high specificity. NAAT can be performed on a variety of specimen types including endocervical swabs, vaginal swabs (including self-collected), urine, rectal swabs, and pharyngeal swabs. Self-collected vaginal swabs have demonstrated equivalent sensitivity to clinician-collected specimens, facilitating patient-centered screening approaches. Point-of-care rapid tests are available but have lower sensitivity than NAAT and are not recommended as a primary diagnostic modality. Culture is rarely performed for routine diagnosis but may be necessary in medicolegal cases such as sexual assault evaluation where chain of custody and specificity are paramount.

Current CDC treatment guidelines recommend doxycycline 100 milligrams orally twice daily for 7 days as the preferred first-line regimen for uncomplicated urogenital, rectal, and pharyngeal chlamydial infection. Azithromycin 1 gram orally as a single dose, previously considered a first-line alternative, has been downgraded to alternative status due to evidence of lower efficacy particularly for rectal infection. In pregnancy, azithromycin 1 gram orally as a single dose remains the preferred treatment, as doxycycline is contraindicated. Test of cure is recommended only in pregnant patients at 3 to 4 weeks after treatment, and retesting for reinfection is recommended in all treated patients at approximately 3 months regardless of whether partners were treated. Expedited partner therapy, the practice of providing prescriptions or medications to sexual partners of diagnosed patients without requiring a clinical evaluation, is an important strategy for reducing reinfection rates and is legal in most jurisdictions.

<image>Panel A: Electron micrograph of Chlamydia trachomatis elementary bodies and reticulate bodies within an infected host cell illustrating the intracellular life cycle. Panel B: Speculum examination photograph showing mucopurulent endocervical discharge and cervical friability consistent with chlamydial cervicitis. Panel C: Diagram of NAAT specimen collection sites including endocervical swab, vaginal self-swab, urine, rectal swab, and pharyngeal swab with comparative sensitivity data. Panel D: Treatment algorithm for chlamydial infection displaying preferred doxycycline regimen, azithromycin alternative, pregnancy modifications, and partner management steps.</image>

Section 3: Gonorrhea

Neisseria gonorrhoeae is a gram-negative diplococcus that causes the second most commonly reported bacterial sexually transmitted infection and presents increasing therapeutic challenges due to progressive antimicrobial resistance. The organism has a remarkable capacity for genetic adaptation, having developed resistance to sulfonamides, penicillins, tetracyclines, and fluoroquinolones over successive decades, leaving cephalosporins as the last reliable class of antibiotics for empiric treatment. Transmission occurs through sexual contact with infected mucosal surfaces, and the organism can infect the cervix, urethra, rectum, pharynx, and conjunctivae. Vertical transmission during delivery causes ophthalmia neonatorum, a sight-threatening neonatal conjunctivitis that is prevented by routine prophylactic application of erythromycin ointment to newborn eyes.

The clinical presentation of gonococcal infection in women frequently involves the cervix, producing purulent endocervical discharge, cervicitis with erythema and friability, and intermenstrual or postcoital bleeding. Urethritis presents with dysuria and frequency, while rectal infection may cause proctitis or remain asymptomatic. Pharyngeal gonorrhea is usually asymptomatic but is important to diagnose because it serves as a reservoir for transmission and is more difficult to eradicate with standard treatment. Disseminated gonococcal infection occurs when the organism enters the bloodstream and can manifest as a characteristic triad of migratory polyarthralgia or septic arthritis, dermatitis with scattered pustular or necrotic skin lesions, and tenosynovitis, typically affecting the wrists and fingers. This potentially serious complication occurs more frequently in women, particularly during menstruation or pregnancy.

Diagnosis of gonorrhea relies primarily on nucleic acid amplification testing, which offers superior sensitivity and specificity compared with culture and is the preferred modality for screening and diagnosis at all anatomic sites. However, gonococcal culture retains an important role for antimicrobial susceptibility testing, which is essential for monitoring resistance patterns and guiding treatment of resistant infections. Specimen collection sites should be determined by sexual exposure history, with endocervical, pharyngeal, and rectal specimens obtained as appropriate. Co-testing for chlamydia is always recommended given the high rate of concurrent infection, estimated at 20 to 40 percent in women with gonorrhea. Gram stain of urethral discharge in symptomatic men showing intracellular gram-negative diplococci has high sensitivity and specificity, but this technique is less reliable for cervical, rectal, and pharyngeal specimens.

The current CDC-recommended treatment for uncomplicated gonorrhea is ceftriaxone 500 milligrams intramuscularly as a single dose for patients weighing less than 150 kilograms, with the dose increased to 1 gram for patients weighing 150 kilograms or more. If chlamydial co-infection has not been excluded by testing, doxycycline 100 milligrams orally twice daily for 7 days should be added. For patients with severe cephalosporin allergy, alternative regimens include dual therapy with azithromycin plus gentamicin, though these alternatives should be used in consultation with current CDC guidelines due to evolving resistance patterns. Test of cure is recommended for pharyngeal infections at 7 to 14 days after treatment because of the higher treatment failure rate at this site, and retesting at 3 months is recommended for all treated patients to detect reinfection. All sexual partners from the preceding 60 days should be evaluated and treated presumptively.

<image>Panel A: Gram stain microscopy image showing intracellular gram-negative diplococci within polymorphonuclear leukocytes characteristic of Neisseria gonorrhoeae infection. Panel B: Clinical photograph of disseminated gonococcal infection showing scattered pustular skin lesions on the dorsum of the hand with surrounding erythema. Panel C: Timeline graphic illustrating the progressive development of antimicrobial resistance in Neisseria gonorrhoeae from sulfonamides through fluoroquinolones to emerging cephalosporin resistance. Panel D: Treatment algorithm for uncomplicated gonorrhea showing weight-based ceftriaxone dosing, chlamydia co-treatment decision, and follow-up testing schedule.</image>

Section 4: Syphilis

Syphilis is a systemic sexually transmitted infection caused by the spirochete Treponema pallidum subspecies pallidum that progresses through distinct clinical stages if left untreated. Primary syphilis manifests 10 to 90 days after exposure as a painless, indurated ulcer called a chancre at the site of inoculation, which may be located on the vulva, vagina, cervix, anus, or oropharynx. The chancre has a clean base and raised, firm borders, is highly infectious, and resolves spontaneously within 3 to 6 weeks without treatment. Secondary syphilis develops 4 to 10 weeks after the primary chancre and presents with widespread systemic manifestations including a diffuse maculopapular rash characteristically involving the palms and soles, condylomata lata (moist, flat, wart-like lesions in the anogenital region), mucous patches in the oral cavity, generalized lymphadenopathy, fever, malaise, and hepatitis.

Following resolution of secondary symptoms, untreated syphilis enters a latent phase divided into early latent (less than one year from acquisition) and late latent (more than one year or unknown duration). Latent syphilis is asymptomatic but serologically reactive. Tertiary syphilis, which develops in approximately one-third of untreated patients after years to decades, manifests as gummatous disease with destructive granulomatous lesions of the skin, bones, and organs, cardiovascular syphilis with aortitis and aortic aneurysm, or neurosyphilis with tabes dorsalis and general paresis. Neurosyphilis can also occur at any stage of infection and should be considered in patients with neurologic symptoms including headache, cranial nerve palsies, meningitis, stroke, or cognitive decline.

Diagnosis of syphilis requires serologic testing, with two complementary approaches available. The traditional algorithm uses a nontreponemal test such as RPR or VDRL for screening, followed by a treponemal confirmatory test such as FTA-ABS or TP-PA. Nontreponemal tests are quantitative and correlate with disease activity, making them useful for monitoring treatment response, while treponemal tests remain positive for life after infection regardless of treatment. The reverse sequence algorithm, increasingly adopted by large laboratories, screens with a treponemal test first, followed by confirmatory nontreponemal testing. Discordant results, particularly a positive treponemal test with negative nontreponemal test, require additional testing with a second treponemal test to resolve. Darkfield microscopy can provide immediate diagnosis by direct visualization of motile spirochetes from primary chancre fluid, though this technique is not widely available.

Treatment of syphilis depends on the stage of infection, with penicillin serving as the cornerstone of therapy across all stages. Primary, secondary, and early latent syphilis are treated with a single intramuscular injection of benzathine penicillin G 2.4 million units. Late latent syphilis and syphilis of unknown duration require three weekly injections of benzathine penicillin G 2.4 million units. Neurosyphilis demands more intensive treatment with aqueous crystalline penicillin G administered intravenously for 10 to 14 days. In pregnancy, syphilis poses grave risks including spontaneous abortion, stillbirth, hydrops fetalis, and congenital syphilis with multisystem neonatal disease. Penicillin is the only proven effective treatment in pregnancy, and penicillin-allergic pregnant patients must undergo desensitization followed by penicillin treatment. The Jarisch-Herxheimer reaction, a febrile response occurring within hours of treatment due to release of inflammatory mediators from dying spirochetes, may occur and requires monitoring, particularly in pregnancy where it can trigger preterm labor.

<image>Panel A: Clinical photograph of a primary syphilitic chancre showing a painless, clean-based ulcer with raised indurated borders on the vulvar surface. Panel B: Clinical photograph of secondary syphilis demonstrating a diffuse maculopapular rash on the palms and soles alongside oral mucous patches. Panel C: Flowchart comparing the traditional syphilis screening algorithm (nontreponemal screen then treponemal confirmation) with the reverse sequence algorithm (treponemal screen then nontreponemal confirmation) including management of discordant results. Panel D: Treatment summary diagram showing benzathine penicillin regimens by stage and the approach to neurosyphilis and pregnancy with dosing, routes, and monitoring parameters.</image>

Section 5: Genital Herpes

Genital herpes is a lifelong viral infection caused by herpes simplex virus types 1 and 2, with HSV-2 historically responsible for the majority of genital infections, though HSV-1 has become an increasingly common cause of genital herpes, particularly among young adults. Both types establish latency in the sacral sensory ganglia following primary infection and can reactivate periodically, causing recurrent outbreaks. HSV-2 genital infections tend to recur more frequently than HSV-1 genital infections, with a median of 4 to 6 recurrences annually for HSV-2 versus approximately 1 recurrence per year for HSV-1. Transmission occurs through direct skin-to-skin or mucous membrane contact, and importantly, asymptomatic viral shedding accounts for a significant proportion of transmission events, occurring on approximately 10 percent of days in HSV-2-infected individuals even in the absence of visible lesions.

The primary episode of genital herpes is typically the most severe clinical manifestation, presenting with multiple bilateral, painful vesicles and ulcers on the external genitalia, perianal area, or cervix, accompanied by systemic symptoms including fever, malaise, myalgia, and tender inguinal lymphadenopathy. The vesicles rupture to form shallow, painful ulcers that gradually crust and heal over 2 to 4 weeks. Recurrent episodes are generally milder, with fewer unilateral lesions, shorter duration of 5 to 10 days, and absent or minimal systemic symptoms. Many patients experience a prodromal phase of tingling, burning, or shooting pain in the affected dermatome hours to days before the appearance of visible lesions. Atypical presentations are common and include fissures, linear erosions, or small areas of erythema that may be misdiagnosed as candidiasis, bacterial vaginosis, or contact dermatitis.

The preferred diagnostic test for genital herpes in patients with active lesions is polymerase chain reaction, which has become the gold standard due to its superior sensitivity compared with viral culture, detecting HSV DNA even in crusted or healing lesions that may yield negative cultures. Viral culture, while less sensitive, can provide type-specific identification and is still used in some settings. Type-specific serologic testing for HSV-1 and HSV-2 IgG antibodies is useful for diagnosing prior infection in patients without active lesions, confirming HSV type in those with recurrent symptoms, and counseling asymptomatic partners of infected individuals. However, serology cannot determine the anatomic site of infection and should not be used for routine screening of asymptomatic individuals due to the potential for false positives and the psychological impact of diagnosis. Seroconversion typically occurs within 2 to 12 weeks of primary infection.

Treatment of genital herpes utilizes nucleoside analogue antiviral medications that inhibit viral DNA polymerase and reduce symptom duration, viral shedding, and recurrence frequency. For a first clinical episode, acyclovir 400 milligrams orally three times daily for 7 to 10 days, valacyclovir 1 gram twice daily for 7 to 10 days, or famciclovir 250 milligrams three times daily for 7 to 10 days are all effective options. Episodic treatment of recurrences, initiated within 24 hours of symptom onset or during the prodrome, uses shorter courses such as acyclovir 800 milligrams three times daily for 2 days. Daily suppressive therapy with acyclovir 400 milligrams twice daily or valacyclovir 500 milligrams daily is recommended for patients with frequent recurrences (6 or more per year) and reduces transmission to uninfected partners by approximately 50 percent. In pregnancy, suppressive therapy is initiated at 36 weeks of gestation to reduce the risk of active lesions at delivery, and cesarean delivery is recommended when active genital herpes lesions or prodromal symptoms are present at the time of labor due to the risk of devastating neonatal herpes infection.

<image>Panel A: Clinical photograph of primary genital herpes showing multiple grouped vesicles on an erythematous base on the vulvar surface in various stages from intact vesicles to ruptured shallow ulcers. Panel B: Diagram comparing the clinical course of primary versus recurrent genital herpes episodes showing differences in lesion number, duration, systemic symptoms, and viral shedding. Panel C: Algorithm for diagnostic testing of genital herpes showing PCR for active lesions, type-specific serology for asymptomatic patients, and interpretation of discordant results. Panel D: Treatment summary showing antiviral regimens for first episode, episodic recurrence, daily suppression, and pregnancy management with dosing schedules for acyclovir, valacyclovir, and famciclovir.</image>

Section 6: Other Sexually Transmitted and Vulvovaginal Infections

Trichomoniasis is the most common nonviral sexually transmitted infection worldwide, caused by the flagellated protozoan Trichomonas vaginalis. Women with trichomoniasis may present with a profuse, frothy, yellow-green vaginal discharge with a foul odor, vulvovaginal pruritus and irritation, dysuria, and dyspareunia. The classic physical finding is the "strawberry cervix," a punctate hemorrhagic appearance of the cervical epithelium seen in approximately 2 percent of cases on unaided examination but more frequently on colposcopy. Diagnosis has traditionally relied on wet mount microscopy showing motile, flagellated organisms, but nucleic acid amplification testing is significantly more sensitive and has become the preferred diagnostic method. Treatment consists of metronidazole 500 milligrams orally twice daily for 7 days, which is now preferred over the single 2-gram dose due to higher cure rates. All sexual partners must be treated concurrently, and patients should be retested at 3 months due to high reinfection rates.

Human papillomavirus infection is the most prevalent sexually transmitted infection, with genital warts representing the visible manifestation of infection with low-risk HPV types, primarily types 6 and 11. Condylomata acuminata appear as flesh-colored, exophytic, papillomatous growths that may be single or multiple and can occur on the vulva, vagina, cervix, perineum, or perianal area. Treatment of genital warts is directed at removing visible lesions rather than eradicating HPV infection itself, as the virus persists in surrounding tissue. Patient-applied therapies include imiquimod 5 percent cream applied three times weekly for up to 16 weeks and podofilox 0.5 percent solution applied twice daily for 3 days followed by 4 days off for up to 4 cycles. Provider-administered treatments include cryotherapy with liquid nitrogen, trichloroacetic acid application, and surgical excision or laser ablation for extensive disease. HPV vaccination is the cornerstone of prevention for both genital warts and HPV-related cancers.

Bacterial vaginosis, while not a sexually transmitted infection per se, is the most common cause of vaginal discharge in reproductive-age women and is associated with sexual activity, particularly new or multiple partners. The condition results from a shift in the vaginal microbiome from the normal Lactobacillus-dominant flora to an overgrowth of anaerobic organisms including Gardnerella vaginalis, Atopobium vaginae, and various Prevotella and Mobiluncus species. The characteristic symptom is a thin, homogeneous, grayish-white vaginal discharge with a prominent fishy odor that intensifies after intercourse or exposure to alkaline substances. Diagnosis is established using the Amsel criteria, which require three of the following four findings: thin homogeneous discharge, vaginal pH greater than 4.5, positive whiff test with potassium hydroxide, and clue cells on wet mount microscopy. The Nugent scoring system, which evaluates Gram stain morphotypes, serves as the gold standard for research purposes. Treatment with metronidazole 500 milligrams orally twice daily for 7 days is first-line therapy.

Vulvovaginal candidiasis is caused by Candida species, predominantly Candida albicans, and is not considered a sexually transmitted infection but is among the most common vulvovaginal complaints. Patients present with intense vulvar pruritus and burning, a thick, white, cottage cheese-like vaginal discharge, vulvar erythema and edema, and dyspareunia. Risk factors include recent antibiotic use, diabetes mellitus, pregnancy, immunosuppression, and high-estrogen contraceptives. Diagnosis is based on clinical presentation supported by wet mount microscopy showing budding yeast cells and pseudohyphae, or culture in cases of recurrent infection to identify the species. Uncomplicated candidiasis is effectively treated with a single dose of oral fluconazole 150 milligrams or topical azole antifungals for 1 to 7 days. Recurrent vulvovaginal candidiasis, defined as four or more episodes per year, requires an induction course followed by suppressive therapy with weekly fluconazole 150 milligrams for 6 months, and species identification is important because non-albicans species such as Candida glabrata may demonstrate fluconazole resistance requiring alternative antifungal therapy.

<image>Panel A: Wet mount microscopy image showing a motile Trichomonas vaginalis organism with visible flagella alongside vaginal epithelial cells and inflammatory cells. Panel B: Clinical photograph of condylomata acuminata showing multiple flesh-colored, papillomatous genital warts on the vulvar and perineal surfaces. Panel C: Microscopy image of a clue cell from a patient with bacterial vaginosis demonstrating a vaginal epithelial cell coated with adherent coccobacilli obscuring the cell margins. Panel D: Microscopy image of budding yeast cells and pseudohyphae on potassium hydroxide preparation consistent with vulvovaginal candidiasis.</image>

Section 7: Pelvic Inflammatory Disease -- Diagnosis

Pelvic inflammatory disease is an acute infection of the upper female genital tract that encompasses endometritis, salpingitis, oophoritis, tubo-ovarian abscess, and pelvic peritonitis. The condition most commonly results from ascending infection by sexually transmitted organisms, with Chlamydia trachomatis and Neisseria gonorrhoeae identified in approximately 30 to 50 percent of cases. However, PID is frequently polymicrobial, involving vaginal anaerobes such as Bacteroides and Peptostreptococcus species, facultative gram-negative rods, genital mycoplasmas, and streptococci. The ascending infection pathway is facilitated by conditions that alter the cervical barrier, including menstruation, cervical instrumentation, and the early post-IUD insertion period within the first 3 weeks. Despite its frequency and significant reproductive consequences, PID remains underdiagnosed because many cases present with subtle or atypical symptoms.

Risk factors for pelvic inflammatory disease overlap substantially with those for STI acquisition. Young age under 25 years is the strongest demographic risk factor, reflecting both the higher prevalence of cervical chlamydia and gonorrhea in this age group and the greater cervical ectopy that facilitates ascending infection. Multiple sexual partners, prior episodes of PID, history of STI, and inconsistent barrier contraceptive use all increase risk. Recent intrauterine device insertion carries a small transient risk of PID during the first 3 weeks as cervical bacteria may be introduced into the endometrial cavity during the procedure, though the risk returns to baseline thereafter and long-term IUD use does not increase PID risk. Vaginal douching may predispose to ascending infection by disrupting normal vaginal flora and mechanically propelling bacteria into the upper tract. Conversely, oral contraceptive use may be protective by thickening cervical mucus and reducing menstrual flow.

The clinical presentation of pelvic inflammatory disease ranges from subclinical or mild symptoms to severe illness with peritonitis. The most common complaint is bilateral lower abdominal or pelvic pain that is typically dull and constant, worsened by movement or intercourse. Abnormal vaginal or cervical discharge occurs in approximately 75 percent of cases. Fever is present in less than half of patients, meaning that its absence does not exclude the diagnosis. On bimanual examination, the hallmark finding is cervical motion tenderness, also known as the chandelier sign, which reflects peritoneal inflammation. Uterine tenderness and bilateral adnexal tenderness are additional supporting findings. The clinical presentation may mimic numerous other conditions including ectopic pregnancy, appendicitis, ovarian torsion, ruptured ovarian cyst, and urinary tract infection.

Diagnosis of PID is primarily clinical and based on the CDC minimum criteria, which require only one of the following on pelvic examination in a sexually active young woman with pelvic pain: cervical motion tenderness, uterine tenderness, or adnexal tenderness. Because PID is underdiagnosed and the consequences of untreated disease are severe, the diagnostic threshold is intentionally set low to maximize sensitivity at the expense of specificity. Additional supportive criteria that increase diagnostic confidence include oral temperature above 38.3 degrees Celsius, abnormal mucopurulent cervical or vaginal discharge, elevated erythrocyte sedimentation rate or C-reactive protein, laboratory documentation of cervical chlamydia or gonorrhea infection, and elevated white blood cell count. The most specific diagnostic criteria include endometrial biopsy showing endometritis, laparoscopic visualization of inflamed, erythematous fallopian tubes, and imaging demonstrating thickened, fluid-filled tubes or tubo-ovarian abscess on transvaginal ultrasound.

<image>Panel A: Anatomic diagram of the female reproductive tract showing the ascending infection pathway from cervicitis through endometritis to salpingitis, oophoritis, and pelvic peritonitis. Panel B: Laparoscopic photograph demonstrating bilateral salpingitis with erythematous, edematous fallopian tubes and purulent exudate on the tubal surface. Panel C: Diagnostic criteria framework showing the CDC minimum criteria, supportive criteria, and specific criteria for PID diagnosis arranged in a hierarchical pyramid of diagnostic certainty. Panel D: Transvaginal ultrasound image demonstrating a thickened, fluid-filled fallopian tube (hydrosalpinx) with echogenic contents consistent with pyosalpinx in a patient with PID.</image>

Section 8: Pelvic Inflammatory Disease -- Management

Outpatient treatment of pelvic inflammatory disease is appropriate for the majority of patients who are hemodynamically stable, able to tolerate oral medications, and do not meet criteria for hospitalization. The recommended outpatient regimen consists of ceftriaxone 500 milligrams intramuscularly as a single dose to cover gonorrhea, plus doxycycline 100 milligrams orally twice daily for 14 days to cover chlamydia and other susceptible organisms, plus metronidazole 500 milligrams orally twice daily for 14 days to provide anaerobic coverage and treat any concurrent bacterial vaginosis. This triple-drug regimen reflects the polymicrobial nature of PID and the importance of covering all likely pathogens. Patients treated as outpatients must be reevaluated within 48 to 72 hours to assess clinical response, and failure to improve should prompt hospitalization and parenteral therapy.

Inpatient treatment with parenteral antibiotics is reserved for patients meeting specific hospitalization criteria. The primary parenteral regimen consists of cefotetan 2 grams intravenously every 12 hours or cefoxitin 2 grams intravenously every 6 hours, combined with doxycycline 100 milligrams orally or intravenously every 12 hours. An alternative regimen substitutes clindamycin 900 milligrams intravenously every 8 hours plus gentamicin with a loading dose followed by weight-based maintenance dosing. Parenteral antibiotics are continued until 24 to 48 hours of clinical improvement, after which patients transition to oral doxycycline 100 milligrams twice daily with or without metronidazole 500 milligrams twice daily to complete a total 14-day treatment course. Doxycycline should be administered orally rather than intravenously when possible, as intravenous doxycycline causes significant phlebitis and has no pharmacokinetic advantage over oral administration.

Indications for hospitalization in PID include surgical emergencies that cannot be excluded, such as appendicitis or ectopic pregnancy, the presence of a tubo-ovarian abscess on imaging, pregnancy, severe illness with high fever or peritoneal signs, inability to tolerate oral medications due to nausea and vomiting, failure to respond to outpatient oral therapy within 72 hours, and situations where noncompliance with outpatient treatment is anticipated. Tubo-ovarian abscess requires intravenous antibiotics and may necessitate imaging-guided percutaneous drainage or surgical intervention if the patient fails to respond to antimicrobial therapy within 48 to 72 hours. Rupture of a tubo-ovarian abscess is a surgical emergency that presents with acute peritonitis, septic shock, and hemodynamic instability requiring emergent laparotomy.

Partner management is an essential and frequently overlooked component of PID treatment. All male sexual partners from the preceding 60 days should be evaluated and treated empirically for chlamydia and gonorrhea, regardless of their own symptoms or test results. Expedited partner therapy, which involves providing prescriptions or medications directly to the patient for delivery to their partners without requiring a clinical encounter, is recommended where legally permissible and has been shown to reduce reinfection rates. Both the patient and partners should abstain from sexual intercourse until treatment of all parties is complete and symptoms have resolved. Counseling should address the infectious etiology of PID, the importance of treatment completion, the potential for reproductive sequelae, the need for STI screening of all recent partners, and strategies for future STI prevention including consistent condom use and regular screening.

<image>Panel A: Flowchart of PID treatment decision-making showing the pathway from clinical diagnosis through assessment of hospitalization criteria to outpatient versus inpatient management with specific antibiotic regimens. Panel B: Diagram showing the three-drug outpatient PID regimen with ceftriaxone single dose, doxycycline for 14 days, and metronidazole for 14 days with corresponding bacterial targets. Panel C: CT image of the pelvis showing a large, complex, multiloculated tubo-ovarian abscess requiring intravenous antibiotics and consideration for percutaneous drainage. Panel D: Timeline of PID management showing initial treatment, 48 to 72 hour reassessment, transition to oral therapy, 14-day treatment completion, and 3-month follow-up testing schedule.</image>

Section 9: Complications of Sexually Transmitted Infections

The long-term reproductive consequences of pelvic inflammatory disease represent the most significant sequelae of untreated or inadequately treated sexually transmitted infections. Tubal factor infertility occurs in approximately 10 to 15 percent of women after a single episode of PID, with the risk increasing to 25 to 35 percent after two episodes and 50 to 75 percent after three or more episodes. The mechanism involves inflammatory destruction of the tubal mucosa and fimbriae, leading to tubal occlusion, hydrosalpinx formation, and loss of the ciliated epithelium necessary for ovum transport. The risk of ectopic pregnancy is increased 6- to 10-fold following PID due to partial tubal damage that allows fertilization but impedes normal transport of the embryo to the uterine cavity. Chronic pelvic pain affects approximately 18 percent of women after PID and results from adhesion formation, chronic tubal inflammation, and pelvic congestion.

Tubo-ovarian abscess represents the most severe acute complication of pelvic inflammatory disease, occurring in approximately 15 to 30 percent of hospitalized PID patients. TOA presents with severe bilateral pelvic pain, high fever, systemic toxicity, and a tender, fixed adnexal mass palpable on bimanual examination. The diagnosis is confirmed by imaging, with transvaginal ultrasound typically demonstrating a complex, multiloculated adnexal mass with internal echoes, though CT or MRI may provide additional information regarding the extent of disease and involvement of adjacent structures. Management consists of broad-spectrum intravenous antibiotics with regimens that include anaerobic coverage. Patients who fail to improve with 48 to 72 hours of intravenous antibiotics may require image-guided percutaneous drainage or surgical intervention. Rupture of a tubo-ovarian abscess is a life-threatening surgical emergency presenting with acute peritonitis, sepsis, and hemodynamic collapse requiring emergent laparotomy, drainage, and often unilateral or bilateral salpingo-oophorectomy.

Sexually transmitted infections during pregnancy carry serious risks for both maternal and fetal health. Untreated chlamydial infection during pregnancy is associated with preterm premature rupture of membranes, preterm delivery, low birth weight, and neonatal complications including conjunctivitis and pneumonia. Gonococcal infection carries similar risks and can cause devastating ophthalmia neonatorum in the neonate if prophylaxis is not administered. Congenital syphilis, resulting from transplacental transmission of Treponema pallidum, can cause spontaneous abortion, stillbirth, hydrops fetalis, and a wide spectrum of neonatal manifestations including hepatosplenomegaly, mucocutaneous lesions, osteochondritis, snuffles, and later stigmata such as Hutchinson teeth and interstitial keratitis. Neonatal herpes, transmitted during passage through an infected birth canal, carries a mortality rate of up to 30 percent for disseminated disease and can cause encephalitis with devastating neurologic sequelae in survivors.

The long-term complications of viral sexually transmitted infections extend well beyond the reproductive tract. Human papillomavirus infection is the causative agent of cervical cancer, vulvar cancer, vaginal cancer, anal cancer, and a growing proportion of oropharyngeal cancers. Hepatitis B virus infection acquired sexually can progress to chronic hepatitis with subsequent cirrhosis and hepatocellular carcinoma in 5 to 10 percent of adults who acquire infection, though this rate is much higher in perinatally infected individuals. HIV infection leads to progressive immunodeficiency and susceptibility to opportunistic infections and malignancies, with vertical transmission to the neonate posing additional risks unless effective antiretroviral prophylaxis is provided. Neurosyphilis represents the devastating late consequence of untreated syphilis, manifesting as meningovascular disease, general paresis, or tabes dorsalis with progressive neurologic decline over years to decades.

<image>Panel A: Diagram illustrating the progressive risk of tubal infertility with successive episodes of PID showing 10 to 15 percent after one episode, 25 to 35 percent after two, and 50 to 75 percent after three or more. Panel B: Intraoperative photograph of a ruptured tubo-ovarian abscess with purulent material in the pelvis and surrounding structures obscured by inflammatory adhesions. Panel C: Clinical photograph of a neonate with congenital syphilis demonstrating characteristic mucocutaneous findings including snuffles and maculopapular rash. Panel D: Flowchart of pregnancy-related STI complications showing the specific maternal and neonatal consequences of chlamydia, gonorrhea, syphilis, herpes, and HIV infection.</image>

Section 10: Prevention and Counseling

Primary prevention of sexually transmitted infections relies on a combination of behavioral, barrier, and biomedical strategies that should be discussed with all patients during routine clinical encounters. Consistent and correct use of male latex condoms significantly reduces transmission of most STIs, though protection is incomplete for infections spread by skin-to-skin contact in areas not covered by the condom, such as herpes and HPV. HPV vaccination, ideally administered before the onset of sexual activity, provides robust protection against the HPV types responsible for the majority of genital warts and HPV-related cancers. Hepatitis B vaccination is recommended for all children and for unvaccinated adults at risk. Pre-exposure prophylaxis with tenofovir-emtricitabine for HIV prevention has transformed HIV prevention for high-risk individuals and should be discussed with patients who have HIV-positive partners, engage in condomless sex with partners of unknown status, or have other risk factors.

Secondary prevention through systematic screening and early treatment interrupts transmission chains and reduces the burden of complications. Adherence to screening guidelines, including annual chlamydia and gonorrhea testing for women under 25 and comprehensive screening for high-risk populations, enables detection and treatment of asymptomatic infections before complications develop or further transmission occurs. Early treatment of diagnosed infections reduces the duration of infectiousness and prevents progression to upper tract disease and other complications. Partner notification, whether by the patient, healthcare provider, or public health department, is a critical component of secondary prevention that ensures treatment of sexual contacts who may be unknowingly infected. Retesting at 3 months following treatment for chlamydia and gonorrhea detects reinfection, which occurs in approximately 10 to 20 percent of patients, often from untreated partners.

Effective patient counseling is a cornerstone of STI management and should be conducted with sensitivity, empathy, and without judgment. Key counseling elements include education about the specific infection, its transmission routes, and the importance of completing the full course of prescribed medication even if symptoms resolve. Patients should be counseled on the necessity of abstaining from sexual activity until treatment is complete for both themselves and their partners, to prevent ping-pong reinfection. Disclosure to current and future sexual partners should be discussed, along with available resources for partner notification. Risk reduction strategies including consistent condom use, reducing the number of sexual partners, and mutual monogamy with a tested partner should be reviewed. For patients diagnosed with herpes or HIV, counseling should address the chronic nature of infection, strategies for reducing transmission, and available support resources.

Special populations require tailored approaches to STI prevention and management. Adolescents have the highest rates of STIs and may face barriers to care including concerns about confidentiality, limited access to healthcare, and lack of awareness about risks. Providers should be aware of state laws regarding minor consent for STI services and ensure confidential, nonjudgmental care. Pregnant women require universal screening with prompt treatment to prevent perinatal transmission, and treatment selection must account for medication safety in pregnancy. HIV-positive individuals need more frequent and comprehensive screening due to increased susceptibility to STI acquisition and complications, as well as bidirectional interactions between HIV and other STIs that can increase viral load and transmission risk. Survivors of sexual assault require a comprehensive approach including empiric STI prophylaxis for gonorrhea, chlamydia, and trichomoniasis, HIV post-exposure prophylaxis if indicated, hepatitis B vaccination, emergency contraception, and follow-up testing at 2 weeks, 6 weeks, 3 months, and 6 months.

<image>Panel A: Infographic summarizing primary STI prevention strategies including abstinence, mutual monogamy, condom use, HPV vaccination, hepatitis B vaccination, and HIV PrEP with relative effectiveness data. Panel B: Diagram of the partner notification process showing patient referral, provider referral, and expedited partner therapy approaches with comparative advantages of each method. Panel C: Screening timeline for pregnant women showing recommended tests at first prenatal visit, third trimester, and delivery with specific STIs tested at each time point. Panel D: Comprehensive flowchart for sexual assault STI management showing empiric prophylaxis regimens for gonorrhea, chlamydia, trichomoniasis, and HIV along with emergency contraception and follow-up testing schedule.</image>

Summary

• Chlamydia is the most common bacterial STI, often asymptomatic in up to 70 percent of women, diagnosed by NAAT, and treated with doxycycline 100 milligrams twice daily for 7 days as the preferred regimen
• Gonorrhea demonstrates increasing antimicrobial resistance and is treated with ceftriaxone 500 milligrams intramuscularly as a single dose, with co-testing and co-treatment for chlamydia always recommended
• Syphilis progresses through primary (painless chancre), secondary (rash, condylomata lata), latent, and tertiary stages, with benzathine penicillin G as the treatment for all stages and mandatory desensitization for penicillin-allergic pregnant patients
• Genital herpes is diagnosed by PCR of active lesions, treated with nucleoside analogues, and managed with suppressive therapy from 36 weeks gestation in pregnancy with cesarean delivery if active lesions are present
• Trichomoniasis is diagnosed by NAAT (more sensitive than wet mount) and treated with metronidazole 500 milligrams twice daily for 7 days with concurrent partner treatment
• PID diagnosis requires only one minimum criterion on examination (cervical motion, uterine, or adnexal tenderness) in a sexually active woman with pelvic pain
• PID outpatient treatment consists of ceftriaxone plus doxycycline plus metronidazole for a total of 14 days with reassessment at 48 to 72 hours
• PID sequelae include tubal infertility (10 to 15 percent after one episode), 6- to 10-fold increased ectopic pregnancy risk, and chronic pelvic pain in 18 percent
• Partner treatment within 60 days is essential for STI control, with expedited partner therapy recommended where legally permissible
• Prevention strategies include screening per guidelines, consistent condom use, HPV and hepatitis B vaccination, HIV PrEP, and comprehensive treatment compliance counseling

Key Terms

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