There is a version of this story that plays out thousands of times a day in doctors' offices around the world. A woman in her 20s or 30s goes to her primary care doctor with bloating, abdominal pain, and alternating diarrhea and constipation. She gets told she has IBS. She tries dietary changes, maybe a low-FODMAP diet, maybe an antispasmodic. Some things help a little. Nothing makes it go away. Years pass. Eventually, someone asks the right question or orders the right referral, and she finds out she has endometriosis. The GI symptoms were never IBS at all, or at least not only IBS. They were driven by endometrial tissue growing in places it should not be, often on or near the bowel itself. The average delay between symptom onset and endometriosis diagnosis is 7 to 10 years (Nnoaham et al., 2011). That is not a statistic about rare cases. That is the average.
Why endometriosis causes GI symptoms in the first place
Endometriosis is a condition where tissue similar to the endometrium (the lining of the uterus) grows outside the uterus. These implants most commonly appear on the ovaries, fallopian tubes, and pelvic peritoneum, but they also frequently involve the gastrointestinal tract. The rectosigmoid colon is the most common GI location, followed by the rectum, ileum, appendix, and cecum (Remorgida et al., 2007). When endometrial implants grow on or into the bowel wall, they cause direct mechanical and inflammatory effects that produce genuine GI symptoms.
But even when endometriosis does not directly involve the bowel, it can still cause significant GI symptoms. Endometriosis creates a chronic inflammatory environment in the pelvis. Pro-inflammatory cytokines, prostaglandins, and immune mediators released by endometrial implants can affect nearby structures, including the intestines. This inflammation can alter gut motility, increase visceral sensitivity (making normal gut activity feel painful), and disrupt the local immune environment. A 2009 study by Maroun et al. found that up to 90% of women with endometriosis reported at least one GI symptom, regardless of whether they had documented bowel involvement.
The cyclical nature of endometriosis is key. Endometrial implants respond to the same hormonal fluctuations as the uterine lining. During menstruation, when estrogen and progesterone drop, these implants can bleed, swell, and become inflamed. This is why many women with endometriosis notice that their GI symptoms worsen predictably around their period. That cyclical pattern is one of the most important clues that distinguishes endometriosis-related GI symptoms from typical IBS.
The symptom overlap between endometriosis and IBS
The reason endometriosis gets misdiagnosed as IBS is that the symptom profiles are nearly identical on paper. Both conditions can cause bloating, abdominal cramping, diarrhea, constipation, nausea, and pain with bowel movements. Both are more common in women. Both can be intermittent and unpredictable. And both lack a simple, definitive diagnostic test that a primary care doctor can order in a single visit.
IBS is diagnosed using the Rome IV criteria, which are symptom-based. There is no blood test, imaging study, or biopsy that confirms IBS. It is diagnosed when someone has recurrent abdominal pain associated with defecation and changes in stool frequency or form, after other conditions have been excluded. The problem is that 'other conditions' often does not include a thorough evaluation for endometriosis, particularly when the presenting complaint is GI-focused rather than gynecological.
Ballard et al. published a study in 2006 in Fertility and Sterility showing that a substantial proportion of women who were eventually diagnosed with endometriosis had previously received a diagnosis of IBS. The study highlighted that the GI symptoms of endometriosis were frequently managed as a primary GI condition for years before the correct diagnosis was made. This is not because doctors are careless. It is because the diagnostic framework for IBS does not inherently prompt evaluation for endometriosis, and many GI providers are not trained to screen for it.
⚠️If you have been diagnosed with IBS but your symptoms follow a clear menstrual pattern, worsen significantly during your period, or are accompanied by pelvic pain, painful intercourse, or pain with bowel movements, raise endometriosis as a possibility with your provider. You may need a referral to a gynecologist with endometriosis expertise rather than continuing GI-focused management alone.
The role of gut dysbiosis in endometriosis
Emerging research suggests that the relationship between endometriosis and the gut goes beyond symptom overlap. The gut microbiome itself may play a role in endometriosis development and progression. Ata et al. published a study in 2019 in Human Reproduction showing that women with endometriosis had significantly different gut microbiome compositions compared to women without the condition, with reduced bacterial diversity and alterations in specific bacterial taxa.
There are two proposed mechanisms by which gut dysbiosis could promote endometriosis. The first is through the estrobolome, the collection of gut bacteria that produce beta-glucuronidase and influence estrogen recirculation. Since endometriosis is an estrogen-dependent disease, increased estrogen recirculation from an overactive estrobolome could provide additional fuel for endometrial implant growth and survival (Plottel and Blaser, 2011). The second mechanism involves immune dysregulation. The gut microbiome is a major regulator of systemic immune function, and dysbiosis can promote chronic low-grade inflammation through increased intestinal permeability and bacterial lipopolysaccharide (LPS) translocation. This inflammatory state may create a permissive environment for endometrial implants to establish and grow.
It is important to be clear about the current state of evidence. These mechanisms are biologically plausible and supported by observational data, but we do not have proof that gut dysbiosis causes endometriosis, and no microbiome-targeted intervention has been shown to treat or prevent endometriosis in clinical trials. The relationship may also be bidirectional: endometriosis-driven inflammation and hormonal changes could alter the gut microbiome just as easily as the reverse.
The 7 to 10 year diagnostic delay and what drives it
The diagnostic delay for endometriosis is one of the longest of any common chronic condition. A landmark multicenter study by Nnoaham et al. in 2011, spanning 10 countries, found an average delay of 6.7 years from symptom onset to surgical diagnosis. Other studies have reported delays of up to 10 to 12 years in some healthcare systems. Several factors drive this.
- Normalization of pain. Many women are told that severe period pain is normal, leading them to delay seeking care or to accept reassurance that nothing is wrong.
- Symptom fragmentation. GI symptoms get reported to a gastroenterologist, pelvic pain to a gynecologist, and back pain to a primary care doctor. No single provider sees the full picture.
- Lack of a non-invasive diagnostic test. The gold standard for endometriosis diagnosis remains surgical visualization via laparoscopy with histological confirmation. There is no blood test, stool test, or imaging study that reliably diagnoses all stages of endometriosis. MRI and transvaginal ultrasound can detect deep infiltrating endometriosis and endometriomas, but they miss superficial implants.
- IBS as a diagnostic anchor. Once a patient receives an IBS diagnosis, subsequent providers may accept it without reassessing the underlying cause, especially if the patient partially responds to IBS treatments.
- Gender bias in pain assessment. Research consistently shows that women's pain reports are more likely to be attributed to psychological causes or minimized compared to men's reports (Samulowitz et al., 2018).
The consequences of delayed diagnosis are not trivial. Endometriosis can progress over time, with implants deepening and potentially causing adhesions, organ damage, and fertility problems. While earlier diagnosis does not guarantee better outcomes (we lack definitive evidence that early treatment prevents progression), it does mean earlier access to appropriate pain management, hormonal therapy, and surgical options when needed.
What helps with identifying the right diagnosis
If you suspect that your GI symptoms might be related to endometriosis, there are concrete steps you can take to move toward the right diagnosis. The most important thing is connecting your GI symptoms to your menstrual cycle in a way that is visible and documentable.
Track your GI symptoms alongside your cycle for at least three consecutive months. Note which symptoms occur, when they occur relative to menstruation, and how severe they are. A tracking tool like GLP1Gut can help you log these symptoms daily and identify cyclical patterns over time. When you bring three months of data showing that your bloating and diarrhea consistently spike around menstruation, it changes the clinical conversation from vague complaints to a recognizable pattern.
- Document the cyclical nature of your symptoms. Note whether GI problems worsen in the days before and during menstruation and improve mid-cycle.
- Report all symptoms together, not in isolation. Tell your provider about GI symptoms, pelvic pain, painful intercourse, painful urination, and fatigue together, even if you think they are unrelated.
- Ask specifically about endometriosis. Many providers will not raise it unless asked, particularly in a GI-focused visit.
- Request a referral to a gynecologist with endometriosis expertise, not just a general gynecologist. Endometriosis specialists are more likely to recognize atypical presentations and recommend appropriate diagnostic workup.
- Understand the diagnostic process. Imaging (MRI or specialized transvaginal ultrasound) can detect some forms of endometriosis but not all. A normal ultrasound does not rule out endometriosis. Definitive diagnosis often requires laparoscopy.
Can IBS and endometriosis co-exist?
Yes, and this complicates things further. Having endometriosis does not mean you cannot also have IBS. The chronic inflammation and visceral sensitization caused by endometriosis can actually trigger IBS-like changes in gut function that persist even after endometriosis is treated. Some researchers have proposed that endometriosis-associated inflammation may sensitize the enteric nervous system, creating a secondary functional GI disorder on top of the structural disease.
In clinical practice, this means that surgical treatment of endometriosis does not always resolve GI symptoms completely. Some women experience significant improvement in GI symptoms after excision surgery. Others find that while pelvic pain improves, the bloating and altered bowel habits persist. This does not mean the surgery failed. It may mean that the endometriosis triggered changes in gut function that now have their own momentum. Managing both conditions, the endometriosis through hormonal therapy or surgery and the functional GI symptoms through dietary and motility-focused approaches, often produces the best outcomes.
The key point is that endometriosis should be actively considered and ruled out before settling on an IBS diagnosis in any woman with cyclical GI symptoms and pelvic pain. Treating IBS when the underlying driver is endometriosis will always produce incomplete results.
Can endometriosis be diagnosed without surgery?
As of 2026, there is no widely validated non-invasive test that definitively diagnoses all forms of endometriosis. MRI and specialized transvaginal ultrasound can detect endometriomas and deep infiltrating endometriosis with reasonable accuracy, but they miss superficial peritoneal implants. Several biomarker-based blood tests are in development, but none has reached routine clinical use. Laparoscopy with histological confirmation remains the gold standard.
Does diet affect endometriosis symptoms?
Some women report improvement in endometriosis-related GI symptoms with dietary modifications, including reduced inflammatory foods, lower gluten intake, or anti-inflammatory dietary patterns. A small randomized trial by Nodler et al. (2020) suggested benefit from a low-FODMAP diet for endometriosis GI symptoms, but the evidence base is limited. Dietary changes may help manage symptoms but do not treat the underlying disease.
What is the difference between endometriosis on the bowel and near the bowel?
Endometriosis can be superficial (sitting on the peritoneal surface near the bowel), deeply infiltrating (growing into the bowel wall), or it can form an endometrioma (a cyst, though these are more common on ovaries). Deep infiltrating bowel endometriosis is more likely to cause severe, specific GI symptoms like rectal bleeding during menstruation, painful bowel movements, and narrowing of the bowel. Superficial endometriosis near the bowel can still cause GI symptoms through inflammation and nerve irritation.