**1. Introduction**

446 Endometriosis - Basic Concepts and Current Research Trends

Stratton P, Winkel C, Premkumar A et al. Diagnostic accuracy of laparoscopy, magnetic

endometriosis. Fertil Steril 2003; 79: 1078-1085

resonance imaging, and histopathologic examimation for the detection of

Endometriosis is one of the most common benign gynaecological conditions. It is defined as the presence of ectopic endometrial glands and stroma outside the uterus. The ectopic endometrium responds to hormonal stimulation with a cyclic hemorrhage, resulting in a complex spectrum of symptoms.

Pain is the cardinal symptom of endometriosis, even though patients may experience several different types of pain, such as dysmenorrhea, deep dyspareunia, discomfort during defecation or while urinating, according to the anatomic location of this disorder. Endometriotic implants, pelvic adhesions and ovarian endometriomas are commonly associated with chronic pelvic pain. Haemorrhage into an endometrioma may result in acute pain. Infertility is another commonly associated complaint.

The exact prevalence of endometriosis is not well defined, as the diagnostic gold standard is represented by laparoscopy or laparotomy. It is estimated about 5-10%, including both symptomatic and asymptomatic women. Nulliparous women and women reporting short and heavy menstrual cycles are at increased risk [1]; these epidemiological findings support the metastatic implantation from retrograde menstruation hypothesis. Other theories include the metaplastic differentiation of serosal surfaces or müllerian remnant tissue, and the induction of undifferentiated mesenchyme to form endometriotic tissue due to released substances from the shed endometrium (induction theory) [2].

The most common locations of endometriosis are the ovaries and the pelvic peritoneum, followed in order of decreasing frequency by deep lesions of the pelvic subperitoneal space, the intestinal system and the urinary system. Deep pelvic endometriosis is a pathologically distinct entity: deep endometriotic lesions penetrate under the surface of peritoneum (infiltration > 5mm) and are tipically found in the uterosacral ligaments, rectum, rectovaginal septum, vagina or bladder, and induce a fibromuscolar hyperplasia that surrounds endometriosis foci [3].

The diagnosis of endometriosis still remains a challenge for clinicians, resulting from similarities in clinical symptoms to other benign or malignant gynaecological diseases.

Laparoscopy is the standard of reference in the diagnosis of endometriosis; histological analysis of biopsy specimens should confirm the diagnosis, even if it is not necessary.

On the other hand, laparoscopy is also required for staging the disease. The most widely used staging system is the 1985 Revised Classification of Endometriosis published by the

Pelvic Endometriosis: A MR Pictorial Review 449

When the peritoneal lesion invades the subserosal layers it progressively leads to extensive fibrosis, wall thickening of the pelvic organs, nodule formation and distortion of the normal pelvic anatomy due to a fibrous retraction; the most severe form is the so called "frozen pelvis", that consists of a huge amount of tissue involving the retro-uterine excavation and causing an extensive infiltration of the posterior pelvis (torus uteri, uterosacral ligaments,

Microscopic appearance of endometriosis is composed of endometrial glands, stroma and occasionally histiocytes, due to an inflammatory response caused by cyclic hemorrhages within the implant. In rare cases endometriosis may lack glands (stromal endometriosis)

Radiologists are often involved in the diagnosis and pre-operative assessment of the disease: an accurate pre-operative evaluation of the endometrial implants (location, size and depth of penetration) could help the surgeon to perform a radical surgical excision in cases in which severe fibrosis and adhesions hide deep lesions and impede laparoscopic

Imaging methods that are used in the daily practice to diagnose endometriosis are ecotomografy, especially Transvaginal Ultrasound (TVUS) and Magnetic Resonance

TVUS provides high resolution images of the pelvic organs, providing reliable information

TVUS has been reported to be the best method for discriminating between endometriotic and non-endometriotic cysts, with a sensitivity of 83% and a false positive rate of 7%. The addition of CA-125 evaluation does not improve the diagnostic accuracy of TVUS, thus indicating TVUS alone to be the least expensive instrument for identifying the presence of

The role of TVUS for the assessment of deep pelvic endometriosis has been recently reported, with conflicting results. TVUS is apparently more accurate than Rectal Endoscopic Ultrasound (RES) for predicting deep pelvic endometriosis in specific locations and should be the first line imaging method in this setting [10]. RES appears to be the best technique for

The role of MRI in the diagnosis of endometriosis has increased after 1987, when Nishimura *et al. [12]* demonstrated the value of this imaging method in the diagnosis of endometriomas. Then the use of MRI for the evaluation of deep endometriosis was proposed by Siegelman *et al. [13]*, who studied its role in analysing solid pelvic masses. More recently other investigators [14] showed the promising results of MRI for the specific

Also dynamic MR imaging has been tested for this purpose, showing a good accuracy in the differential diagnosis of nodular endometriosis from other pathologic conditions of

The classic endometrioma on TVUS appears as an area of low and homogenous echoes.

vaginal and rectal wall).

**3. Radiologic evaluation of endometriosis** 

in patients with both acute and chronic pelvic pain [7].

evaluating the depth of bowel infiltration by endometriosis [11].

[6].

evaluation.

Imaging (MRI).

endometriomas [8,9].

evaluation of deep endometriosis.

abdominal wall and pelvis [15].

American Fertility Society [4]. The rAFS score takes into account the presence of ovarian and peritoneal implants (subdivided into superficial or deep), the severity of the adhesions and the presence or not of a complete posterior cul-de-sac obliteration (i.e. frozen pelvis). The rAFS staging system has shown poor correlation to the clinical severity of the disease, so requiring further refinement. Meanwhile a new staging system called ENZIAN score has been recently developed [5]; it is focused on the deep pelvic endometriosis that is the most severe form of the disease.

The clinical value of this staging system and its correlation to the reproductive prognosis of endometriosis patients should be assessed.

Therapeutic options are observation, medical treatment, surgery or a combination strategy.

The most widely used medical therapy of endometriosis includes oral contraceptives, androgenic agents, progestins, and gonadotropin releasing hormone (GnRH) analogs. The choice of a surgical option depends upon the severity of the disease. Surgery is the main therapeutic option in patients with deep pelvic endometriosis. Anterior cul-de-sac endometriosis involving the bladder can be treated with laparoscopic surgery. Preoperative staging of disease is necessary because in certain cases surgery should be performed by standard laparotomy (bladder endometriosis associated with bowel involvement). Treatment of posterior cul-de-sac endometriosis can be achieved with laparoscopy, but a vaginal or a laparotomic approach is needed when vaginal or severe bowel disease, respectively are present.
