eMedicine Specialties > Radiology > Obstetrics/Gynecology

Endometrioma/Endometriosis

Author: Shawn Daly, MD, Consulting Staff, Catalina Radiology, Tucson, Arizona
Coauthor(s): Eric Outwater, MD, Professor, Department of Radiology, University of Arizona
Contributor Information and Disclosures

Updated: Dec 29, 2008

Introduction

Background

Endometriosis is defined as the presence of endometrial glandular tissue outside of the uterus. In contrast, adenomyosis is endometrial tissue within the myometrium. Adenomyosis once was termed endometriosis interna but currently is recognized as a distinct clinical entity.

Two main theories exist for the pathogenesis of endometriosis. One theory is that endometrial tissue is spread by retrograde menstruation or by vascular and/or lymphatic spread. The second theory holds that the serosal epithelium of the peritoneum undergoes metaplastic differentiation into endometrium-like tissue.

The theory that retrograde menstruation causes endometriosis is supported by the analysis of peritoneal fluid in women. As many as 90% of women have blood in the peritoneal fluid during the perimenstrual period. In addition, endometrial cells have been found in the peritoneal fluid. The pattern of endometriosis is consistent with retrograde menstruation and is most common in the ovary, followed by the other dependent areas of the pelvis. Vascular and/or lymphatic spread is supported by noting the occasional distal (extraperitoneal) sites of endometriosis, including the lungs and central nervous system (CNS). In addition, teenage girls with obstructive uterine or vaginal anomalies show retrograde menstrual bleeding, and endometriosis is common in these patients.

Metaplasia is the conversion of peritoneal epithelium into endometrial epithelium. The theory that metaplasia causes endometriosis is supported by the fact that endometrial cells and peritoneal cells derive from the same celomic wall epithelium. This theory also is supported by development of endometriosis in women who lack normal endometrial tissue (ie, in Turner syndrome and uterine agenesis). In addition, rare cases of endometriosis have been found in the prostatic utricle of men. The prostatic utricle is a mullerian remnant.

Clinical presentations of endometriosis often consist of chronic pelvic pain and infertility; however, many patients are asymptomatic.

For excellent patient education resources, visit eMedicine's Women's Health Center. Also, see eMedicine's patient education articles Female Sexual Problems and Endometriosis.

Related eMedicine topics:

Endometriosis (Emergency Medicine)

Endometriosis (Obstetrics & Gynecology)

Endometriosis (Pediatrics: Surgery)

Chronic Pelvic Pain

Uterus, Adenomyosis

Pathophysiology

The pathophysiologic hallmark of endometriosis is the presence of peritoneal implants of ectopic endometrium. The histologic diagnosis of endometriosis is confirmed when 2 of the following 3 features are identified:

• Endometrial glands
• Stroma
• Hemosiderin pigment

The most frequent site of endometriosis is the ovary. Other frequent locations include the following:

• Uterine ligaments
• Pelvic cul-de-sac (pouch of Douglas)
• Pelvic peritoneum
• Fallopian tubes
• Rectosigmoid
• Bladder

Complications of endometriosis consist of bowel and ureteral obstruction resulting from pelvic adhesions. Rarely, endometriosis is extraperitoneal and occurs in the lungs and CNS.

Ectopic endometrial glandular tissue is influenced by ovarian hormones and undergoes cyclic bleeding. The earliest visible manifestations of endometriosis are whitish peritoneal plaques. The foci of endometrial tissue are small subserosal nodules with a brown appearance on gross examination; termed powder burns, they are seen on laparoscopic examination. Over time, the repeated hemorrhaging can produce extensive fibrosis surrounding the endometrial tissue, which can result in adhesions to adnexal structures or to bowel and can obliterate the pelvic cul-de-sac.

When the ovaries are involved, they can become enlarged with cystic, blood-filled spaces that, on gross examination, are termed chocolate cysts, or endometriomas. Endometriomas can become large and multilocular. The endometrial-cell lining can become obliterated over time, making the pathologic distinction between an endometrioma and a hemorrhagic cyst difficult in some cases.

Frequency

United States

Estimates of the frequency in the general population of menstrual-aged females are variable, depending on the population source. This variability may have resulted from sampling bias, since most women with pathologically proven endometriosis who have been included in such statistics have sought evaluation because of pelvic pain and/or fertility problems. A large-scale laparoscopic evaluation of asymptomatic women has never been performed.

In 1 study, 20% of women undergoing laparoscopic evaluation for infertility and 24% of women with pelvic pain had endometriosis. Overall prevalence in symptomatic and asymptomatic women has been estimated to be 1-10%. A hereditary component may be a factor, because an increased prevalence is found among first-degree relatives.

Mortality/Morbidity

The primary morbidity associated with endometriosis relates to chronic pelvic pain and infertility.

The cause of infertility is probably related to tubal dysfunction secondary to endometrial implants. This may be due to fibrosis and to adhesions distorting the tube, but other factors, such as the production of cytokines, may contribute. The severity of symptoms is not closely related to the extent of endometriosis. Mortality is negligible.

Endometriosis in atypical sites can present with various comorbid clinical symptoms. Endometriosis involving the gastrointestinal (GI) tract usually involves the dependent bowel. The endometrial implants begin in the serosa but can erode into the muscularis and cause bowel obstruction or rectal bleeding. More commonly, endometriosis adhesions or endometriomas can obstruct the ureters and cause hydronephrosis. In the rare patient with intrathoracic endometriosis, pneumothorax associated with menses may occur.

Race

No statistically significant race predilection exists for endometriosis.

Sex

Endometriosis occurs primarily in women, with only rare case reports existing of clinically insignificant occurrences of the disease in men.

Age

Endometriosis occurs primarily in women during their reproductive years, most commonly in women aged 25-29 years. Extraperitoneal endometriosis typically occurs in a slightly older population. Endometriosis in women younger than 20 years often is secondary to obstructive anomalies of the uterus or vagina. Endometriosis usually regresses substantially after menopause.

Presentation

Natural history and presentation

Endometriosis most commonly affects the dependent portions of the pelvis. The most frequent site is the ovary, and the next most frequent locations include the uterine ligaments, pelvic cul-de-sac, pelvic peritoneum, fallopian tubes, rectosigmoid, and bladder. Rarely, endometriosis can be extraperitoneal, affecting the lungs and CNS.

Staging of endometriosis depends on the degree and complications of endometrial implants. The 1985 Revised Classification of Endometriosis, created by the American Society for Reproductive Medicine, evaluated the characteristics of endometrial implants, such as location and the depth of penetration, as well as the degree of cul-de-sac obliteration and adhesions. The findings on laparoscopy can be used to classify patients into 4 classes, from mild (stage I) to severe (stage IV). The staging correlates with the likelihood of achieving pregnancy but not with the severity of pain.

Usually, physical examination demonstrates nonspecific pelvic tenderness, although occasionally, tender nodular masses can be palpated in the adnexa or the posterior cul-de-sac. Adhesions can obliterate the cul-de-sac, which correlates with the finding of a frozen pelvis on physical examination. Cystic masses of endometriosis (endometriomas) may present as palpable adnexal masses.

Endometriosis can cause ureteral obstruction and hydronephrosis. This results from endometrial implants on the distal ureter or from mass effect from endometriomas.

It should always be considered that a woman with pelvic pain and/or fertility problems may have more than 1 disease process, such as chronic pelvic inflammatory disease or an adnexal neoplasm.

Young women with endometriosis may have a uterine obstruction and/or malformation as the underlying cause.

Treatment

Treatment for symptomatic endometriosis can be medical or surgical.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently used first in patients with pelvic pain, particularly if the diagnosis of endometriosis has not been definitively established.

The goal of directed medical treatment is to achieve an anovulatory state. This is typically achieved initially using oral contraceptives. This can also be accomplished with a progestational agent (ie, medroxyprogesterone); with danazol, gestrinone, or gonadotropin-releasing hormone agonists (GnRH); or with other less well-known agents. These agents are generally used if oral contraceptives and NSAIDs are ineffective in controlling symptoms. GnRH can be combined with estrogen and progestogen (add-back therapy) without loss of efficacy but with fewer hypoestrogenic symptoms. No evidence exists that any 1 of these agents is most effective in controlling pain; moreover, there is no strong evidence that these drugs improve fertility.

Laparoscopic surgical approaches to endometriosis include the ablation of implants, the lysis of adhesions, and the removal of endometriomas, as well as uterosacral nerve ablation and presacral neurectomy. Conservative surgery can be performed to preserve fertility in young patients. Randomized clinical trials have shown evidence that laparoscopic surgery provides pain relief and improved fertility over diagnostic laparoscopy without surgery. Definitive surgery consists of a hysterectomy and a bilateral oophorectomy.¹

Preferred Examination

The initial workup begins with a history and physical examination. These can be nonspecific, but occasionally, tender, nodular masses can be palpated on pelvic examination, representing fibrotic implants in the cul-de-sac.

Usually, the initial imaging examination for suspected endometriosis is pelvic ultrasound (US) scanning. Magnetic resonance imaging (MRI) provides superior anatomic detail and better defines abnormalities found using ultrasonography.

Laparoscopy is the standard modality for the diagnosis of endometriosis. It is the most sensitive means of examination because only laparoscopy can identify superficial peritoneal implants; however, laparoscopy is an invasive surgical procedure. Laparoscopy can be incorporated into treatments in which endometriomas are cauterized or removed and adhesions are lysed.

Limitations of Techniques

Plain film radiography, computed tomography (CT) scanning, and barium studies are not sensitive for the diagnosis of endometriosis. Moreover, the appearance of implants and endometriomas is nonspecific.

US scanning and MRI are not sensitive for superficial lesions. US scanning is not sensitive for the detection of large implants.

Laparoscopy is limited because it is invasive. In addition, laparoscopy can be limited by the presence of dense pelvic adhesions, resulting in limited access to the cul-de-sac and adnexa.

Differential Diagnoses

Ectopic Pregnancy
Ovarian Torsion
Ovary, Malignant Tumors
Pelvic Inflammatory Disease/Tubo-ovarian Abscess

Other Problems to Be Considered

History and physical examination findings

Pelvic infection
Ovarian cyst
Ovarian torsion
Ovarian neoplasm
Ectopic pregnancy

MRI and US scan findings

Cystic neoplasms
Functional cysts
Hemorrhagic cysts
Cystadenomas

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