The Endometriosis Glossary | ESSI

The ESSI Endometriosis Glossary: A Comprehensive Guide

A Note to Our Community: While this glossary is one of the most comprehensive available, the language of endometriosis is constantly evolving with new research and deeper understanding. We are committed to staying at the forefront of this field, continuously learning from scientific discovery and, most importantly, from the invaluable insights of our patient community. We look forward to updating this resource and sharing these new concepts as we all move forward together.

Navigating the world of endometriosis—whether as a patient, a dedicated advocate, or a clinician—can often feel like learning a new language. The terminology is complex, specific, and can be intimidating.

At Endometriosis Surgical Specialists International (ESSI), we believe knowledge is power. Understanding the vocabulary of this disease is the first step toward clear communication, effective advocacy, and receiving the highest standard of care. This glossary is designed to be a definitive resource for our entire community.

Part 1: Foundational Concepts & Theories

• Endometriosis: A chronic, inflammatory disease where tissue similar to the lining of the uterus (the endometrium) grows outside of the uterus. This tissue creates inflammation, scar tissue (fibrosis), and adhesions, leading to pain and other symptoms.
• Endometrium: The tissue that normally lines the inside of the uterus, which builds up and sheds each month during menstruation.
• Lesion / Implant: The terms for an individual area or patch of endometriosis tissue found outside the uterus.
• Inflammation: A core process of endometriosis. The body’s immune system reacts to the misplaced tissue, causing a cascade of inflammatory responses that lead to pain, swelling, and tissue damage.
• Estrogen-Dependent Disease: Endometriosis lesions are fueled by estrogen. This is why many medical treatments focus on suppressing estrogen production or blocking its effects.
• Fibrosis: The thickening and scarring of connective tissue, which is a key component of endometriosis lesions. This process contributes to the formation of deep nodules and the “tethering” of organs.
• Retrograde Menstruation: The leading theory for how endometriosis begins. It suggests that during menstruation, some blood and endometrial cells flow backward through the fallopian tubes and into the pelvic cavity, where they can implant and grow.
• Müllerianosis / Embryonic Rest Theory: An alternative theory suggesting that endometriosis may arise from misplaced embryonic cells that were seeded in the pelvis during fetal development.

Part 2: The Language of Symptoms & Diagnosis

• The “Dys”s: These are clinical terms for painful functions.
  • Dysmenorrhea: Painful menstruation.
  • Dyspareunia: Painful intercourse.
  • Dyschezia: Painful bowel movements.
  • Dysuria: Painful urination.
• Chronic Pelvic Pain (CPP): Widespread pelvic pain that lasts for six months or longer and is not exclusively related to menstruation.
• Endo Belly: The characteristic and often severe bloating, distension, and water retention associated with endometriosis, caused by widespread inflammation.
• Leg Pain / Sciatica: Sharp, radiating pain down the leg, which can be caused by endometriosis lesions irritating or infiltrating the large pelvic nerves, like the sciatic nerve.
• Laparoscopy: A minimally invasive surgery where a thin, lighted camera (laparoscope) is inserted into the abdomen to directly visualize and treat pelvic organs. It is the gold standard for diagnosing and treating endometriosis.
• Surgical Staging (ASRM Stage I-IV): A classification system that scores endometriosis based on the location, size, and depth of lesions seen during surgery. Important Note: The stage (I-Minimal, II-Mild, III-Moderate, IV-Severe) does not correlate with the level of a patient’s pain or symptoms.
• Histology / Pathology: The microscopic examination of tissue removed during surgery. A definitive diagnosis of endometriosis requires a pathologist to identify both glandular and stromal cells in the tissue sample.
• Imaging Terms:
  • Transvaginal Ultrasound: An imaging technique used to get a detailed view of the uterus and ovaries. It is often the first step in an evaluation.
  • MRI (Magnetic Resonance Imaging): A more advanced imaging technique that can help identify deep infiltrating endometriosis and map out disease before surgery.

Part 3: The Anatomy of the Disease

• Peritoneum: The thin membrane that lines the abdominal and pelvic cavities and covers most of the organs. This is the most common location for superficial endometriosis lesions.
• Superficial Peritoneal Endometriosis: Endometriosis lesions that are found on the surface of the peritoneum.
• Ovarian Endometrioma (“Chocolate Cyst”): A cyst on or in an ovary that is filled with old, dark blood, giving it a thick, tarry appearance.
• Deep Infiltrating Endometriosis (DIE): A severe form of the disease where lesions penetrate more than 5mm beneath the peritoneum, often forming hard, fibrous nodules that can invade organs like the bowel, bladder, and ligaments.
• Diaphragmatic Endometriosis: Endometriosis found on the diaphragm, the muscle separating the chest from the abdomen. It can cause shoulder, neck, and chest pain, particularly during menstruation.
• Cul-de-sac / Pouch of Douglas: The space between the uterus and the rectum. It is one of the most common locations for deep infiltrating endometriosis.
• Uterosacral Ligaments: The supportive ligaments that connect the cervix to the sacrum. They are a very common site for deep, painful endometriosis nodules.
• Adhesions: Bands of fibrous scar tissue that can form as a result of inflammation from endometriosis. They can cause organs to stick together, leading to pain and dysfunction.
• Adenomyosis: A condition where endometrial tissue grows into the muscular wall of the uterus (the myometrium), causing the uterus to become enlarged, bulky, and painful. It is often considered a “sister” condition to endometriosis.

Part 4: Treatment & Management Vocabulary

• Excision Surgery: The surgical gold standard for endometriosis. It involves meticulously cutting out and removing the endometriosis lesions at their root, preserving healthy tissue.
• Ablation (or Fulguration): A surgical technique that uses heat to burn or vaporize the surface of endometriosis lesions. It is often less effective than excision as it can leave diseased tissue behind.
• Bowel Resection & Reanastomosis: A surgical procedure for severe bowel endometriosis where the affected segment of the bowel is removed (resection) and the two healthy ends are reconnected (reanastomosis).
• Ureterolysis: A delicate surgical procedure to free the ureter (the tube that carries urine from the kidney to the bladder) from surrounding adhesions or endometriosis tissue.
• Hysterectomy / Oophorectomy: Surgical removal of the uterus (hysterectomy) and/or ovaries (oophorectomy). These are treatments for conditions like adenomyosis or are sometimes performed in complex endo cases, but they do not cure endometriosis found elsewhere in the pelvis.
• Medical Management / Hormonal Suppression: The use of medications (like birth control pills, progestins, or GnRH modulators) to suppress the menstrual cycle and slow the growth of estrogen-dependent lesions. This manages symptoms but does not remove the disease.
• GnRH Agonists / Antagonists: Specific classes of drugs (e.g., Lupron, Orilissa) that suppress estrogen production by the ovaries, inducing a temporary, reversible menopause-like state.
• Aromatase Inhibitors: A class of drugs that block the conversion of other hormones into estrogen, effectively reducing estrogen levels throughout the body.

Part 5: Advanced Clinical & Pathological Concepts

• Silent Endometriosis: Endometriosis that is discovered incidentally during a surgery for another reason in a patient who has no pain symptoms.
• Phantom Periods: The experience of cyclical symptoms (pain, bloating) even after a hysterectomy, often caused by remaining endometriosis lesions or ovarian remnants responding to hormonal cycles.
• Catamenial Symptoms: Symptoms that occur cyclically with menstruation but involve organs outside the pelvis, such as a Catamenial Pneumothorax (collapsed lung).
• Nerve Entrapment / Neuropelveology: The study and treatment of pelvic nerve disorders. Endometriosis can directly invade or cause inflammation that entraps pelvic nerves, requiring specialized surgical techniques to free them.
• Central Sensitization: A condition where the central nervous system becomes hyper-sensitive. After years of enduring chronic pain from endometriosis, the brain and spinal cord can amplify pain signals, meaning pain is felt even when the original source is gone.
• Surgical Menopause: Menopause that is induced by the surgical removal of both ovaries, causing an abrupt stop to estrogen production.
• Glandular Epithelium & Stroma: The two specific types of cells a pathologist must identify under a microscope to confirm a diagnosis of endometriosis.
• Hemosiderin-Laden Macrophages: Immune cells containing iron deposits from old blood. Their presence in a biopsy is a cellular marker of previous bleeding within a lesion.

Part 6: Associated & Comorbid Conditions

• Infertility: Difficulty conceiving, which can be caused by endometriosis through inflammation, adhesions that distort anatomy, or by affecting egg quality.
• Pelvic Floor Dysfunction: A condition where the pelvic floor muscles are too tight (hypertonic) or uncoordinated, often as a protective response to chronic pain. It can cause pain, and urinary and bowel issues.
• Interstitial Cystitis / Bladder Pain Syndrome (IC/BPS): A condition causing chronic bladder pain and urinary urgency/frequency. It often co-exists with endometriosis.

Part 7: Your Multidisciplinary Care Team

True world-class endometriosis care requires a team approach.

• Endometriosis Specialist / Excision Surgeon: A gynecological surgeon with advanced training and a primary focus on the surgical excision of endometriosis.
• Colorectal Surgeon: A surgeon specializing in the bowel, who is essential when endometriosis deeply invades the rectum or colon.
• Urologist: A surgeon specializing in the urinary system, necessary for cases involving the bladder or ureters.
• Neurogynecologist: A specialist at the intersection of gynecology and neurology who focuses on pelvic nerve pain and dysfunction.
• Gastrointestinal (GI) Specialist: A doctor who helps manage digestive symptoms and rule out other bowel conditions.
• Pain Management Specialist: A doctor who specializes in treating chronic pain, often using a combination of medication, procedures, and therapies.
• Pelvic Floor Physical Therapist: A therapist with specialized training in treating the pelvic floor muscles.
• Radiologist: A doctor who specializes in reading and interpreting medical images like MRI and ultrasound.