Pelvic Pain in Women: Endometriosis vs. Interstitial Cystitis - How to Tell Them Apart

For many women, chronic pelvic pain isn’t just a symptom-it’s a life-altering mystery. Two conditions, endometriosis and a condition where the bladder wall becomes inflamed, causing pain, urgency, and frequency without infection, are often mistaken for each other. They share nearly identical symptoms: pain during sex, frequent urination, burning when peeing, and deep aches in the lower belly. But they’re not the same. And confusing them can cost years of suffering.

What You’re Really Feeling

Endometriosis happens when tissue like the uterine lining grows outside the uterus-on the ovaries, bowel, bladder, or even the diaphragm. It reacts to hormones, so pain often spikes right before or during your period. Up to 92% of women with endometriosis report cyclical pain that follows their menstrual cycle. Some also notice blood in their urine during menstruation, especially if lesions are on the bladder.

Interstitial cystitis (IC), also called painful bladder syndrome, doesn’t follow your cycle. The pain is usually constant, though it can get worse around your period. It’s not caused by infection, but the bladder wall becomes irritated and inflamed. Women with IC often feel the urgent need to pee-even if they just went-and can’t hold it long. Bladder capacity drops. Normal bladders hold 400-600 mL. IC patients average 300-400 mL, and pain kicks in way before that.

The Overlap That Tricks Doctors

A 2011 study of 178 women with chronic pelvic pain found that 65% had both endometriosis and IC at the same time. That’s not rare-it’s the norm. In fact, women with endometriosis are up to four times more likely to develop IC. This is why so many women get misdiagnosed.

Doctors often start with the bladder. If you’re peeing a lot and it burns, you’re sent for a urine test. If it’s clean, you’re told you have IC. But what if the real problem is endometriosis growing on your bladder wall? That happens in 1-12% of endometriosis cases. And when it does, the symptoms look exactly like IC. A 2022 study from Hofstra Northwell found that up to 80% of patients diagnosed with IC actually had undiagnosed endometriosis.

One woman on Reddit shared her story: after seven years of IC treatment, her third laparoscopy revealed stage IV endometriosis on her bladder. Within months, her urinary symptoms dropped by 80%. She wasn’t alone. A 2022 survey of 1,243 endometriosis patients found that 68% were first diagnosed with IC.

How You Get Diagnosed

Endometriosis diagnosis is surgical. The only way to confirm it is through laparoscopic surgery, where a surgeon removes tissue and sends it to a lab. It’s not a simple procedure. In the U.S., it costs between $5,000 and $15,000. Recovery takes 2-4 weeks. And only about 15% of OB/GYNs in the U.S. are trained in the deep excision technique needed to fully remove it.

IC diagnosis is the opposite. There’s no single test. It’s a diagnosis of exclusion. First, you need to rule out infections, bladder cancer, sexually transmitted infections, and even kidney stones. Then comes cystoscopy-where a camera looks inside the bladder. Sometimes, a potassium sensitivity test (PST) is done. It’s not perfect. It’s 80% sensitive, but 20% of IC cases get missed. And if you have endometriosis on your bladder, the PST might look normal because the pain comes from nerve irritation, not bladder inflammation.

The PUF (Pelvic Pain and Urgency/Frequency) scale is often used. A score of 8 or higher suggests IC. But if you have both conditions, the score might be high because of endometriosis, not IC. That’s why doctors who only look at the bladder are missing half the picture.

Why You’re Still in Pain After Treatment

Many women go through years of treatments that don’t work because they’re treating the wrong thing. If you’re on Elmiron (the only FDA-approved IC drug), but your pain is actually from endometriosis, you’re wasting time and risking side effects. Elmiron has been linked to retinal damage in 23% of long-term users.

And pelvic floor dysfunction? It’s everywhere. A 2023 review found that 92% of women with either endometriosis or IC have tight, overactive pelvic floor muscles. These muscles aren’t just a side effect-they’re a core part of the pain. Physical therapy helps, but only if you’re also treating the root cause.

The Real Diagnostic Path

Here’s what actually works:

1. Keep a symptom diary for 3 weeks. Note pain levels, when you pee, if pain changes with your period, and if sex hurts.
2. Get a full pelvic exam. Ask for a referral to a specialist trained in endometriosis excision.
3. Rule out UTIs with urine culture-not just a dipstick test.
4. If bladder symptoms are present, get cystoscopy and consider PST-but only after ruling out endometriosis.
5. Request laparoscopy if you have cyclical pain, painful sex, or bowel/bladder symptoms during your period. Don’t wait for IC to be "confirmed."

Don’t let insurance denials stop you. A 2023 survey found 44% of women were initially denied cystoscopy. Appeal. Get a letter from your doctor. This isn’t optional-it’s essential.

What’s Changing Now

In January 2024, the Endometriosis Foundation updated its surgical guidelines: all endometriosis excision surgeries must include bladder evaluation. That’s huge. It means surgeons are finally being told to look for the overlap.

The International Pelvic Pain Society launched a dual-diagnosis protocol in 2023. It requires both a gynecologist and a urogynecologist to evaluate you together. And in February 2024, the NIH gave $4.2 million to the University of Michigan to find biomarkers that can tell these conditions apart with a simple blood or urine test.

By 2030, experts predict multidisciplinary pelvic pain centers will be standard. Right now, there are only about 350 board-certified urogynecologists in the entire U.S. Most women never see one.

Your Next Steps

If you’ve been told you have IC but still have period-related pain, deep pelvic aches, or pain during sex-you need to question that diagnosis. Ask for:

• A referral to a surgeon who specializes in endometriosis excision (not ablation)
• A full pelvic floor assessment
• A cystoscopy before committing to long-term IC treatment
• Documentation of your symptoms over time

Don’t accept being passed from gynecologist to urologist and back. The system is broken. But you don’t have to wait for it to fix itself. Start with one question: Could this be endometriosis? If the answer is yes, push for the surgery. It’s the only way to know for sure.