Endometriosis Diagnosis: Symptoms, Scans and Laparoscopy

Endometriosis is diagnosed first from the pattern of symptoms and a pelvic examination, then confirmed with a transvaginal ultrasound, supported where needed by CA-125, MRI, cystoscopy or colonoscopy, and proven by laparoscopy and histology. Severe period pain lasting the whole period, deep pain during intercourse and a fixed, tender uterus are the classic clues.

For Dr. Tripti Sharan, Senior Director - Obstetrics & Gynaecology and Head – High Risk Pregnancy, BLK-Max Super Speciality Hospital, New Delhi, India, the order of those steps matters. "Most important is the clinical examination," she told doctors at her masterclass. Imaging and blood tests support a diagnosis that a careful clinician can usually reach at the bedside. This article follows the diagnostic pathway she described, from the first conversation with the patient to the microscope. The complete guide to endometriosis gives the wider picture of causes and management.

The symptoms of endometriosis

Pain that is different from ordinary period pain

Dysmenorrhoea, or painful menstruation, is the most common symptom. The distinction Dr. Sharan draws is one of severity and duration. Many women have some pain with their periods. In endometriosis the pain is very severe, present on all four or five days rather than the first one or two, gets worse over time, and needs repeated doses of painkillers that often fail to relieve it.

Other pain patterns follow the location of the disease:

• Deep pelvic pain and pain during intercourse (dyspareunia), especially on deep penetration. Endometriotic tissue in the pelvic ligaments is stretched during intercourse, producing deep-seated pain.
• Pain on passing urine (dysuria), around the time of the period, when the bladder or urinary tract is involved.
• Pain on opening the bowels (dyschezia), again cyclical, when the bowel is involved. Severe bowel disease can make sitting on the toilet painful.

Abnormal bleeding

Endometriosis of the ovary, including the chocolate cyst, disturbs the hormones the ovaries produce. The result can be any abnormal bleeding pattern: spotting before the period, frequent cycles, or bleeding between periods.

Infertility

Inability to conceive is now the second most common reason women present with endometriosis, after pain. Tubes that are stuck and immobile cannot pick up eggs, affected ovaries may fail to release them, and the inflamed pelvic environment works against sperm and implantation. The mechanisms are covered in the fertility article.

Symptoms at unusual sites

Wherever the tissue lies, it swells and bleeds with the menstrual cycle. Disease in the urinary tract can cause blood in the urine during periods and symptoms that mimic a urinary tract infection. Disease in a caesarean or other surgical scar causes a painful swelling that enlarges and bleeds at the time of menstruation. Disease in the lungs or chest can cause symptoms that follow the cycle.

Dr. Sharan described a patient she is currently treating for umbilical endometriosis. Every month the woman's navel swells and bleeds. "It was really hard to believe," Dr. Sharan said, until the patient came to clinic during her period and showed her the blood coming from the umbilicus. Cases like this explain why cyclical symptoms at any site should prompt the question of endometriosis.

What the examination shows

The physical signs Dr. Sharan looks for on vaginal examination are specific:

• Tenderness behind the uterus, where ovarian and deep pelvic disease most often sits.
• Nodules, which endometriotic tissue forms in the ligaments and tissues behind the uterus.
• A fixed uterus. The normal uterus is a mobile structure that moves easily on examination. When endometriosis binds it to the pelvic walls, it cannot be moved.
• Cystic masses beside the uterus, when there is an ovarian endometrioma.
• Bluish lesions in the vagina, visible directly on speculum examination when the disease involves the vaginal wall.

How endometriosis is diagnosed where scans are scarce

Where scans are scarce, endometriosis can be diagnosed largely on clinical grounds. A doctor from Nigeria asked how to separate endometriosis from other causes of chronic pelvic pain in resource-limited settings, such as areas outside big cities, where diagnostic procedures are not easily available. Dr. Sharan acknowledged the dilemma, noting that India has many resource-starved hospitals as well, and returned to her first principle: the diagnosis should be clinical to a large extent.

The history carries most of the weight. Pain linked to the period, worsening over time, lasting all five days and needing a lot of painkillers; deep pain during intercourse; pain on passing urine or stools at the time of the period. Together these point strongly towards endometriosis. On examination, a fixed uterus or a pelvic mass raises the suspicion further; a mass will still need an ultrasound, but the clinical picture can be built before the scan.

Her most useful discriminator is timing. Other ovarian tumours and other pelvic pathology do not produce symptoms only around menstruation; they cause symptoms at other times too. Cyclical symptoms are the signature of endometriosis.

Transvaginal ultrasound: the key supporting test

The most important investigation, and the one Dr. Sharan uses most, is a transvaginal ultrasound (TVS), in which the probe is placed in the vagina, close to the pelvic organs. An abdominal ultrasound may miss the disease.

On ultrasound an endometrioma typically has a "ground glass" appearance: uniform, low-level echoes from the old blood inside it. Cysts may be small or large. The main task is to tell an endometrioma apart from other ovarian cysts and complex masses, particularly dermoid cysts. That is not usually difficult, though confusion does occur, and an experienced radiologist can generally say with confidence whether a cyst is endometriotic. Colour Doppler, performed during the ultrasound, assesses the blood supply to a lesion.

CA-125: raised, but rarely a cause for alarm

CA-125 is a blood marker measured whenever there is an ovarian mass, including a chocolate cyst. It is often raised in endometriosis. Dr. Sharan's advice to clinicians is to interpret it calmly. CA-125 is best known as a marker of ovarian cancer, which frightens patients, but it also rises in endometriosis, and endometriosis is far more common than ovarian cancer. A raised CA-125 in a woman with a typical endometrioma is not, on its own, a reason for alarm.

Other markers, such as antibodies and tumour necrosis factor (TNF), have been studied but are not routine; Dr. Sharan described them as theoretical.

Further imaging and endoscopy by site

When the history or examination suggests disease beyond the ovaries, the investigation is matched to the site:

• MRI and CT help map deep disease and are needed for disease in the chest and lungs, which ultrasound cannot see.
• Urinary tract. Clinical suspicion is the starting point, especially with symptoms around the period. A routine urine test may show red blood cells; CT urography images the urinary tract; and cystoscopy, a telescope examination of the bladder carried out with urology colleagues, shows endometriotic spots directly. Dr. Sharan considers cystoscopy "a very good procedure" for ruling them out.
• Bowel. Colonoscopy or sigmoidoscopy examines the bowel lining when bowel involvement is suspected.

Laparoscopy: seeing and treating in one procedure

Imaging can miss small lesions. Laparoscopy, in which a telescope is passed into the abdomen through a small incision, shows the whole pelvis under magnification, so small lesions, large lesions and ovarian cysts can all be identified directly. Dr. Sharan described it as the gold standard and an excellent way of diagnosing endometriosis, with the added advantage that treatment can be carried out in the same procedure. Current European guidance (ESHRE, 2022) also accepts ultrasound or MRI findings as a basis for diagnosis, and reserves diagnostic laparoscopy for women whose imaging is negative but whose symptoms continue despite treatment.

At laparoscopy the surgeon sees the disease in its different forms:

• Peritoneal lesions: the dark "powder-burn" or "gunshot" spots and patches of scarring on the pelvic lining.
• Adhesions: bands that stick the tubes and ovaries to the uterus, the pelvic side wall or the bowel. Because endometriotic tissue is old blood, and blood sticks readily, adhesions are very common. They are a major cause of pain and make dissection difficult.
• Endometriomas: chocolate cysts containing altered, dark brown blood, usually adherent to the bowel, the side wall or the uterus.
• Superficial implants: small deposits scattered over the pelvic surfaces.
• Deep infiltrating endometriosis: disease growing into ligaments, cervix, bowel or ureters, the most difficult form to treat because removal carries a risk of injury to those organs.

Surgical treatment of what laparoscopy finds is covered in the treatment article.

Histology: the confirmation

Tissue removed at surgery is sent for histology, examination under the microscope. The diagnostic finding is endometrial glands and stroma, the two components of the uterine lining, in a place they should not be. Glands and stroma in a sample from the ovary confirm endometriosis; in a sample from the bowel, they confirm bowel endometriosis.

Endometriosis or endometriotic cyst?

Endometriosis and an endometriotic cyst are the same disease at different scales. Dr. Sharan made the point when asked whether they are different conditions. An endometriotic lesion may be microscopic, small or larger; when blood collects within it in the ovary, it forms a cyst. An ovarian endometrioma is therefore a large, cystic form of the same disease that elsewhere appears as small, soft lesions.

Endometriosis stages and differential diagnosis

Endometriosis is graded from stage 1 to stage 4 according to its severity: the size and spread of the lesions and the extent of adhesions. The most widely used system, the revised American Society for Reproductive Medicine (rASRM) classification, labels the stages minimal, mild, moderate and severe.

Several conditions produce a similar picture of pelvic pain, masses or adhesions and need to be distinguished:

• Chronic pelvic infection, which also causes adhesions.
• An old ectopic pregnancy, a pregnancy that implanted outside the uterus and has left a mass stuck in the pelvis.
• Inflammatory bowel disease, such as ulcerative colitis or Crohn's disease, when the bowel is involved.

Adenomyosis, endometrial tissue growing within the wall of the uterus, frequently coexists with endometriosis. Dr. Sharan estimated that around 50 to 60% of women with endometriosis have some degree of it. The audience's questions on diagnosis, including the investigation of urinary tract disease, are answered in full in the Live Discussion.