Endometriosis and the gut: why it so often ends up labelled IBS
The same diagnosis for years, and still the symptoms travel with your menstrual cycle. How to recognise that, why the colonoscopy usually says nothing about it, and which route leads to an answer today.
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When an irritable bowel has been there for years and the symptoms travel with the menstrual cycle, then the next sensible question is not which probiotic is still missing. The next question is whether the gut is the sick organ here at all.
By now you know your calendar better than your appointments. Not the one with the dates in it. The other one, the one you keep in your head.
The good days are the ones between the bleed and the middle. Your trousers fit then. You can have breakfast without looking five months pregnant by the evening. And then it tips over. Always at roughly the same point.
The letter from the clinic says irritable bowel syndrome. Maybe for four years, maybe for twelve. You have dropped wheat, dropped milk, dropped raw vegetables. You have tried probiotics, psyllium, peppermint oil, yoga. Some of it did something, none of it changed the pattern.
Many women know exactly this pattern. And in some of them the problem does not sit in the bowel wall, but next to it.
I am not writing this text against the diagnosis of IBS. IBS is a real diagnosis with its own criteria, not a placeholder. I am writing it because of a single question that regularly goes unasked in the IBS clinic: which day of your menstrual cycle was that, actually?
What you can expect here
- How long it takes on average to reach a diagnosis of endometriosis, with numbers
- How often endometriosis and IBS occur together
- The four features that made the difference in an IBS clinic
- Why cyclical patterns are a pointer and not a criterion
- Endo belly: the five mechanisms, sorted cleanly by strength of evidence
- Why colonoscopy finds only 7 out of 100 bowel lesions
- And why it still matters
- The route via transvaginal ultrasound, with numbers
- What hormonal treatment and surgery do to bowel symptoms
- Nutrition in three tiers: evidenced, plausible, unevidenced
Everything written here about cycle patterns only applies once these points have been clarified. They are not a reason to panic, but they are a reason for an appointment and not for a self experiment.
- Blood in the stool, or black tarry stool
- Unintended weight loss
- Fever without a recognisable infection
- Symptoms that wake you at night
- Repeated vomiting or difficulty swallowing
- A new, persistent change in bowel habit from around the age of 45 to 50
- Anaemia in the blood count
- Bowel cancer or inflammatory bowel disease in the family
- A persistent increase in abdominal girth that does not go back down overnight
- New, almost daily bloating over several weeks, especially after the menopause
- Early satiety, feeling full after only a few bites
One addition for this topic: blood in the stool that appears only during the bleed is a pointer that belongs in gynaecology. It does not replace the assessment of the other causes. A fissure, haemorrhoids, inflammatory bowel disease or a tumour can produce the same bleeding. More on that in Haemorrhoids and anal symptoms in context.
And one more thing I want to say early: severe period pain that limits your daily life is not normal. It is common. That is not the same thing.
The sentence many women hear for years
It usually comes kindly. That will be an irritable bowel, try a bit less stress.
And it is often not wrong. IBS is common, IBS is real, and most people with these symptoms have exactly that. The criteria for it are set internationally, in the Rome IV classification of functional bowel disorders. Mearin F, Lacy BE, Chang L et al. Gastroenterology. 2016;150(6):1393-1407.e5. PMID: 27144627 · DOI: 10.1053/j.gastro.2016.02.031 [Consensus Guideline] The problem is not the diagnosis. The problem is that it closes like a door.
Because a second story is running in parallel. On the figures evidenced further down, endometriosis affects around 10 to 15 percent of women of reproductive age. Scaled roughly to Germany, that puts you in the order of one to two million women. That is a rough calculation, not a survey. And between the first symptom and the moment the name appears on paper, years pass on average.
A team around Kelechi Nnoaham recorded 1,418 women at 16 centres in ten countries who underwent a laparoscopy to investigate their symptoms. This was a cross-sectional survey with prospective recruitment, not a cohort followed over years.
Between the first symptom and the surgical diagnosis lay 6.7 years. At centres with predominantly public funding it was 8.3 years, elsewhere 5.5. The delay arose mainly in primary care. And it was longer the more different pelvic symptoms a woman had. The time span was asked about retrospectively, not tracked across the years.
For you that means: your many symptoms did not help you, they slowed you down. Variety makes a picture unspecific. Whoever has everything fits into no box, and boxes are where diagnostics starts.
Nnoaham KE, Hummelshoj L, Webster P et al. Fertil Steril. 2011;96(2):366-373.e8. PMID: 21718982 · DOI: 10.1016/j.fertnstert.2011.05.090 [Cross-sectional, multicentre, n=1,418]This is where the corridor named by many German language texts comes from: in studies the average delay to diagnosis is around seven to ten years. The source for it is the figures above, 6.7 years internationally and 8.3 years in the centres with predominantly state funded care, which is where Germany sits. Depending on country and survey the value falls somewhat higher or lower.
Now comes the part this article is about. Those years are not empty. Appointments, tests and labels run through them. One of those labels is irritable bowel.
Karen Ballard and her team searched the years 1992 to 2001 of a British general practice database and compared 5,540 women with a later endometriosis diagnosis with four women each without endometriosis.
The gynaecological signs were clear, as expected: period pain with an odds ratio of 8.1, pain during sex or bleeding afterwards at 6.8, abdominal and pelvic pain at 5.2. One other value was unexpected. A diagnosis of irritable bowel syndrome already appeared in these women's records beforehand far more often, with an odds ratio of 1.6.
For you that means: you are not the only one for whom the bowel drawer opened before the pelvic drawer. The authors write explicitly that endometriosis may exist alongside an irritable bowel or be classified as one.
Ballard KD, Seaman HE, de Vries CS, Wright JT. BJOG. 2008;115(11):1382-1391. PMID: 18715240 · DOI: 10.1111/j.1471-0528.2008.01878.x [Case control, national, n=5,540]The common story goes: somebody did a bad job here. I see it differently.
The delay arises in a system where abdominal symptoms land in gastroenterology and pelvic symptoms in gynaecology, and where both specialties have their own good criteria. Between those criteria lies a gap, and in that gap sits the day of your menstrual cycle.
This is not a question of blame. It is a question of order. And you can influence that order by bringing along the information nobody else records.
Two demarcations, so you do not read the same thing twice. How an irritable bowel develops, what visceral hypersensitivity means and which causes may sit behind it is in IBS: finding the causes. And endometriosis as a disease in itself, with oestrogen, the immune system and models of its origin, is in Endometriosis: causes seen integratively. A compact specialist overview of the condition is the summary in the New England Journal of Medicine. Zondervan KT, Becker CM, Missmer SA. N Engl J Med. 2020;382(13):1244-1256. PMID: 32212520 · DOI: 10.1056/NEJMra1810764 [Review] Here it is solely about the one question of whether the diagnosis hangs on the right organ.
And now you know why the years pass without anyone doing anything wrong.
How often the two occur together, and what that number does not mean
Search online and you quickly find a big number. Up to 90 percent. That is how many women with endometriosis report gastrointestinal symptoms.
That number is probably about right. It comes from a summary of the research by a working group at the Cleveland Clinic, though there as a citation in the introduction, not as their own survey. So I name it for what it is: an order of magnitude, not a measurement.
A team around Madison Simons at the Cleveland Clinic examined how heavily women with endometriosis use the healthcare system and which upper gastrointestinal symptoms stand out.
The paper summarises the state of things with numbers: endometriosis affects 10 to 15 percent of women, up to 90 percent report gastrointestinal symptoms, IBS risk is three to five times higher, with IBS rates up to 52 percent. And women with both diagnoses had lower pain thresholds and more painful cycles than women with only one.
For you that means: when both come together, the pain does not simply add up. It amplifies. That explains why standard measures against IBS often fall short in this group.
Simons M, Cline M, Gubbels A et al. Clin Gastroenterol Hepatol. 2024;22(10):2143-2146.e1. PMID: 38513981 · DOI: 10.1016/j.cgh.2024.03.005 [Review, cohort, retrospective]Pooled data are more robust than a single number. There are two such sets.
Francesca Chiaffarino and colleagues pooled eleven studies, among them four cohorts and four case control studies.
Women with endometriosis met the IBS criteria with an odds ratio of 3.26 more often than women without, with a confidence interval of 1.97 to 5.39 and without meaningful scatter between studies. For an IBS diagnosis already in the history, the odds ratio was 3.10.
For you that means: the co-occurrence is not a coincidence of individual practices. The authors name the consequence themselves, namely delayed diagnoses, unsuitable treatments and unnecessary tests.
Chiaffarino F, Cipriani S, Ricci E et al. Arch Gynecol Obstet. 2021;303(1):17-25. PMID: 32949284 · DOI: 10.1007/s00404-020-05797-8 [Meta-analysis, k=11]Khadija Saidi, Shantanu Sharma and Bodil Ohlsson filtered more strictly: endometriosis had to be surgically confirmed, symptoms recorded in a structured way, IBS diagnosed by the Rome criteria. Of 254 publications, 13 remained, and four entered the calculation.
The pooled risk measure was 2.39, with an interval of 1.83 to 3.11. And then the authors write something you rarely read: it is unclear whether a genuine comorbidity is present here or whether the symptoms come from the medication and the cycle phase.
For you that means: the link is stable, the explanation is open. The same group also calls for a check on whether the Rome criteria are even suitable for separating an irritable bowel from other conditions with heightened pain sensitivity in the abdomen.
Saidi K, Sharma S, Ohlsson B. Eur J Obstet Gynecol Reprod Biol. 2020;246:99-105. PMID: 32004880 · DOI: 10.1016/j.ejogrb.2020.01.031 [Meta-analysis, k=4]In the general population it looks weaker
All the numbers so far come from clinics and specialist consultations. That is where the difficult cases land. Sofie Stark Junkka and Bodil Ohlsson therefore analysed a population cohort, the Malmö Offspring Study.
Of 2,200 women with registry data, 72 had endometriosis. The association with IBS was there, but weaker: odds ratio 1.86 instead of above 3. And the more important finding: between women with endometriosis and women with IBS there was no difference in the symptom pattern.
What that means for this article: the symptom list alone does not separate the two diagnoses. That is why the history stands at the centre of this text and not a checklist of complaints.
Junkka SS, Ohlsson B. BMC Gastroenterol. 2023;23(1):228. PMID: 37400789 · DOI: 10.1186/s12876-023-02861-w [Cohort, population based, n=1,915]A raised odds ratio tells you nothing about you. It says something about a group.
Threefold raised sounds dramatic, but it means: most women with IBS do not have endometriosis, and most women with endometriosis do not receive an IBS diagnosis. What these numbers achieve is something else. They justify a question that is otherwise asked too rarely.
You do not need statistics to ask that question. You only need a calendar.
And now you know why I start with numbers and not with reassurance.
The distinguishing feature is called the cycle day
Picture two abdomens. Both hurt, both bloat, both swing between too loose and too firm.
One abdomen responds to food, to deadlines, to lack of sleep. The other responds to that too, but a second rhythm lies over it. A rhythm that does not orient itself to breakfast, but to something that returns every four weeks.
That second rhythm can be seen. But only if somebody asks about it.
Judith Moore and her team analysed 160 women in a specialist IBS clinic in New Zealand, all of whom met the Rome criteria, and split them into two groups: with concurrent endometriosis and without.
36 percent had both. Four features were clearly linked with the concurrent endometriosis: pain during sex, referred pain in the back or leg, bowel symptoms intensified by menstruation, and endometriosis in the family.
For you that means: this is the most workable distinguishing list I have found in the literature on this question. And it does not come from gynaecology, it comes from a gastroenterology clinic. Exactly where you have probably already been.
Moore JS, Gibson PR, Perry RE, Burgell RE. Aust N Z J Obstet Gynaecol. 2017;57(2):201-205. PMID: 28303579 · DOI: 10.1111/ajo.12594 [Cohort, retrospective, n=160]This study is retrospective, it comes from a single centre, and whoever lands there is preselected. It proves no cause. It describes a profile.
| What you can observe | Rather unspecific | Rather a pointer to the menstrual cycle |
|---|---|---|
| Abdominal pain | spread across the month, tied to food | intensifies in the days before and during the bleed |
| Bowel movement | changeable, without a recognisable rhythm | diarrhoea or constipation shift with the bleed |
| Pain during a bowel movement | with hard consistency, with a fissure or haemorrhoids | only or clearly stronger during the bleed, technical term dyschezia |
| Bloating | after certain foods, within minutes | builds up over hours, stronger in the second half of the cycle |
| Sexuality | nothing unusual | pain on deep penetration, often cycle dependent |
| Blood in the stool | bright red on wiping, independent of the cycle | only during the bleed, rare and always needing assessment |
| Family | no clustering | mother or sister with endometriosis |
This table is an observation aid for your conversation, not a diagnostic tool. The right hand column summarises what was linked with a concurrent endometriosis in the cited work.
One more connection belongs to the gynaecological side, one that is often looked at separately although it belongs together.
Paul Yong reviewed the literature on deep dyspareunia, that is pain on deep penetration.
He describes how recurring period pain can make the nervous system more sensitive through priming and can pass into chronic pelvic pain. Pain during a bowel movement, pain on passing urine and IBS symptoms hang together through the same mechanism: central sensitization.
For you that means: when three systems are sensitive at the same time, that is neither coincidence nor a sign of imagination. It is a pointer that processing is involved and not only the organ.
Yong PJ. Minerva Obstet Gynecol. 2022;74(3):222-233. PMID: 35107234 · DOI: 10.23736/S2724-606X.22.04974-0 [Review, narrative]In 109 women no link to menstruation was found
Malin Ek and Bodil Ohlsson in Malmö invited all patients of a gynaecology department with confirmed endometriosis and recorded them with a standardised questionnaire. 109 women, plus 65 controls from the general population.
The symptoms were clearly stronger than in the controls: abdominal pain, constipation, bloating, urgency, the feeling of incomplete emptying. But they were not tied to menstruation and not to the location of the lesions. The only exception was more nausea with findings close to the bowel. And only half the women could tell the pain from the endometriosis apart from the pain from the gastrointestinal tract at all.
What that means: a cyclical pattern is a strong pointer when it is there. Its absence rules nothing out. And if you cannot keep the two sources of pain apart, that is not down to you. Visceral pain is blurred, that is its nature.
Ek M, Roth B, Ekström P et al. BMC Womens Health. 2015;15:59. PMID: 26272803 · DOI: 10.1186/s12905-015-0213-2 [Cohort, case cohort, n=174]A cycle diary across two to three cycles
One line per day. Cycle day, pain from 0 to 10, stool form roughly, perceived abdominal girth from 0 to 10, and a field for anything notable. Paper is enough, a notes app is enough too.
Two cycles are the minimum, three are better. Only then can you see whether a pattern repeats or whether it was chance.
I consider the menstrual cycle the most important diagnostic information that regularly goes unrecorded in the IBS clinic. Not out of carelessness. Rather because the Rome criteria do not ask for it, and because nobody asks about something that is not on the form.
You are not an unreliable narrator of your own symptoms. You have only been plotting them against the wrong axis.
As long as you note symptoms against foods, you see food patterns. Plot the same symptoms against the cycle day and a second pattern may become visible. Or not. Either way that is usable information.
And now you know why I ask about the date before I ask about the food.
Endo belly: what happens there over hours
Flat in the morning. Tight by midday. In the evening only the loose trousers fit, and strangers ask when it is due.
This phenomenon has been given a name that comes from the community and not from science: endo belly. For a long time it was only a word in forums. Since 2023 there has been a first summary appraisal, and it comes from Berlin.
Renata Velho, Franziska Werner and Sylvia Mechsner from the endometriosis research centre at the Charité gathered what is known about endo belly: inflammation, hormonal situation, microbiome, diet, overlap with the irritable bowel.
They describe cyclical distension as a specific feature: in the second half of the menstrual cycle it increases up to menstruation. As a mechanism they name a lowered stretch pain threshold of the bowel wall. They call endometriosis the chameleon among gynaecological conditions.
For you that means: the decisive sentence lies in the mechanics. Your abdomen does not suddenly contain more gas. It reports the same filling more loudly.
Velho RV, Werner F, Mechsner S. J Clin Med. 2023;12(22):7176. PMID: 38002788 · DOI: 10.3390/jcm12227176 [Review, narrative]Because that is a narrative review and not a prospective cohort with a cycle diary, I will say it plainly: endo belly is well described and mechanistically plausible. It has not been measured in a controlled study.
Five routes that can overlap
- Inflammation in the abdominal cavity. Endometriosis lesions are active tissue that releases messengers. The peritoneum can respond with an inflammatory answer, and an inflamed peritoneum can respond more sensitively to stretch. Strength of evidence: described in human tissue, mechanistically plausible.
- A lowered stretch threshold. The bowel wall can report filling as pain earlier. That is the same mechanism called visceral hypersensitivity in IBS, and it may explain why the two pictures look so similar. Strength of evidence: described, fits well with IBS research.
- Altered motility. Progesterone can slow smooth muscle, prostaglandins can speed it up. In the second half of the menstrual cycle this balance can shift. Strength of evidence: physiologically established, not measured separately for the endometriosis group.
- Adhesions. Lesions and previous surgery can stick tissue together. A bowel that does not glide freely can stretch unevenly. Strength of evidence: surgical observation, no study with abdominal girth as an endpoint.
- Concurrent bacterial overgrowth. Where more is fermented, more gas can arise. There is a number for this, and that number has a catch. It follows right below.
These five routes do not exclude one another. In many women several run at the same time, and that is one of the reasons why a single measure rarely changes the whole pattern.
Philippe Halfon and colleagues drew 148 women with confirmed endometriosis from a cohort of 1,027 women who had a lactulose breath test and matched each by age with a woman without endometriosis.
91.9 percent of the endometriosis group tested positive on the breath test for bacterial overgrowth or methane overgrowth. In the control group it was 83.1 percent. The difference was statistically meaningful. Constipation was found in 67.8 versus 44.7 percent.
For you that means: the real message is the control rate. If four out of five women without endometriosis also test positive, then in this testing situation the test is barely measuring anything specific. I draw no treatment recommendation from this, but a warning about the number.
Halfon P, Estrade JP, Penaranda G et al. Int J Gynaecol Obstet. 2025;170(1):284-291. PMID: 39959963 · DOI: 10.1002/ijgo.70005 [Cohort, case control, n=296]What SIBO is, how a breath test runs properly and where its limits lie is in SIBO: bacterial overgrowth in the small bowel. The role of methane forming archaea in constipation is in Methanogens, IMO and constipation.
Part of the abdomen can come from the treatment
The same Swedish study that found no link to menstruation contains something else. Women on opioids had stronger bowel symptoms. Women with current or previous use of GnRH analogues had stronger abdominal pain.
That is plausible. Opioids can slow the bowel, and the Rome criteria now even have their own category for it. And GnRH analogues put the body into a state without a cycle, which often relieves pelvic pain and does not automatically mean the same thing for the bowel.
What that does not mean: that you should question your painkillers or your hormonal treatment. None of this is something you change yourself. It only means this point belongs in the conversation if the abdomen has become worse rather than better under treatment.
Why an abdomen distends at all, with all the other causes from swallowed air to carbohydrate handling, is in Bloating: where the air comes from. Here it was only about the share that belongs to endometriosis.
The most common sentence women hear about endo belly is: you have probably put on weight.
A distension that is gone in the morning and there in the evening is not fat tissue. Fat tissue does not disappear overnight. What comes over hours and goes overnight is volume, water and perception. That is not a question of discipline. It is a question of physiology.
Everything written here about endo belly applies to a distension that comes and goes. It builds over hours and is gone again the next morning.
If your abdominal girth is instead increasing persistently and no longer goes back down, if you are full after only a few bites, if the bloating occurs almost daily and stays for weeks, or if it starts newly after the menopause, then this is not an endo belly. Then it belongs in a prompt gynaecological assessment, with the ovaries among the things to look at. These are exactly the signs by which a disease of the ovaries is regularly noticed too late, because it first looks like a bowel problem.
As a rule this turns out to be nothing serious. But it is not something you observe, it is something you have examined. Please take this point more seriously than anything else in this section.
And now you know why you look different in the evening than in the morning, without anything about you having changed.
Why the colonoscopy usually finds nothing
This is the sentence that probably brought you here. The colonoscopy was normal, and you were glad and annoyed at the same time. Glad, because nothing serious was visible. Annoyed, because the problem stayed anyway.
Behind that sits an anatomy that is rarely explained.
The camera looks at the mucosa from the inside. Endometriosis lesions on the bowel, however, come from the outside. They sit first on the outer coat, the serosa, and grow slowly inwards from there. First through the muscle layer, then into the layer beneath it, and only last of all as far as the mucosa. Until then the camera sees a smooth, pink, entirely normal inner wall.
It is like a stain on the outside of a curtain. From the inside you only notice it once it has soaked through.
Marco Milone and his team in Naples spent three years performing colonoscopy first on all women with clinically and radiologically suspected deep pelvic endometriosis and then operating within four weeks. 174 women between 21 and 42 years old.
In 76 women, bowel endometriosis was found at surgery and on histology. Colonoscopy had detected 6 of them. That gives a sensitivity of 7 percent with a specificity of 98 percent. Broken down by depth: where the mucosa was involved, every case was seen, in the layer beneath it 37.5 percent, in the muscle layer not a single one, and with involvement of the outer coat alone 2.6 percent.
For you that means: your normal colonoscopy was not a mistake and was not wasted. It ruled other things out. It was simply never the instrument for finding endometriosis on the bowel.
Milone M, Mollo A, Musella M et al. World J Gastroenterol. 2015;21(16):4997-5001. PMID: 25945014 · DOI: 10.3748/wjg.v21.i16.4997 [Cohort, prospective, n=174]Four depths, four completely different detection rates
Outer coat only
38 of 76 women. The lesion lies on the serosa, the inner side is untouched.
2.6 percent detectedInto the muscle layer
28 of 76 women. The bowel can harden, the mucosa stays smooth.
0 percent detectedUnder the mucosa
8 of 76 women. Now something sometimes bulges, though it is rarely visible.
37.5 percent detectedInto the mucosa
2 of 76 women. Only here does the camera see something, and here it saw everything.
100 percent detectedNumbers from the Naples series. The illustration is schematic and not to scale. It is only meant to show why the same examination ranges from perfect to blind depending on depth.
A normal colonoscopy does not rule out endometriosis on the bowel. It rules other things out, and that is exactly what it is for.
So that no false impression arises, I will say the other half just as clearly. Colonoscopy is not superfluous, and nobody should postpone or cancel a recommended examination because of this article.
It clarifies blood in the stool. It detects polyps that could later develop into something else. It distinguishes an inflammatory bowel disease from a functional disorder. And in Germany it is part of cancer screening. What to expect from it is in Bowel cancer screening and colonoscopy. How to distinguish Crohn's disease and ulcerative colitis is in Crohn's disease and colitis seen integratively.
The authors of the Naples paper draw exactly this line themselves. Their conclusion is not that colonoscopy is poor. It is that it should not be used routinely in the search for bowel endometriosis, because it cannot answer that question.
Normal does not mean nothing is there. Normal means: in the area this method can see, there was nothing.
Every test has a field of view. A negative test is an answer to exactly one question, not to all of them. If you keep that in mind, you lose less time after a normal result, because then you do not wait, you ask the next question.
And now you know why a normal result and a persistent problem do not contradict each other.
How the diagnosis is actually made today
Many women carry an old piece of information around with them. You can only know for sure after a laparoscopy.
That was the state of things for a long time. It is no longer the current state, and this change is the main reason why the waiting years can shorten.
The European society for reproductive medicine and embryology revised its endometriosis guideline in 2022, with 109 recommendations and a literature base up to the end of 2020.
In five topic areas, substantial changes were needed compared with the previous version. The guideline describes its own diagnostic section explicitly as challenging laparoscopy and tissue examination as the gold standard. Diagnosis and the start of treatment may be based on history and imaging.
For you that means: endometriosis no longer has to be proven surgically before treatment may begin. That does not mean nobody is operated on any more. It means nobody waits years for surgery to confirm the name.
Becker CM, Bokor A, Heikinheimo O et al. Hum Reprod Open. 2022;2022(2):hoac009. PMID: 35350465 · DOI: 10.1093/hropen/hoac009 [Guideline] [Consensus Guideline]For care in German speaking countries another guideline is decisive, and it has one detail that counts for this article.
The S2k guideline on the diagnosis and treatment of endometriosis is carried by the professional societies from Germany, Austria and Switzerland and sits under registry number 015/045, in the revised version from April 2025.
This version contains 25 statements and 73 recommendations based on a systematic literature review covering 2019 to 2023. Two points from it belong directly here: transvaginal ultrasound is named as the central diagnostic procedure, and in treatment hormonal therapy comes first, supplemented by surgical and multimodal approaches depending on the symptom picture.
The author panel includes not only gynaecologists but also gastroenterology, visceral surgery, pathology, pain medicine and the patient representations from all three countries. It is a structured consensus, not an evidence graded guideline.
For you that means: if you ask about the structured approach in the consultation, that is the reference point. And the involvement of the bowel specialties shows that the interface was not overlooked but negotiated.
Burghaus S, Schäfer SD, Bär KJ et al. Geburtshilfe Frauenheilkd. 2026;86(2):133-188. PMID: 41684533 · DOI: 10.1055/a-2760-4867 [Guideline] [Consensus Guideline]Four steps, in this order
History taking with reference to the menstrual cycle
The cheapest and most productive step. Bring the cycle diary, name the period pain, name pain during a bowel movement while bleeding, name pain during sex, name the family history.
costs nothingmost often skippedTransvaginal ultrasound by experienced examiners
The first imaging method, not the second. At the junction from rectum to sigmoid it reaches very good values, provided the person examining is looking for it deliberately.
sensitivity 91 percentspecificity 97 percentMRI, if the ultrasound is inconclusive
Not the automatically better test, but the next step with an unclear finding and before planned surgery, because it shows the extent within the pelvis better.
level with ultrasound at the rectosigmoidLaparoscopy in selected cases
No longer a mandatory step to find the name, but used where it serves a therapeutic purpose or where imaging and symptoms do not fit together.
decision at the centreThis order does not replace medical advice. It is meant to show you where in the conversation you can ask, without demanding something that is not provided for.
Stefano Guerriero and colleagues pooled 19 studies with 2,639 patients in which transvaginal ultrasound had searched specifically for deep endometriosis at the junction of rectum and sigmoid before surgery, with the surgical finding as the standard.
Pooled, this gave 91 percent sensitivity and 97 percent specificity. Whether the examination was done with or without bowel preparation or contrast techniques made no statistical difference. The scatter between studies was high, however.
For you that means: this high scatter is the real subclause. The result depends on the person holding the probe, not on the machine.
Guerriero S, Ajossa S, Orozco R et al. Ultrasound Obstet Gynecol. 2016;47(3):281-289. PMID: 26213903 · DOI: 10.1002/uog.15662 [Meta-analysis, k=19]The same working group later pooled only those studies in which the same patients received both methods. Six studies, 424 patients.
At the rectosigmoid both were at 85 percent sensitivity and about 95 percent specificity. At the rectovaginal septum both were clearly weaker, MRI at 66 percent, ultrasound at 59. At the supporting ligaments of the uterus both were around 70 percent.
For you that means: at the most important bowel site, MRI is not better. And at the difficult sites both are weak, which is why a normal image does not rule out endometriosis. That sentence belongs here just as clearly as the sentence about colonoscopy.
Guerriero S, Saba L, Pascual MA et al. Ultrasound Obstet Gynecol. 2018;51(5):586-595. PMID: 29154402 · DOI: 10.1002/uog.18961 [Meta-analysis, k=6]Why experience makes such a difference was written up by an international group of thirty experts in 2016. Their starting point was mundane and consequential at the same time: studies were not comparable because the same structures were named differently. Since then there has been a standardised examination of the anterior and posterior pelvic compartment with fixed terms and measurement points. So the question you can ask in the clinic is not: do you have a good machine. It is: do you look specifically for deep infiltrating endometriosis, and do you do that according to the standardised approach. Guerriero S, Condous G, van den Bosch T et al. Ultrasound Obstet Gynecol. 2016;48(3):318-332. PMID: 27349699 · DOI: 10.1002/uog.15955 [Consensus Guideline]
Three limits you should know
- Superficial lesions on the peritoneum
- They are flat, small and as a rule not visible on ultrasound. They can still cause severe pain.
- The rectovaginal septum
- Here both methods were below 70 percent sensitivity in a direct comparison. An empty finding at this site says little.
- The junction to the small bowel
- Involvement there is rare and was found in an Italian series of 31 women without exception only during surgery. In 94 percent there was simultaneous colorectal endometriosis, so it almost never occurs in isolation.
Source for the last line: Ruffo G, Stepniewska A, Crippa S et al. Surg Endosc. 2011;25(4):1257-1262. PMID: 20848137 · DOI: 10.1007/s00464-010-1354-x [Cohort, prospective series, n=31]
The reflex after an unclear finding is often: I need the stronger machine. So MRI instead of ultrasound.
The data say something else. At the bowel, what matters is not the more expensive method but the question somebody is looking with. A targeted ultrasound by an experienced examiner beats an MRI ordered without a concrete question.
You can bring that question along. That is the part you can influence.
And now you know why the answer can come faster today than it did ten years ago.
Treatment routes and what they do to the gut
Suppose the question has been asked and the answer is yes. Then the next uncertainty arrives: which of this actually changes my abdomen and not only my pelvis?
This question is rarely answered separately, because most studies measure pelvic pain and not bowel symptoms. But there are papers that look precisely at this.
None of what follows is something you change yourself. Do not start, stop or switch a hormonal treatment, do not reduce a painkiller on your own, do not postpone a planned examination. Every adjustment belongs in medical hands. This section exists so that you can ask better questions in the conversation.
Track one: hormonal treatments
The idea behind it is simple. Endometriosis lesions respond to oestrogen. If the cyclical stimulus is dampened, the activity of the lesions may decline, and with it the inflammation attached to it.
Fabio Barra and colleagues in Genoa retrospectively analysed a prospectively maintained database. Included were women with nodules reaching at least into the muscle layer of the rectosigmoid wall, without relevant narrowing, on continuous dienogest.
After one year, period pain, pelvic pain, pain during sex and above all pain during a bowel movement declined clearly. Quality of life rose over two years, measured also on an index built specifically for gastrointestinal quality of life. After that the improvement was maintained.
For you that means: with proven bowel involvement, bowel symptoms may decline under a targeted hormonal treatment. The catch sits in the methods: there was no control group and no randomisation, and the measurement was against each woman's own baseline.
So that you can place the substance: dienogest is a prescription only progestogen approved for the treatment of endometriosis. It is not a contraceptive and should not be relied on as one. It must not be taken in pregnancy. Restrictions apply with current or previous thrombosis, with severe liver disease and with hormone dependent tumours. Commonly described are breakthrough bleeding, headache, breast tenderness and mood changes. Whether it is an option for you is decided by the doctor treating you. I deliberately give no dose here.
Barra F, Scala C, Leone Roberti Maggiore U, Ferrero S. J Clin Med. 2020;9(1):154. PMID: 31935969 · DOI: 10.3390/jcm9010154 [Retrospective, without control arm]In a Swedish cohort nothing changed at the bowel
The same study from Malmö that found no link to menstruation had a prospective part. Women who newly started a combined pill or a progestogen were followed up.
On bowel symptoms this start had no measurable effect. And women with current or previous use of GnRH analogues had stronger abdominal pain.
What that means: in the pelvis a hormonal treatment can often bring relief. At the bowel the data are inconsistent. Both papers therefore stand side by side in this text, and neither of them settles the question.
Honesty belongs to the side effects. Irregular bleeding is common on continuous progestogens and usually decreases over time. Mood changes, loss of libido and bone metabolism are topics that weigh differently depending on the preparation and the duration. With GnRH analogues, menopausal symptoms are added, and above all bone density can decrease. That is precisely why they are usually used only for a limited time and in combination with so called add back treatment, which gives part of the hormones back. If such a treatment is suggested to you, the question about duration, about add back and about monitoring of bone density is a good question. GnRH analogues are prescription only medicines as well and must not be used in pregnancy or while breastfeeding. All of this belongs in the informed consent conversation, not in a blog article with the character of a recommendation. And it is explicitly not a reason to end or alter an ongoing treatment on your own. That too belongs in medical hands.
Track two: surgery in the deep infiltrating form
When a nodule infiltrates the bowel wall, causes symptoms and imaging and clinical picture fit together, surgery is discussed. Two techniques are available: gentle removal from the outside, or removal of a whole bowel segment with a subsequent join.
Which technique comes into question depends among other things on how long the nodule is and how much it narrows the bowel. A French series of 27 women describes computed tomography based virtual colonoscopy for this, which allows the length and diameter of the narrowing to be measured before surgery. Vassilieff M, Suaud O, Collet-Savoye C et al. Gynecol Obstet Fertil. 2011;39(6):339-345. PMID: 21596608 · DOI: 10.1016/j.gyobfe.2011.04.004 [Cohort, prospective series, n=27]
Horace Roman and colleagues randomised 60 patients with deep endometriosis of the rectum at three French university hospitals: conservative technique versus removal of a bowel segment.
After 24 months about half of each group had at least one functional problem, 48.1 versus 39.4 percent, without a meaningful difference in quality of life scores. What did show up was a clearly higher risk of a narrowing of the bowel after segmental resection. The authors themselves call their study underpowered for the primary endpoint.
For you that means: the widespread assumption that the more conservative technique is automatically also functionally better could not be confirmed here. What was confirmed is the difference in stenosis risk.
Roman H, Bubenheim M, Huet E et al. Hum Reprod. 2018;33(1):47-57. PMID: 29194531 · DOI: 10.1093/humrep/dex336 [RCT, n=60]Sophia Braund and her team analysed 431 consecutive operations on the rectosigmoid, 165 with excision of a disc from the bowel wall, 266 with removal of a segment.
23 women developed a narrowing after segmental resection, that is 8.6 percent. After disc excision, not a single one. The narrowing could be treated by dilation in 87 percent of cases, in four women a further operation was needed, and in one the dilation caused an injury with a subsequent fistula.
For you that means: this number does not speak against surgery. It speaks for the choice of technique and for the experience of the centre where the operation takes place.
Braund S, Hennetier C, Klapczynski C et al. J Minim Invasive Gynecol. 2021;28(1):50-56. PMID: 32360656 · DOI: 10.1016/j.jmig.2020.04.034 [Cohort, retrospective, n=431]One point that matters to many women concerns fertility. In the extended follow up of the same French group, 36 of 55 women wanted to become pregnant after surgery. 29 of them did, that is 81 percent, 17 of those naturally. Among the women who had tried unsuccessfully for over a year beforehand, the rate was 74 percent. The median age was 28 years, a single very experienced surgeon operated, and only large infiltrations were included. This cannot be transferred to small nodules. Roman H, Chanavaz-Lacheray I, Ballester M et al. Hum Reprod. 2018;33(9):1669-1676. PMID: 30052994 · DOI: 10.1093/humrep/dey146 [RCT, follow up, n=36]
Nowhere do I write anything against an operation that is medically justified. If a nodule narrows the bowel, waiting is not a harmless option. What I do write is something else: this decision belongs at a centre with experience, with a conversation about both techniques and about the numbers above. It does not belong in a blog article and not in a forum.
Track three: the pain itself as a treatment target
Luisa Masciullo and colleagues in Rome reviewed the literature from 1995 to 2020 on how endometriosis pain arises.
A link between pain intensity and the stage of the disease rarely exists. Clear, by contrast, is the link with deep lesions. Involved in the generation of pain are central sensitization, the activation of pain conducting pathways, the immune system and the stress axis.
For you that means: few visible lesions can cause severe pain, large findings can stay quiet. The picture on the scan says little about the experience. That takes the weight off every woman who has been told it surely cannot be that bad.
Masciullo L, Viscardi MF, Piacenti I et al. Minerva Obstet Gynecol. 2021;73(5):511-522. PMID: 33904687 · DOI: 10.23736/S2724-606X.21.04779-1 [Systematic Review]If central sensitization is involved, then methods that work on processing rather than on the organ become interesting. How the vagus nerve is involved and which approaches have been studied is in The gut brain axis and vagus stimulation. The best studied psychological method for bowel symptoms is in Gut directed hypnotherapy for IBS. Neither replaces gynaecological treatment. They can accompany it.
Many women experience the choice as an either or. Hormones or surgery. Medicine or lifestyle.
In practice it runs differently. The three tracks lie side by side and are mixed, and the mix changes with the phase of life, with the wish for children and with whatever is most burdensome right now.
Your task is not to choose the right track. Your task is to be able to name what restricts you most. The order follows from that.
And now you know why the question about the abdomen has to be asked explicitly in the endometriosis clinic.
Nutrition: what is evidenced and what is not
Search for endometriosis and nutrition and you get a great many promises and very few numbers. So I sort this into three tiers, and the lowest tier is the most honest one.
Tier one: FODMAP, the only measure with data of its own
The same New Zealand analysis that produced the four distinguishing features also recorded the response to a reduction of fermentable carbohydrates. All women received the same first line treatment.
After four weeks, 72 percent of the women with endometriosis reported an improvement in bowel symptoms of more than half, compared with 49 percent of the women without known endometriosis. The odds ratio was 3.11 with an interval of 1.5 to 6.2.
For you that means: the response rate in this group was higher, not lower. That contradicts the widespread assumption that with endometriosis nutrition is pointless anyway because the cause lies elsewhere.
Moore JS, Gibson PR, Perry RE, Burgell RE. Aust N Z J Obstet Gynaecol. 2017;57(2):201-205. PMID: 28303579 · DOI: 10.1111/ajo.12594 [Cohort, retrospective, n=160]Rafał Watrowski and an international team systematically searched in 2026 for all clinical studies on FODMAP reduction in endometriosis, prospectively registered and following current standards.
They found five reports: one randomised study in a crossover design with controlled catering, two prospective studies without randomisation, one retrospective audit and one case report. The randomised study showed a better response over 28 days than a nutrient matched comparison diet. Because of the strong differences between the studies, a pooled analysis was not possible.
For you that means: the authors call the approach potentially useful for selected patients, under the supervision of a dietitian, and explicitly not as a permanent state. Five studies with a single randomisation are a beginning, not a proof.
Watrowski R, Kostov S, Schäfer SD et al. Nutrients. 2026;18(13):2164. PMID: 42451164 · DOI: 10.3390/nu18132164 [Systematic Review, k=5]How a FODMAP reduction runs properly in three phases, with elimination, reintroduction and a long term diet, is in Using FODMAP properly. The most important sentence from there belongs here too: the elimination phase is not a goal, it is a test. Anyone who restricts strictly for good loses variety and feeds their own bacteria less well. And one restriction that matters in daily life: in pregnancy, while breastfeeding and with an eating disorder in the history, a FODMAP elimination does not belong in self management but in the care of a dietitian or in medical hands.
Tier two: mechanistically plausible, human data thin
This is where omega-3 fatty acids and fat quality in general land. The reasoning behind it is understandable: arachidonic acid gives rise to inflammation promoting messengers, the long chain omega-3 fatty acids rather to inflammation resolving ones. Endometriosis is an inflammatory condition. So the ratio ought to have an effect.
A Polish review from 2023 reports the following observation from the existing literature: a higher intake of saturated fats, especially palmitic acid, and of trans fats was linked with a higher risk in individual studies, monounsaturated fats and omega-3 with a lower one. That is an observation from mostly retrospective surveys, not a recommendation and not a claim of effect. The authors write themselves that the studies are contradictory because of sample size, design and methods. Marcinkowska A, Górnicka M. Life (Basel). 2023;13(3):654. PMID: 36983810 · DOI: 10.3390/life13030654 [Review, narrative]
Fabio Parazzini and colleagues in Milan brought together, in a literature review with a comprehensive database search, whatever exists on the link between diet and endometriosis risk.
Eleven studies, ten of them case control studies and a single cohort. In seven of them, diet was recorded by food frequency questionnaire. Women with endometriosis appeared to consume less vegetables and less omega-3 and more red meat, coffee and trans fats. These findings could not be reproduced consistently, however.
For you that means: the authors call the evidence inconclusive. Diet may influence symptoms. On current data it does not steer the disease. That is not a rejection of good food, it is a correction of expectations.
Parazzini F, Viganò P, Candiani M, Fedele L. Reprod Biomed Online. 2013;26(4):323-336. PMID: 23419794 · DOI: 10.1016/j.rbmo.2012.12.011 [Literature review, k=11]Tier three: popular, but not evidenced
Three approaches I do not call evidenced in this context
- Gluten free without coeliac disease. There are women who report feeling better on it. Controlled data specifically for endometriosis do not exist. Important, and this is the point with the greatest practical consequence in this field: if coeliac disease is a possibility, a gluten free diet before the diagnostic work up can make the diagnosis impossible. Get tested first, then leave things out. More on that in Recognising coeliac disease.
- Complete avoidance of dairy. The data base for a general recommendation is missing. If lactose intolerance is present, that is a different question, and it is covered in Lactose, fructose, sorbitol.
- Anti candida concepts in endometriosis. No robust human data exist for this connection. What has actually been studied about candida in the gut is covered elsewhere in the cluster.
And the microbiome?
Tamy Colonetti and colleagues in Brazil searched systematically for observational studies comparing the gut and vaginal microbiome of women with and without endometriosis.
Sixteen studies were found. For diversity in the gut microbiome, pooling four studies with 357 participants gave no meaningful difference. For the vaginal microbiome likewise not. Individual studies showed abnormalities, the pooled analysis did not.
For you that means: the widespread story of the endometriosis microbiome does not carry at present. A stool test does not answer the question of whether endometriosis is present. What a stool test can and cannot do is in Stool testing, PCR and dysbiosis diagnostics.
Colonetti T, Saggioratto MC, Grande AJ et al. Biomed Res Int. 2023;2023:2675966. PMID: 38601772 · DOI: 10.1155/2023/2675966 [Meta-analysis, k=16]Where the menstrual cycle, blood sugar and the hormonal situation interact and what nutrition can change there is in Nutrition, hormones, blood sugar and cortisol. That too is no substitute for the gynaecological work up, but a second dial to turn.
The quiet expectation behind every change of diet is: if I do it right, it will go away.
With an oestrogen dependent condition with lesions in the abdominal cavity, that is the wrong yardstick. The realistic expectation is: less bloating, less pain during a bowel movement, more predictable days in the month. That sounds smaller. In everyday life it is a great deal.
And whoever applies the smaller yardstick stops sooner trying to leave out yet one more thing.
And now you know what food can realistically change with this topic and what it cannot.
The next step, concretely
If you have read this far, you have probably already heard plenty of advice. So I am keeping this part short and limiting it to what you can set in motion yourself.
Three steps, in this order
- A cycle diary across two to three cycles. One line per day: cycle day, pain from 0 to 10, stool form, perceived abdominal girth, anything notable. Without this data the conversation is a memory exercise, and memory averages.
- A gynaecology appointment with a concrete question. Not: my stomach hurts. Rather: my bowel symptoms shift with my menstrual cycle, I have pain during a bowel movement while bleeding, and I want to know whether deep infiltrating endometriosis is a possibility and whether the ultrasound can look for it specifically.
- Ask the centre question. If the answer stays unclear or the findings do not match your symptoms, the next question is where near you deep infiltrating endometriosis is looked for specifically. On the available data, the experience of the person examining seems to matter more here than the equipment.
And if all these routes come up empty: then an irritable bowel is a very good and very treatable explanation. The difference is only that you then know why, instead of suspecting it. How things continue from there is in the overall concept under Gut reset.
I consider the menstrual cycle the most important diagnostic information that regularly goes unrecorded in the IBS clinic. And a cycle diary the cheapest tool there is for it.
Shukri JarmoukliOne last thing, because otherwise it gets lost. If you have lived for years with symptoms nobody could explain, then at some point you probably started questioning yourself. Whether you are exaggerating. Whether you are too sensitive. Whether it is in your head after all.
You can set that question aside. A diagnostic delay of nearly seven years on average is a feature of the system and not a feature of your perception. And severe period pain that limits your daily life was never a sign of weakness. It is a reason to look.
Frequently asked questions
How can I tell whether endometriosis is sitting behind my IBS diagnosis?
Four features were significantly linked with concurrent endometriosis in a New Zealand IBS clinic: pain during sex, referred pain in the back or leg, bowel symptoms that intensify with menstruation, and endometriosis in the family. Pain during a bowel movement while bleeding belongs alongside them. These features prove nothing, but they are the reason to raise the question in gynaecology.
Can endometriosis cause diarrhoea and constipation in alternation?
Yes, this pattern is described. In a case cohort of 109 women with confirmed endometriosis, constipation, bloating, urgency and the feeling of incomplete emptying were clearly more common than in controls, although without a link to menstruation. Some women do report cyclical diarrhoea around the bleed, and the data on that are thin. The alternation on its own does not separate endometriosis from IBS, because it occurs in both.
What exactly is an endo belly and how long does it last?
Endo belly describes a distension of the abdomen that builds over hours, is stronger in the evening than in the morning and increases in the second half of the menstrual cycle. A team at the Charité in Berlin brought the phenomenon together in a first summary in 2023. The mechanism they describe is a lowered stretch pain threshold of the bowel wall. So the abdomen is not necessarily fuller, it responds more sensitively to the same filling. The duration ranges from hours to several days.
Why does my abdomen bloat especially before my period?
In the second half of the menstrual cycle, bowel motility, fluid balance and pain threshold can shift at the same time. With endometriosis an inflammatory response in the abdominal cavity can be added, and in some women adhesions as well. A narrative review from the Charité describes exactly this course with an increase up to menstruation. That is described, not proven in a prospective cohort with a cycle diary.
My colonoscopy was normal. Does that rule out endometriosis?
No. A prospective study in 174 women found bowel endometriosis at surgery in 76 of them, and colonoscopy had detected 6 of those. That corresponds to a sensitivity of 7 percent. The reason is anatomical: the lesions sit on the outside of the bowel wall and grow inwards, so the mucosa stays uninvolved for a long time. Colonoscopy rules out other causes, and that is what it is for. A recommended colonoscopy should therefore not be skipped.
What is deep infiltrating endometriosis of the bowel and how common is it?
Deep infiltrating endometriosis means lesions reaching more than about 5 millimetres beneath the peritoneum. On the bowel this usually involves the rectum and sigmoid. In a series of 174 women with deep pelvic endometriosis, 43.6 percent had bowel involvement, half of them only on the outer coat. Involvement at the junction to the small bowel is rare and almost never occurs in isolation.
Is blood in the stool during the period always endometriosis?
No, and that is exactly why this sign is so delicate. Blood in the stool always belongs in medical assessment, whatever the cycle day. A fissure, haemorrhoids, inflammatory bowel disease, a polyp or a tumour can produce the same bleeding. A cyclical pattern is an additional pointer for gynaecology, it does not replace the assessment of the other causes.
How is bowel endometriosis investigated today, if not by colonoscopy?
First through the history with reference to the menstrual cycle, then through transvaginal ultrasound performed by experienced examiners. A meta-analysis with 2,639 patients found a pooled sensitivity of 91 percent and a specificity of 97 percent at the rectosigmoid, although with very high variation between the individual studies. These figures apply to experienced examiners at this one site, not to every ultrasound. In a direct comparison with MRI there was no difference at the rectosigmoid. Important: a normal image does not rule endometriosis out either, especially with superficial lesions on the peritoneum.
Do I have to be operated on to get the diagnosis?
Not necessarily. The 2022 ESHRE guideline explicitly challenges laparoscopy and histology as the gold standard and states that diagnosis and the start of treatment may be based on history and imaging. That does not mean nobody is operated on any more. It means nobody has to wait years for surgery to confirm the name.
How long does it take on average to reach a diagnosis of endometriosis?
In a study across 16 centres in ten countries with 1,418 women, 6.7 years lay between the first symptom and the surgical diagnosis. In predominantly publicly funded systems it was 8.3 years, elsewhere 5.5. In studies the average delay is therefore around seven to ten years, depending on country and survey. The delay arose predominantly in primary care, not in the mind of individual doctors.
Does a low FODMAP diet do anything in endometriosis, or only in IBS?
In a New Zealand analysis, after four weeks 72 percent of women with endometriosis reported an improvement in bowel symptoms of more than 50 percent, compared with 49 percent without known endometriosis. A systematic review from 2026 found five clinical studies in total, only one of them randomised. The authors call the approach potentially useful for selected patients under professional supervision, not as a permanent state.
Do omega-3 or an anti-inflammatory diet do anything in endometriosis?
Mechanistically that is plausible, the human data are thin. A literature review from 2013 screened eleven studies, ten of them case control studies, and calls the evidence explicitly inconclusive. A review from 2023 describes associations with fat quality and calls the studies contradictory. Diet may influence symptoms. On current data it does not steer the disease.
Can hormonal treatment improve or worsen my bowel symptoms?
Both are described. On continuous dienogest, pain during a bowel movement and bowel symptoms decreased over years in women with rectosigmoid endometriosis, measured on a gastrointestinal quality of life index as well, although without a control group. In a Swedish cohort, starting a pill or a progestogen had no prospective effect on bowel symptoms, and abdominal pain was stronger under GnRH analogues. Dienogest and GnRH analogues are prescription only medicines and have contraindications of their own, pregnancy among them. None of this is something you change yourself, every adjustment belongs in medical hands.
When does bowel surgery become a topic and what are the risks?
It becomes a topic in deep infiltrating endometriosis of the rectosigmoid with relevant symptoms or a threatened narrowing. A randomised trial with 60 patients could not demonstrate a functional advantage of the more conservative technique over segmental resection after 24 months, but was too small for that endpoint according to the authors. Clearer was the higher stenosis risk after resection. A series of 431 women found 8.6 percent stenoses after segmental resection and none after disc excision, although with unevenly distributed baseline findings. These numbers belong in the informed consent conversation at an experienced centre.
Can I have endometriosis even though my period pain is mild?
Yes. A systematic review describes that pain intensity and extent of disease rarely match, while the association with deep lesions is clear. Small findings can cause severe pain, large ones can stay quiet. The reverse holds just as much: severe period pain that limits your daily life is not normal and belongs in medical assessment, whatever an earlier finding looked like.
Where this topic connects to the rest of the body
An abdomen that follows the menstrual cycle hangs on more than one organ. On the hormonal situation, on iron balance with heavy bleeding, on pain processing and on what the body makes of food.
Endometriosis: causes
The condition itself, with oestrogen, the immune system and models of its origin
Understanding PMS
What happens physiologically in the second half of the cycle and what follows from it
Hormonal imbalance
When several axes fall out of rhythm at the same time
Cycle based nutrition
Four phases, four sets of needs, and how much of that is evidenced
Iron deficiency with heavy bleeding
Why fatigue in endometriosis often has a second cause
Histamine and DAO
Another picture that can fluctuate cyclically and is often confused with this one
Scientific sources
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- Burghaus S, Schäfer SD, Bär KJ et al. Diagnosis and Therapy of Endometriosis. Guideline of the DGGG, OEGGG and SGGG, S2k Level, AWMF Registry Number 015/045, April 2025. Geburtshilfe Frauenheilkd. 2026;86(2):133-188. PMID: 41684533 · DOI: 10.1055/a-2760-4867 [Guideline] [Consensus Guideline]
- Mearin F, Lacy BE, Chang L et al. Bowel Disorders. Gastroenterology. 2016;150(6):1393-1407.e5. PMID: 27144627 · DOI: 10.1053/j.gastro.2016.02.031 [Guideline] [Consensus Guideline]
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- Moore JS, Gibson PR, Perry RE, Burgell RE. Endometriosis in patients with irritable bowel syndrome: Specific symptomatic and demographic profile, and response to the low FODMAP diet. Aust N Z J Obstet Gynaecol. 2017;57(2):201-205. PMID: 28303579 · DOI: 10.1111/ajo.12594 [Cohort, retrospective, n=160]
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- Zondervan KT, Becker CM, Missmer SA. Endometriosis. N Engl J Med. 2020;382(13):1244-1256. PMID: 32212520 · DOI: 10.1056/NEJMra1810764 [Review]
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- Guerriero S, Saba L, Pascual MA et al. Transvaginal ultrasound vs magnetic resonance imaging for diagnosing deep infiltrating endometriosis: systematic review and meta-analysis. Ultrasound Obstet Gynecol. 2018;51(5):586-595. PMID: 29154402 · DOI: 10.1002/uog.18961 [Meta-analysis, k=6]
- Vassilieff M, Suaud O, Collet-Savoye C et al. Computed tomography-based virtual colonoscopy: an examination useful for the choice of the surgical management of colorectal endometriosis. Original article in French. Gynecol Obstet Fertil. 2011;39(6):339-345. PMID: 21596608 · DOI: 10.1016/j.gyobfe.2011.04.004 [Cohort, prospective series, n=27]
- Barra F, Scala C, Leone Roberti Maggiore U, Ferrero S. Long-Term Administration of Dienogest for the Treatment of Pain and Intestinal Symptoms in Patients with Rectosigmoid Endometriosis. J Clin Med. 2020;9(1):154. PMID: 31935969 · DOI: 10.3390/jcm9010154 [Retrospective, without control arm]
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- Endo belly is described, not measured. The main source for it is a narrative review without a systematic search. There is no prospective cohort that plotted abdominal girth against cycle day. The text therefore says described throughout, and not evidenced.
- The cyclical binding of bowel symptoms is contradictory. One paper found it clearly, another found it not at all in 109 patients. Both stand in the same section. Cyclical patterns are a pointer, their absence rules nothing out.
- The high association figures come from specialist clinics. In a population cohort the odds ratio was 1.86 instead of above 3, and the symptom pattern did not separate the two diagnoses. Anyone reading only the clinic numbers overestimates how sharply they discriminate.
- The 90 percent figure is a citation, not an own measurement. It appears in the introduction of a healthcare utilisation paper. The text therefore names it as an order of magnitude with a reference and not as a result.
- The colonoscopy figure comes from a single prospective series of 174 women from one centre, all with a pre-existing suspicion of deep endometriosis. The direction is unambiguous and anatomically well explainable. A second series of this size for confirmation is missing.
- The ultrasound figures have very high scatter between studies. The meta-analysis states this explicitly. The 91 percent applies to experienced examiners at one particular location, not to every ultrasound.
- There is no control arm for the effect of dienogest on bowel symptoms. Measurement was against each woman's own baseline. Part of the improvement may be the passage of time and expectation.
- The only randomisation on surgical technique has 60 participants and is described by the authors themselves as too small for the primary endpoint. The stenosis figures come from a retrospective series with unequally distributed baseline findings.
- The fertility figures come from a single centre with a single surgeon, median age 28 years and only large infiltrations. They cannot be transferred to other situations.
- Five studies exist on FODMAP reduction in endometriosis with a single randomisation. The headline figure of 72 versus 49 percent comes from a retrospective analysis in a specialist clinic.
- On omega-3 and fat quality there are predominantly case control studies with questionnaire based data collection. The authors call the evidence inconclusive and contradictory respectively. The text therefore names no dose and makes no promise.
- The microbiome meta-analysis appeared in a journal that has been criticised over quality problems. It is cited here solely for the null statement, that is for the fact that no difference was found, and not for a positive claim.
- What deliberately does not appear here. No dosage recommendation, no treatment protocol and no advice to alter, reduce or stop an existing medication. Every adjustment belongs under medical supervision. From no section does it follow that a recommended colonoscopy, endoscopy or laboratory work up should be skipped, postponed or replaced, and from no section does an argument follow against a medically justified operation. What I describe from my own consultations is marked as observation and is not a study result.