PID is a serious infection of reproductive organs. It can cause a number of symptoms, including foul-smelling and differently-colored vaginal discharge.

The vagina is often dubbed a self-cleaning machine. That’s because, in healthy individuals, the vagina expels discharge that helps rid the canal of potentially-disruptive bacteria, dirt, and dead skin cells.

Healthy discharge is typically described as:

  • clear or milky
  • mucus-like or slimy
  • odorless

Underlying infection can cause unexpected changes in your discharge’s color, consistency, and overall odor.

PID, specifically, can cause the following changes:

  • yellow or green in color
  • heavier or thicker than usual
  • increased volume or amount than usual
  • unpleasant or fishy in odor

“The degree of these changes to vaginal discharge can be slight or significant, depending on the person,” says Michael Ingber, MD, urologist and female pelvic medicine specialist at The Center for Specialized Women’s Health in New Jersey.

It’s possible for a person to have asymptomatic PID or symptoms that are too mild to pick up on readily.

When symptoms do occur, they might include:

  • back, pelvic, or stomach pain
  • discomfort during or after vaginal penetration
  • vaginal bleeding or spotting between periods
  • painful urination or bowel movements
  • change in menstrual periods

What is the most common visible symptom of PID?

“Most of the time, pelvic inflammatory disease does not cause lumps or ulcers,” says Ingber.

Typically, if an individual has a lump, bump, or ulcer, it is because they have a sexually transmitted infection (STI) like herpes, syphilis, or genital warts, he says.

Although it’s possible to have one of these STIs and PID, these STIs do not typically cause PID — gonorrhea and chlamydia do.

PID, however, can cause discharge changes, spotting between periods, and bleeding after vaginal penetration. These symptoms can all be observed by looking at your underwear or the toilet paper after wiping.

What is the most common nonvisible symptom of PID?

Most PID symptoms are not seen but felt. For instance, it’s common for individuals to experience general pelvic pain, says Ingber.

He says this pain is commonly exacerbated during or after urination, excretion, or penetration.

What conditions can be mistaken for PID and vice versa?

“General pelvic pain is often associated with conditions such as endometriosis, interstitial, cystitis, fibromyalgia, and other pelvic and reproductive conditions,” says Ingber. As such, individuals with this symptom may have their PID mistaken for these other conditions instead.

Meanwhile, when an individual’s primary symptom is discharge changes, the condition can be wrongly diagnosed as a yeast infection or bacterial vaginosis, he says. Both of these conditions, he explains, can cause unusual discharge, too.

PID can lead to a wide variety of visible and invisible symptoms. PID can cause long-term complications like pelvic scarring, adhesions, and infertility if left untreated.

Consult a healthcare professional if you’re experiencing unusual discharge or other unexpected symptoms. They can help identify the underlying cause and recommend a plan for treatment.

Gabrielle Kassel (she/her) is a queer sex educator and wellness journalist who is committed to helping people feel the best they can in their bodies. In addition to Healthline, her work has appeared in publications such as Shape, Cosmopolitan, Well+Good, Health, Self, Women’s Health, Greatist, and more! In her free time, Gabrielle can be found coaching CrossFit, reviewing pleasure products, hiking with her border collie, or recording episodes of the podcast she co-hosts called Bad In Bed. Follow her on Instagram @Gabriellekassel.