Residency · Residency · Obstetrics Gynecology
Pelvic Inflammatory Disease and Tubo-Ovarian Abscess
Overview
Pelvic inflammatory disease (PID) is an infection-induced inflammation of the upper female genital tract encompassing endometritis, salpingitis, oophoritis, parametritis, and pelvic peritonitis. Most cases result from ascending sexually transmitted organisms. PID represents a significant public health problem, with approximately 1 million cases annually in the United States, and is a major cause of preventable infertility, ectopic pregnancy, and chronic pelvic pain.
Microbiology
PID is polymicrobial in most cases. The primary pathogens are Neisseria gonorrhoeae, Chlamydia trachomatis, and Mycoplasma genitalium, which is increasingly recognized as an important contributor. Secondary and associated organisms include anaerobes (Bacteroides, Prevotella, Peptostreptococcus), facultative gram-negatives (E. coli, Haemophilus influenzae), vaginal flora (Gardnerella, Streptococci), and BV-associated bacteria (BVAB1-3). Importantly, N. gonorrhoeae and C. trachomatis are identified in only 30 to 50% of PID cases, and many are culture-negative, underscoring the polymicrobial nature of the disease.
Risk Factors
The highest incidence occurs in women aged 15 to 25 years. Additional risk factors include multiple sexual partners, history of STI or prior PID, inconsistent condom use, bacterial vaginosis, recent IUD insertion (with a small increased risk in the first 3 weeks, though this is not a contraindication to IUD use), uterine instrumentation (dilation and curettage, hysterosalpingography, endometrial biopsy), and cervical ectopy. Protective factors include barrier contraception (condoms), hormonal contraception (which thickens cervical mucus), and consistent screening and treatment of STIs.
Clinical Presentation
Symptoms
Lower abdominal and pelvic pain is the most common symptom, present in 95% of cases. Additional symptoms include abnormal vaginal discharge (mucopurulent), abnormal uterine bleeding (irregular or postcoital), dyspareunia, and dysuria. Nausea, vomiting, and fever suggest more severe disease. Right upper quadrant pain indicates Fitz-Hugh-Curtis syndrome, which is perihepatitis.
Physical Exam
Cervical motion tenderness is the classic finding. Uterine tenderness and adnexal tenderness, which may be unilateral or bilateral, are additional findings. Mucopurulent cervical or vaginal discharge is often present. Fever above 38.3 degrees Celsius is present in only 30 to 40% of cases, so its absence does not exclude the diagnosis. An adnexal mass or fullness suggests a tubo-ovarian abscess. Right upper quadrant tenderness indicates Fitz-Hugh-Curtis syndrome.
Diagnosis
CDC Minimum Criteria (2021)
PID should be diagnosed and treated empirically in sexually active young women with any one of the following and no other identifiable cause: cervical motion tenderness, uterine tenderness, or adnexal tenderness. The low threshold for diagnosis is intentional because underdiagnosis leads to worse long-term sequelae including infertility and ectopic pregnancy.
Additional Criteria (Increase Specificity)
Additional findings that increase diagnostic specificity include oral temperature above 38.3 degrees Celsius, mucopurulent cervical discharge, abundant white blood cells on vaginal wet mount, elevated ESR or CRP, positive NAAT for N. gonorrhoeae or C. trachomatis, positive endocervical Gram stain for gram-negative diplococci, and endometrial biopsy showing endometritis with plasma cells.
Definitive Criteria (Rarely Needed)
Definitive diagnostic criteria, which are rarely required, include laparoscopy showing salpingitis or tubal inflammation, endometrial biopsy showing endometritis, and imaging showing thickened, fluid-filled tubes (hydrosalpinx or pyosalpinx) with or without free pelvic fluid or tubo-ovarian abscess.
Imaging
Transvaginal ultrasound may be normal in mild PID. When abnormal, findings include thickened, fluid-filled fallopian tubes with the "cogwheel sign" on cross-section, free fluid in the cul-de-sac, and a complex adnexal mass representing a tubo-ovarian abscess. CT or MRI is used for equivocal cases, tubo-ovarian abscess characterization, or surgical planning.
<image>Transvaginal ultrasound images of PID complications: pyosalpinx showing a fluid-filled, thickened fallopian tube with the classic cogwheel cross-sectional appearance, tubo-ovarian abscess appearing as a complex multiloculated adnexal mass with thick walls and internal debris, and free fluid in the posterior cul-de-sac</image>
Treatment
Outpatient Treatment (Most PID Can Be Treated Outpatient)
The CDC 2021 recommended regimen consists of ceftriaxone 500 mg intramuscularly as a single dose plus doxycycline 100 mg orally twice daily for 14 days, with or without metronidazole 500 mg orally twice daily for 14 days. Metronidazole is added when BV is present, when recent uterine instrumentation has occurred, or when tubo-ovarian abscess is suspected. An alternative regimen when ceftriaxone is not available substitutes cefoxitin 2 g intramuscularly with probenecid 1 g orally as a single dose, followed by doxycycline 100 mg orally twice daily for 14 days with or without metronidazole.
| Setting | Regimen | Details |
|---|---|---|
| Outpatient (preferred) | Ceftriaxone 500 mg IM x1 + Doxycycline 100 mg PO BID x 14 days ± Metronidazole 500 mg PO BID x 14 days | Add metronidazole for BV, instrumentation, or suspected TOA |
| Outpatient (alternative) | Cefoxitin 2 g IM + Probenecid 1 g PO x1 + Doxycycline 100 mg PO BID x 14 days ± Metronidazole | When ceftriaxone unavailable |
| Inpatient (Regimen A) | Cefotetan 2 g IV q12h or Cefoxitin 2 g IV q6h + Doxycycline 100 mg q12h | Continue IV for 24 hours after improvement; complete 14 days oral |
| Inpatient (Regimen B) | Clindamycin 900 mg IV q8h + Gentamicin (2 mg/kg load then 1.5 mg/kg q8h) | Transition to oral clindamycin or doxycycline to complete 14 days |
Inpatient Treatment Criteria
Hospitalization is indicated when a surgical emergency cannot be excluded (such as appendicitis or ectopic pregnancy), when a tubo-ovarian abscess is present, when the patient is pregnant, when outpatient therapy has failed (no improvement after 48 to 72 hours), when the patient cannot tolerate or follow an outpatient regimen, when severe illness is present (high fever, nausea and vomiting, severe pain), or when the patient is immunocompromised.
Inpatient Regimens
Regimen A consists of cefotetan 2 g intravenously every 12 hours or cefoxitin 2 g intravenously every 6 hours, plus doxycycline 100 mg orally or intravenously every 12 hours. Intravenous antibiotics are continued for at least 24 hours after clinical improvement, then the patient transitions to oral doxycycline to complete 14 days with or without metronidazole. Regimen B consists of clindamycin 900 mg intravenously every 8 hours plus gentamicin with a loading dose of 2 mg/kg intravenously followed by 1.5 mg/kg every 8 hours or single daily dosing at 3 to 5 mg/kg. Transition to oral therapy uses clindamycin 450 mg orally four times daily or doxycycline 100 mg twice daily to complete 14 days.
Partner Management
All sexual partners from the past 60 days should be examined and treated. Testing for gonorrhea and chlamydia is performed, and empiric treatment with ceftriaxone plus doxycycline is administered. Expedited partner therapy should be used if the partner is unlikely to present for evaluation. The patient should abstain from intercourse until treatment is completed and partners are treated.
Tubo-Ovarian Abscess (TOA)
Definition and Pathophysiology
A tubo-ovarian abscess is an inflammatory mass involving the fallopian tube, ovary, and sometimes adjacent structures. It occurs in 15 to 35% of women hospitalized for PID. The microbiology is polymicrobial with anaerobes predominating, including Bacteroides fragilis and Peptostreptococcus, along with gram-negatives and N. gonorrhoeae or C. trachomatis. A TOA can develop even in women without a recent history of PID, arising from ascending BV flora or following procedures.
Clinical Features
Patients present with fever, chills, and pelvic pain that is often severe and unilateral. A palpable adnexal mass is not always detectable on examination. Peritoneal signs are present if the abscess is leaking or has ruptured. Laboratory findings include leukocytosis with a left shift and elevated inflammatory markers (CRP, ESR).
Imaging
On transvaginal ultrasound, a TOA appears as a complex adnexal mass with thick walls, internal echoes or debris, and septations, with loss of normal tubal and ovarian architecture forming a "tubo-ovarian complex." CT shows a ring-enhancing mass with surrounding inflammatory stranding and may demonstrate free fluid. MRI is used when ultrasound is equivocal.
Treatment
Broad-spectrum intravenous antibiotics are initiated using the same inpatient regimens as for PID, with metronidazole added for anaerobic coverage if not already included. Clinical improvement is expected within 48 to 72 hours in 70 to 75% of patients. Image-guided drainage, either percutaneous or transvaginal, is indicated when there is no clinical improvement after 48 to 72 hours of intravenous antibiotics. Abscesses larger than 6 to 8 cm may benefit from early drainage. Transvaginal drainage under ultrasound guidance is effective and minimally invasive, while percutaneous drainage is performed by interventional radiology under CT guidance. Surgical intervention is indicated for ruptured TOA (which is a surgical emergency), failed drainage, or clinical deterioration. A ruptured TOA presents with peritonitis, sepsis, and hemodynamic instability and requires emergent laparotomy or laparoscopy. The typical surgical procedure is unilateral salpingo-oophorectomy with drainage and washout. Hysterectomy with bilateral salpingo-oophorectomy is rarely needed and is reserved for severe bilateral disease, hemodynamic instability, or refractory sepsis.
<image>Management algorithm for tubo-ovarian abscess: initial IV antibiotic therapy for all patients, reassessment at 48-72 hours, if improving then transition to oral antibiotics and complete 14 days, if not improving then proceed to image-guided drainage (transvaginal or CT-guided percutaneous), and if drainage fails or TOA ruptures then surgical intervention with laparoscopy or laparotomy</image>
Long-Term Sequelae of PID
Infertility
Tubal factor infertility occurs in 8% of women after one episode of PID, 20% after two episodes, and 40% after three or more episodes. Tubal damage results from inflammation, adhesion formation, and hydrosalpinx.
Ectopic Pregnancy
The risk of ectopic pregnancy increases 6 to 10 fold after PID. Tubal damage impairs normal ovum transport through the tube.
Chronic Pelvic Pain
Chronic pelvic pain occurs in 18 to 35% of women after PID, resulting from adhesions, hydrosalpinx, and central sensitization of pain pathways.
Recurrent PID
PID recurs in 20 to 25% of cases. Each episode causes cumulative tubal damage.
Fitz-Hugh-Curtis Syndrome
Fitz-Hugh-Curtis syndrome is perihepatitis characterized by inflammation of the liver capsule with "violin string" adhesions between the liver and anterior abdominal wall. It occurs in 5 to 10% of PID cases and is more common with chlamydial infection. The right upper quadrant pain may mimic cholecystitis. Diagnosis is made on laparoscopy or CT showing liver capsule enhancement. Treatment is the standard PID antibiotic regimen.
Prevention
Prevention strategies include annual Chlamydia and gonorrhea NAAT screening for all sexually active women under 25 years and older women with risk factors, prompt treatment of lower genital tract infections (cervicitis, BV), partner treatment and expedited partner therapy, consistent condom use, and patient education regarding symptoms of PID and the importance of seeking care.
Clinical Pearls
A low diagnostic threshold should be used for PID. Undertreatment causes more harm through infertility, ectopic pregnancy, and chronic pain than overtreatment does.
The CDC minimum criteria require only one of the following in a sexually active woman without an alternative explanation: cervical motion tenderness, uterine tenderness, or adnexal tenderness.
Most PID can be treated as an outpatient. Hospitalization is reserved for tubo-ovarian abscess, severe illness, failed outpatient therapy, or uncertain diagnosis.
Doxycycline is preferred over azithromycin for PID treatment per the 2021 CDC guidelines.
Metronidazole should be added to PID regimens when BV is present, recent uterine instrumentation has occurred, or tubo-ovarian abscess is suspected.
An IUD does not need to be removed in mild PID. It can remain in place with close follow-up, though removal may be considered if there is no improvement in 48 to 72 hours.
Each episode of PID roughly doubles the risk of tubal factor infertility, making prevention and prompt treatment critical.
Ruptured tubo-ovarian abscess is a surgical emergency. Hemodynamic instability with a known TOA requires immediate intervention.
References
- CDC Sexually Transmitted Infections Treatment Guidelines (2021)
- ACOG Practice Bulletin No. 187: Acute Pelvic Inflammatory Disease (2019, reaffirmed 2023)
- Brunham RC et al. Pelvic inflammatory disease. N Engl J Med. 2015;372:2039-2048
- Landers DV, Sweet RL. Tubo-ovarian abscess: contemporary approach to management. Rev Infect Dis. 1983;5:876-884
- Workowski KA et al. CDC STI Treatment Guidelines 2021. MMWR. 2021;70(4):1-187
- Ness RB et al. Effectiveness of inpatient and outpatient treatment strategies for women with PID (PEACH trial). Am J Obstet Gynecol. 2002;186:929-937
