What are the common STIs (Sexually Transmitted Infections) in a female patient that cause yellow vaginal secretions, listed in order from least to most amount of discharge?

STIs Causing Yellow Vaginal Discharge: Ranked by Discharge Volume

Trichomoniasis produces the most profuse yellow-green discharge, followed by gonorrhea/chlamydia (mucopurulent cervicitis), while bacterial vaginosis typically causes less volume despite yellow-gray coloration. 1, 2

Ranked List by Discharge Volume

1. Trichomoniasis (Highest Volume)

• Produces diffuse, profuse, malodorous yellow-green discharge that is characteristically copious 1
• Associated with vulvar irritation and the classic "strawberry cervix" (colpitis macularis) appearance 2
• Yellow discharge is significantly associated with T. vaginalis infection (odds ratio 2.4) 2
• Purulent vaginal discharge strongly predicts trichomoniasis (odds ratio 8.0) 2
• Affects approximately 5 million cases annually in the United States 3

2. Gonorrhea and Chlamydia - Mucopurulent Cervicitis (Moderate Volume)

• Characterized by yellow or green mucopurulent endocervical discharge of moderate amount 1, 4
• Most women with gonorrhea or chlamydia do NOT have visible mucopurulent cervicitis, making discharge an insensitive marker 4
• When present, the discharge is purulent but typically less profuse than trichomoniasis 1
• Gonorrhea accounts for approximately 650,000 cases annually; chlamydia 3 million cases 3
• Critical caveat: In many cases of mucopurulent cervicitis, neither organism can be isolated—inflammation in the zone of cervical ectopy may be responsible 5, 4

3. Bacterial Vaginosis (Lower Volume)

• Produces thin, homogeneous discharge that is yellow-gray to white rather than purely yellow 1
• Volume is typically less than trichomoniasis, though the fishy odor is prominent 1
• While BV can present with yellow-tinged discharge, it is not primarily characterized by yellow coloration 6
• pH >4.5 and positive whiff test are diagnostic features 6

Important Clinical Distinctions

Non-STI Consideration

• Vulvovaginal candidiasis typically produces WHITE discharge, not yellow, and is characterized by thick, cottage cheese-like consistency 1
• Candida is the most common cause of vaginal discharge overall (17.4% prevalence) but does not cause yellow discharge 7

Diagnostic Algorithm for Yellow Discharge

• Perform wet mount microscopy immediately to identify motile trichomonads (trichomoniasis) or clue cells (bacterial vaginosis) 6
• Measure vaginal pH: normal <4.5 rules out trichomoniasis and BV; elevated pH >4.5 suggests these infections 6
• Test for gonorrhea and chlamydia using nucleic acid amplification tests (NAAT) in all patients with yellow discharge, as clinical findings are insensitive 1, 4
• Perform whiff test with KOH to detect bacterial vaginosis 6

Critical Pitfalls to Avoid

• Do not rely on discharge characteristics alone—up to 50% of women with bacterial vaginosis are asymptomatic, and most women with gonorrhea/chlamydia lack visible discharge 6, 4
• Do not continue empiric antibiotics indefinitely for persistent yellow discharge without identified pathogen—consider non-infectious cervical ectopy inflammation 5, 4
• Do not overlook co-infections—testing simultaneously for chlamydia, gonorrhea, and trichomonas is optimal for detecting treatable STIs 1
• Persistent mucopurulent discharge despite negative comprehensive STI testing may indicate inflammation in the zone of ectopy, which does not respond to antimicrobial therapy 5

Partner Management

• Treat all sexual partners from the preceding 60 days for confirmed STIs to prevent reinfection 6, 4
• Instruct abstinence from intercourse until both patient and partners complete therapy and are symptom-free 6
• Partners do not require treatment if comprehensive STI testing is negative 5