Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Endometriosis symptoms and clinical diagnosis
Obstetrics and gynaecology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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Escalate acute organ-threatening features
Endometriosis usually follows a chronic course, but severe sudden pain, peritonism, vomiting, heavy bleeding, pregnancy-related pain, bowel obstruction, visible haematuria with flank pain or renal impairment can signal an acute complication or a different emergency.
Action: Assess observations and pregnancy status, investigate haemorrhage, torsion, ectopic pregnancy, infection, bowel obstruction and urinary obstruction according to the presentation, and involve acute gynaecology, surgery or urology rather than assuming a routine endometriosis flare.
Overview
Recognise the varied symptom patterns of endometriosis, begin treatment and investigation in parallel, and refer appropriately without allowing normal examination or imaging to end the diagnostic pathway.
Endometriosis is a chronic inflammatory condition in which tissue resembling endometrium is present outside the uterine cavity. Common sites include pelvic peritoneum, ovaries, uterosacral ligaments and the rectovaginal compartment; bowel, bladder, ureters, diaphragm and surgical scars can also be involved. An ovarian endometrioma is a cyst formed by ovarian endometriotic disease. Deep endometriosis infiltrates beneath the peritoneal surface and can distort or invade bowel, bladder, ureter and supporting structures.
No single origin explains every phenotype. Retrograde menstruation with implantation, coelomic metaplasia, lymphatic or haematogenous spread, altered immune clearance and genetic susceptibility may contribute. Oestrogen-responsive lesions generate inflammatory mediators, bleeding and fibrosis. Repeated inflammation can tether organs and produce adhesions; persistent nociceptive input can sensitise peripheral nerves, the pelvic floor and central pain pathways. Consequently, a small superficial burden can cause severe pain and extensive deep disease can occasionally be minimally symptomatic.
Practice
Two practice questions
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Obstetrics and gynaecologyOriginal SBA
Normal examination in suspected disease
A 19-year-old has disabling dysmenorrhoea, deep dyspareunia and cyclical painful defecation. Abdominal and pelvic examinations are normal. Which investigation does NICE recommend offering at this stage?
Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.
NICE's symptom trigger is deliberately broad. Consider endometriosis in anyone, including adolescents, with chronic pelvic pain; dysmenorrhoea that affects daily activity or quality of life; deep dyspareunia; period-related painful defecation or other cyclical gastrointestinal symptoms; period-related dysuria or haematuria; or infertility together with such symptoms. Ask directly about school or work absence, sleep, fatigue, analgesic use, intimacy, bowel and bladder timing, fertility plans and family history. A symptom diary can show cyclicity but is not a diagnostic requirement.
Examination is guided by consent, age, symptoms and acceptability. Abdominal examination may identify tenderness, scars or a mass. Pelvic examination can identify a fixed or retroverted tender uterus, endometriotic nodularity, reduced organ mobility, adnexal masses or visible vaginal disease, but may be entirely normal. Offer an abdominal examination if internal examination is declined or unsuitable. Never use the inability to tolerate an examination as evidence against disease; adapt the next step and consider trauma-informed support.
The 2024 NICE diagnostic update places transvaginal ultrasound early for all suspected cases, including normal examination, to find endometriomas, deep disease and competing pathology and to guide referral. A general scan should not be expected to map every deep lesion, so specialist transvaginal ultrasound or pelvic MRI is considered when deep endometriosis is suspected, with expert planning and interpretation. A transabdominal scan is an alternative when transvaginal imaging is unsuitable, but its limits should be explained.
Normal imaging does not exclude endometriosis. Consider diagnostic laparoscopy when suspicion persists even after normal ultrasound or MRI, after discussing whether diagnosis, possible simultaneous treatment and fertility priorities justify operative risks. Laparoscopy should inspect the pelvis systematically, record findings with images and biopsy suspicious lesions when appropriate. Histology supports diagnosis and excludes mimics, but a negative biopsy does not always exclude endometriosis. After a well-performed normal laparoscopy, reconsider other pain mechanisms while maintaining review for clinical change.
Clinical diagnosis is an active working diagnosis, not careless labelling. NICE supports investigation and referral alongside initial treatment, so symptoms can be addressed while the pathway develops. Refer to general gynaecology when initial treatment fails, is not tolerated or is contraindicated, when symptoms recur or materially affect daily living, or when pelvic signs are present. Refer endometrioma, deep or extra-pelvic disease to a specialist centre; include fertility expertise when conception is a priority.
Key points
Suspect endometriosis with chronic pelvic pain, dysmenorrhoea affecting activities and quality of life, deep pain during or after sex, cyclical bowel or urinary symptoms, or infertility accompanied by one or more of these features.
The disease is defined by endometrium-like tissue outside the uterus; symptoms arise from inflammation, fibrosis, adhesions, ovarian endometriomas and deep infiltration, while pain severity correlates poorly with visible extent.
Take symptoms in adolescents seriously, including school absence and pain resistant to simple treatment; people aged 17 and under with suspected or confirmed disease need a paediatric and adolescent gynaecology or specialist endometriosis service.
NICE recommends transvaginal ultrasound for everyone with suspected endometriosis even when abdominal and pelvic examinations are normal; use transabdominal ultrasound when transvaginal scanning is declined or unsuitable.
A normal examination, ultrasound or MRI does not exclude endometriosis, particularly superficial peritoneal disease; continue referral and treatment decisions according to symptoms and impact.
Do not use serum CA125 to diagnose endometriosis: it lacks the accuracy to confirm or exclude disease and may be raised in several benign or malignant conditions.
Aetiology
01
Multifactorial origin
Retrograde menstruation, metaplasia, altered immune clearance, genetic susceptibility and lymphatic or haematogenous spread may contribute; no single theory explains all pelvic and extra-pelvic disease.
02
Hormonal and inflammatory dependence
Ectopic endometrium-like tissue responds to ovarian hormones and generates inflammatory, angiogenic and fibrotic signalling, although lesions vary in hormone sensitivity and activity.
03
Risk and association
Family history and reproductive factors influence probability, but the absence of any recognised risk factor does not make a characteristic symptom pattern unimportant.
Pathophysiology
1
Cyclical lesion activity
Hormone-responsive implants proliferate and may bleed, provoking local inflammation and explaining dysmenorrhoea and period-related bowel, bladder or scar symptoms.
2
Fibrosis and distortion
Repeated tissue injury and repair produces fibrosis, adhesions, endometriomas and reduced organ mobility, contributing deep dyspareunia, obstruction and impaired tubo-ovarian anatomy.
3
Neuroangiogenesis and sensitisation
Lesions recruit vessels and nerve fibres while persistent nociceptive input lowers peripheral and central pain thresholds, allowing symptoms to outlast or exceed visible lesion burden.
4
Organ-specific injury
Deep plaques can narrow bowel or ureter, infiltrate bladder or involve ovarian cortex; mechanical effects and treatment can both threaten function and fertility.
Clinical features and red flags
Painful period phenotype
Dysmenorrhoea that limits school, work, sleep or ordinary activity is clinically important even when it began in adolescence and routine ultrasound is normal.
Deep disease phenotype
Deep dyspareunia, painful defecation, cyclical rectal bleeding, dysuria, haematuria or flank symptoms raise concern for rectovaginal, bowel, bladder or ureteric involvement.
Ovarian phenotype
An endometrioma may cause chronic or acute unilateral pain, pelvic fullness or infertility and carries implications for specialist referral, torsion, rupture and ovarian reserve.
Extra-pelvic phenotype
Cyclical scar swelling or pain, chest symptoms or pain outside the pelvis can reflect extra-pelvic disease and warrants specialist assessment rather than dismissal as atypical.
Fertility phenotype
Subfertility may accompany adhesions, ovarian disease or inflammatory dysfunction; fertility priorities change the balance between suppression, surgery and assisted reproduction.
Red flags requiring action
Syncope, haemodynamic change, guarding, rebound tenderness or abrupt maximal pain requires urgent assessment for ectopic pregnancy, torsion, cyst rupture, haemorrhage or another surgical cause.
Cyclical haematuria, flank pain, hydronephrosis or falling renal function may indicate ureteric or urinary-tract endometriosis and needs specialist assessment before irreversible renal damage occurs.
Investigations
01Transvaginal pelvic ultrasoundFirst step
Why
Identify endometriomas and deep endometriosis, assess bowel, bladder or ureteric clues, find alternative pathology and guide the referral destination.
Interpretation and limitations
Offer despite a normal examination. A positive scan can establish actionable disease, but a normal scan does not exclude superficial endometriosis and must not terminate the pathway.
02Transabdominal pelvic ultrasound
Why
Provide pelvic imaging when transvaginal scanning is declined, unsuitable or not acceptable to the person.
Interpretation and limitations
It can identify larger masses and some uterine or ovarian disease but has lower resolution for several endometriosis sites; explain why further specialist imaging may still be needed.
03Specialist ultrasound or pelvic MRI
Why
Diagnose and map the extent of suspected deep disease for multidisciplinary counselling and operative planning.
Interpretation and limitations
Both require specialist gynaecological imaging expertise. A negative result reduces the likelihood of mapped deep lesions but cannot rule out superficial or microscopic disease.
04Diagnostic laparoscopy with imaging and selective biopsy
Why
Inspect the pelvis directly when clinical suspicion persists and operative diagnosis or treatment would alter management.
Interpretation and limitations
Differential diagnosis
01
Adenomyosis and fibroids
A bulky tender uterus, heavy bleeding and myometrial imaging changes support adenomyosis, while discrete masses suggest fibroids; either can coexist with endometriosis.
02
Pelvic infection and adhesions
Discharge, infection risk and cervical tenderness support PID, while previous infection or surgery may leave adhesions whose relationship to pain is variable.
03
Bowel or bladder disease
Irritable bowel syndrome, inflammatory bowel disease, constipation, bladder pain syndrome, infection and calculi can fluctuate with the cycle and require symptom-specific testing.
04
Pelvic-floor or neuropathic pain
Insertional pain, muscle overactivity, scar allodynia or burning and shooting qualities indicate additional mechanisms not visible on pelvic imaging.
05
Malignancy
A new complex mass, ascites, weight loss, postmenopausal symptoms or progressive non-cyclical pain requires cancer assessment rather than attribution to known endometriosis.
Management
01Clinical suspicionInvestigate and treat in parallelFirst stepOne or more NICE symptom patterns suggest endometriosis, whether examination is normal or abnormal.+
1Record the cycle, bowel, bladder, sexual, functional and fertility pattern and offer a pain and symptom diary if it would help the person communicate changes.
2Offer transvaginal ultrasound, or transabdominal imaging when needed, while beginning appropriate analgesic or hormonal treatment and addressing immediate quality-of-life needs.
3Give clear information that normal imaging cannot exclude disease and set a review point rather than asking the person to return only when symptoms become intolerable.
02General referralEscalate persistent or impactful symptomsEscalationInitial treatment is ineffective, not tolerated or contraindicated, symptoms recur or impair daily life, or examination shows pelvic signs.+
Complications
01
Subfertility
Inflammation, adhesions, distorted tubo-ovarian anatomy and ovarian endometriomas can reduce spontaneous conception, while ovarian surgery may further affect reserve.
02
Bowel or urinary compromise
Deep disease can obstruct bowel or ureter, cause hydronephrosis and renal loss, or infiltrate bladder, requiring coordinated specialist surgery or organ-protective treatment.
03
Persistent pain and disability
Inflammatory, mechanical, pelvic-floor and sensitisation mechanisms can continue despite hormonal or surgical lesion control and require a multidimensional pain plan.
04
Acute adnexal events
Endometriomas can coexist with torsion, leak or rupture; sudden severe pain, vomiting, peritonism or instability needs acute assessment rather than routine follow-up.
Monitoring and follow-up
Review pain domains separately: dysmenorrhoea, non-menstrual pain, bowel, bladder and sexual pain may respond differently and suggest different anatomy.
Track school, work, sleep, activity, intimacy and quality of life alongside symptom intensity, because treatment success is defined by the person's priorities.
Check ultrasound and referral completion and upgrade the route if an endometrioma, deep disease, extra-pelvic disease or urinary obstruction is identified.
Revisit fertility goals and ovarian reserve before repeat ovarian surgery or prolonged suppressive treatment, involving fertility services when conception is a current priority.
Reassess the differential when pain becomes acutely severe, loses its cyclical pattern, persists after menopause or develops bleeding, mass, bowel obstruction or renal features.
Special situations
Extent and pain diverge
Visible disease stage is an anatomical description rather than a pain scale; small lesions can be painful and extensive deep disease can be unexpectedly quiet.
Imaging is also a routing tool
Finding an endometrioma or deep lesion changes the destination from routine gynaecology toward a specialist centre even before operative confirmation.
CA125 creates false certainty
Its concentration can rise with endometriosis but overlaps broadly with normality and other conditions, so NICE advises against using it diagnostically.
Adolescence is not protective
Severe dysmenorrhoea, school absence and persistent pelvic symptoms in young people deserve timely assessment, adapted examination and age-appropriate specialist referral.
Renal loss can be quiet
Ureteric deep endometriosis may obstruct gradually with limited pain; hydronephrosis or impaired renal function requires urgent organ-protective specialist planning.
Common pitfalls
01
Calling severe dysmenorrhoea normal because it began soon after menarche or the patient is young.
02
Requiring laparoscopic confirmation before offering initial hormonal symptom treatment or referral.
03
Reassuring that a normal pelvic examination or ultrasound excludes endometriosis.
04
Ordering CA125 as a screening or exclusion test for suspected endometriosis.
05
Sending an endometrioma or suspected bowel, bladder or ureteric disease through a routine non-specialist operative pathway.
06
Equating anatomical stage with pain severity, disability, prognosis or the person's preferred treatment.
Investigation, referral and initial pharmacological treatment should proceed in parallel; laparoscopic proof is not required before a supported trial of analgesia or hormonal treatment.
Refer an endometrioma, suspected deep disease involving bowel, bladder or ureter, or disease outside the pelvis to a specialist endometriosis service with imaging, pain, fertility and surgical expertise.
Vomiting, abdominal distension, inability to pass stool or flatus, or severe rectal bleeding suggests bowel obstruction or another gastrointestinal emergency rather than uncomplicated cyclical bowel pain.
Postmenopausal bleeding, a new complex adnexal mass, ascites, weight loss or progressive non-cyclical symptoms must enter the appropriate cancer pathway.
Severe pain with fever, offensive discharge or systemic illness raises pelvic infection, abscess or postoperative complication and requires prompt assessment.
Systematic inspection by an appropriately trained surgeon matters. Histology can confirm lesions and exclude mimics; negative histology or apparently normal laparoscopy needs interpretation in the context of sampling and expertise.
05Renal tract, bowel or fertility assessment
Why
Measure organ impact when urinary obstruction, significant bowel involvement or difficulty conceiving changes the management goal.
Interpretation and limitations
Renal function and tract imaging protect against silent ureteric injury; bowel and fertility tests should be selected by the relevant multidisciplinary pathway rather than used as general screening.
1
Refer to gynaecology with the symptom trajectory, treatments tried, response, imaging, fertility priorities and any limitations of examination documented.
2Continue reasonable symptom treatment during the wait rather than making access to care contingent on laparoscopic confirmation.
3Discuss possible specialist imaging, laparoscopy, surgery and multidisciplinary pain care as options whose value depends on the person's goals.
03Specialist referralRoute complex disease to an endometriosis centreImaging or symptoms suggest an endometrioma, deep bowel, bladder or ureteric involvement, or endometriosis outside the pelvis.+
1Refer to a specialist endometriosis service with advanced laparoscopic, colorectal, urological, imaging, pain, nurse and fertility access.
2DefinitiveMap deep disease with specialist ultrasound or MRI before definitive surgery and assess renal obstruction promptly when the ureter may be affected.
3Use multidisciplinary counselling to compare symptom control, organ protection, ovarian reserve, fertility and operative complication risks.
04Laparoscopic routeMake surgery answer a defined questionSuspicion persists after imaging or treatment, and diagnosis or possible operative treatment will change decisions.+
1Explain alternatives, operative risks, the possibility of a normal examination and which lesions may be treated during the same procedure with prior consent.
2Inspect systematically, document images and obtain histology from suspicious lesions, while avoiding unconsented complex bowel, bladder or ureteric surgery.
3After results, update the diagnosis and plan; if no disease is seen, address pelvic-floor, bladder, bowel, neuropathic and chronic primary pain mechanisms without invalidating symptoms.