PID or Simple STI? The PLAB 2 Approach to Recognising and Managing Pelvic Inflammatory Disease Safely

Ann Augustin
14 hours ago
3 min read

How to Differentiate, Investigate, and Manage

One of the most important PLAB 2 skills is recognising when a patient with STI symptoms may actually have Pelvic inflammatory disease rather than a simple lower genital tract infection.

This distinction is extremely important because missing PID can lead to:

Infertility
Chronic pelvic pain
Ectopic pregnancy
Tubo-ovarian abscess

A common PLAB 2 trap is treating discharge alone without identifying upper genital tract involvement.

What is the Difference?

Simple STI / Lower Genital Tract Infection

Usually limited to:

Cervix
Urethra
Vagina

Common examples:

Chlamydia cervicitis
Gonorrhea cervicitis
Trichomoniasis
Candidiasis

Pelvic Inflammatory Disease (PID)

PID occurs when infection ascends into the:

Uterus
Fallopian tubes
Ovaries
Pelvic structures

PID is usually caused by:

Chlamydia
Gonorrhea
Anaerobic/BV-associated organisms

Important Organism Clarifications

Bacterial vaginosis / Gardnerella

BV-associated anaerobes can contribute to PID.

This is why:

Metronidazole is included in PID treatment.

Trichomoniasis

Can coexist with PID and increase inflammation, but is not a classic primary PID organism.

Candidiasis

Usually does NOT cause PID and remains localized to the lower genital tract.

Symptoms: Gonorrhea/Chlamydia Cervicitis vs PID

Feature	Gonorrhea/Chlamydia Cervicitis	PID
Vaginal discharge	Common	Common
Yellow-green discharge	Common in gonorrhea	Common
Dysuria	Common	Common
Offensive smell	Possible	Possible
Pelvic/lower abdominal pain	Usually absent or mild	Important feature
Deep dyspareunia	Usually absent	Suggestive
Fever	Rare	May occur
Intermenstrual bleeding	Possible	More suggestive
Postcoital bleeding	Possible	Possible
Cervical motion tenderness	Absent	Suggestive
Adnexal tenderness	Absent	Suggestive

The Most Important Differentiating Feature

Pelvic Pain

A sexually active woman with:

discharge,
STI risk factors,
AND persistent lower abdominal/pelvic pain

should raise strong suspicion for PID.

This is the major point that shifts management away from “simple STI treatment” toward PID treatment.

PLAB 2 Clinical Principle

PID is primarily a clinical diagnosis.

Treatment should not be delayed while awaiting test results if suspicion is significant.

Clinicians maintain a low threshold for empirical treatment because delayed treatment increases the risk of infertility and chronic complications.

Investigations

Important investigations include:

STI NAAT testing
Vaginal/cervical swabs
Pregnancy test
HIV testing
Syphilis testing

When Are Antibiotics Started?

Simple STI

Sometimes treatment may wait until results return depending on symptoms and clinical suspicion.

Suspected PID

Treatment is usually started immediately after investigations are taken.

Why?

Because delaying treatment may increase the risk of:

Infertility
Ectopic pregnancy
Chronic pelvic pain

First-Line PID Treatment

Standard Outpatient Regimen

Ceftriaxone IM stat dose

PLUS
Doxycycline for 14 days

PLUS
Metronidazole for 14 days

Important Clarification

Ceftriaxone is a one-time stat injection, not a 14-day course.

Alternative Regimens

Alternative regimens may include:

Ofloxacin + metronidazole for 14 days
Moxifloxacin for 14 days in selected cases

However, quinolone resistance in gonorrhea limits routine use of ofloxacin.

Follow-Up

PID Follow-Up

Patients treated as outpatients should usually be reviewed within 72 hours.

This is recommended in UK guidance to ensure:

symptoms are improving,
antibiotics are working,
complications are not developing.

If Symptoms Are Not Improving

Consider:

Alternative diagnosis
Resistant organisms
Poor compliance
Tubo-ovarian abscess
Need for hospital admission

Where Should Follow-Up Occur?

Follow-up may occur:

With GP
Or in a Genitourinary medicine clinic / sexual health clinic

Sexual health clinics are often preferred because they can:

Review STI results
Arrange partner notification
Provide contact tracing
Offer full STI management

Partner Notification

Patients should be advised that:

Recent sexual partners may require testing and treatment
Reinfection can occur if partners are untreated

Avoid blame or assumptions when discussing transmission.

A safe explanation is:

“It is difficult to know exactly when or from whom the infection was acquired.”

Important Patient Advice

Advise the patient to:

Avoid sexual intercourse until treatment is completed and symptoms resolve
Use condoms in future
Attend follow-up appointments

Safety Netting

Seek urgent medical attention if:

Fever develops
Pain worsens
Vomiting occurs
Heavy bleeding develops
Severe pelvic pain occurs

High-Yield PLAB 2 Communication Line

“Because your symptoms may suggest an infection involving the reproductive organs, I would recommend starting treatment today rather than waiting for the test results.”

Key PLAB 2 Take-Home Message

Discharge Alone → Think Simple STI
Discharge + Pelvic Pain → Think PID Until Proven Otherwise