Endometriosis affects between 5 and 45% of women in reproductive age, is associated with significant morbidity, and constitutes a major public health concern. The correct diagnosis is fundamental in defining the best treatment strategy for endometriosis. Therefore, non-invasive methods are required to obtain accurate diagnoses of the location and extent of endometriotic lesions. Transvaginal sonography and magnetic resonance imaging are used most frequently to identify and characterise lesions in endometriosis. Subjective impression by an experienced sonologist for identifying endometriomas by ultrasound showed a high accuracy. Adhesions can be evaluated by real-time dynamic transvaginal sonography, using the sliding sign technique, to determine whether the uterus and ovaries glide freely over the posterior and anterior organs and tissues. Diagnosis is difficult when ovarian endometriomas are absent and endometriosis causes adhesions and deep infiltrating nodules in the pelvic organs. Magnetic resonance imaging seems to be useful in diagnosing all locations of endometriosis, and its diagnostic accuracy is similar to those obtained using ultrasound. Transvaginal ultrasound has been proposed as first line-line imaging technique because it is well accepted and widely available. The main limitation of ultrasound concerns lesions located above the rectosigmoid junction owing to the limited field-of-view of the transvaginal approach and low accuracy in detecting upper bowel lesions by transabdominal ultrasound. A detailed non-invasive diagnosis of the extension in the pelvis of endometriosis can facilitate the choice of a safe and adequate surgical or medical treatment.
Introduction
Endometriosis is estimated to affect between 5% and 45% of women of reproductive age, is associated with significant morbidity, and constitutes a major public health concern . Symptoms of women with pelvic endometriosis are chronic pelvic pain, dysmenorrhoea, dyspareunia, dyschezia, urinary symptoms, and infertility.
Three different forms of endometriosis exist: ovarian endometriosis (endometrioma), peritoneal endometriosis and adhesions, and deep endometriosis. Pelvic endometriosis, especially in severe stages, is strongly associated with adenomyosis, which plays an important role in causing dysmenorrhoea, menorrhagia, and infertility in women with endometriosis.
Ovarian lesions are the most frequent localisation of endometriotic tissue, causing typical ovarian cysts. Deep infiltrating endometriosis (DIE) is defined as an endometriotic lesion infiltrating the peritoneum and penetrating into the retroperitoneal space or the wall of the pelvic organs to a depth of at least 5 mm , and affects between 4 and 37% of women with endometriosis. These different forms of presentation are likely to have different imaging patterns, which may cause specific imaging diagnostic problems. Several systems scores have been used to stage the extension of endometriosis in relation to different locations inside the pelvis. The most common system used to evaluate the disease is the revised classification system of the American Society of Reproductive Medicine (rASRM), which followed the American Fertility Society (AFS) score . As with other systems, this classification does not consider adenomyosis as part of the disease, which remains after surgical treatment of extra-uterine lesions, with persistence of symptoms related to pelvic endometriosis.
The interval between the onset of first symptoms and clinical diagnosis of endometriosis is about 7–10 years . The main diagnostic problems for endometriosis are the detection of the disease, especially in the absence of an endometriotic cyst or in the case of minimal lesions, and also the evaluation of the extent of the disease. The patient’s history and symptoms, a pelvic examination, along with the experience of the sonographer or radiologist, could improve diagnostic accuracy in the diagnosis of pelvic endometriosis.
The correct diagnosis is fundamental to defining the best treatment strategy for endometriosis; therefore, non-invasive methods are required to obtain accurate diagnoses of the location and extent of endometriotic lesions. Two imaging modalities are used most frequently to identify and characterise lesions in endometriosis: transvaginal sonography and magnetic resonance imaging.
Transvaginal ultrasonography has been proposed as the first line-line imaging technique because it allows extensive exploration of the pelvis; it is well accepted and widely available.
Magnetic resonance imaging (MRI) is used as a second-line of investigation in the study of the female pelvis. The role of MRI in the evaluation of endometriosis, especially DIE, has been widely demonstrated. MRI is carried out in selected women according to the outcome of transvaginal ultrasound imaging and the severity of symptoms. Many investigators have studied the role of MRI in the evaluation of deep implants located in the anterior compartment, recto-vaginal septum, posterior vaginal fornix, and bowel wall, especially for the lesions located above the rectosigmoid junction.
Other diagnostic procedures, such as rectal sonography, barium enema, or computed tomography urography play complementary roles in the identification of endometriosis, depending on the site affected, and could be useful in the choice of surgical approach. Transabdominal ultrasound is not accurate in detecting endometriosis, mainly because of bowel gas and adhesions that may reduce the ability to evaluate the pelvic organs. In particular, DIE mostly has retroperitoneal or bowel lesions, which are difficult to see with transabdominal ultrasound probes .
A detailed non-invasive examination of the pelvis to assess the extension of the endometriosic lesions can facilitate the choice of a safe and adequate surgical or medical strategy .
Endometrioma
Diagnostic imaging and implications for treatment
The correct diagnosis of an endometrioma is important because an association exists between endometrioma, endometriosis, and chronic pelvic pain and subfertility. Moreover, an endometrioid adenocarcinoma or clear-cell carcinoma may develop in endometriomas .
Transvaginal sonography has dramatically improved the ability to diagnose ovarian lesions, providing reliable criteria and indications for surgery . The bizarre echogenicity of some endometriomas can erroneously suggest malignancy and vice versa . Therefore, diagnostic criteria to distinguish ovarian endometriomas from other ovarian lesions seem to be of utmost importance. Endometriomas were treated in the past mostly by surgical excision. In cases of recurrence, surgery was repeated, subsequently causing great problems on ovarian reserve. For ovarian endometriosis, first-line treatment is medical treatment and surgery carried out only in cases of suspected malignancy or persistence of symptoms and infertility .
Ultrasound features
Endometrioma
Ultrasound characteristics of endometriomas have been described in several studies, and an attempt has been made to define their typical ultrasound features . The ‘typical’ endometrioma is a unilocular or multilocular (less than five locules) cyst, with homogeneous low-level echogenicity (ground glass echogenicity) of the cyst fluid. Because endometriomas are usually poorly vascularised, power or color Doppler ultrasound examination might help to achieve a correct diagnosis . ( Fig. 1 ). Morphologic features other than the ‘typical’ ones have also been described . Guerriero et al. and Dogan et al. were the first to conduct studies to characterise these atypical endometriomas. The algorithm by Guerriero et al. defines an endometrioma as either a unilocular cyst with ground glass echogenicity and no to moderate vascularisation (‘typical’ endometrioma) ( Fig. 1 ) or as a unilocular cyst with ground glass echogenicity and papillary projections (protrusion of solid tissue into the cyst lumen with a height of 3 mm or more), and no flow inside the papillary projection (‘atypical’ endometrioma). In fact, these are not true papillations of solid tissue but images created from blood clots or fibrin lying adjacent to the cyst wall, showing a more regular surface and round shape of the protrusion ( Fig. 2 ).
According to the algorithm by Guerriero et al. , a unilocular cyst with ground glass echogenicity and strong vascularisation or a unilocular-solid cyst with ground glass echogenicity and a papillary projection with detectable flow or strong vascularisation are classified as non-endometriomas.
Almost 50% of the endometriomas had other ultrasound characteristics than the typical ‘unilocular cyst with ground glass echogenicity of the cyst fluid’.
The rule: ‘premenopausal status, ground glass echogenicity, one to four locules and no papillations with detectable blood flow’ characterise endometriomas reasonably well, but not as well as subjective impression . Serum CA-125 levels are not generally useful in distinguishing endometriomas from other benign tumours and malignancies . They could possibly help to distinguish endometriomas from other benign lesions .
In addition, ultrasound appearance of endometriomas differ between pre- and post-menopausal women. Endometriomas in the postmenopausal women are less frequently unilocular cysts, and are less likely to exhibit ground glass echogenicity . Instead, they are more often multilocular-solid tumours, and more frequently exhibit anechoic cyst fluid or cyst fluid with mixed echogenicity.
Endometriomas may be misinterpreted, potentially because of the complex echotexture, thick walls, and solid echogenic appearance of haemorrhagic clots within the endometrioid cystic cavity, which mimic different dermoid cyst patterns or malignancy. Also, some hyperechoic solid masses (e.g. fibroids and fibrothecomas) can be misdiagnosed as endometriotic cysts. Inversely, some endometriomas can be mistaken for serous cysts, dermoids, and suspected ovarian malignant tumours. The use of colour or power Doppler detecting the presence, number, and distribution of vessels in the solid echogenic protrusions of the cyst wall seems to be useful in differentiating endometriomas from malignant lesions . Unfortunately the use of colour Doppler evaluation has some limitations , because it requires optimal colour Doppler settings, a high quality of the colour Doppler function of the ultrasound equipment used and an experienced ultrasound examiner. Therefore, the absence of vascularisation does not guarantee that the cyst is benign.
The clinical rule that considers endometrioma a cyst with ground glass echogenicity 1-4 septa, with no solid parts, in a premenopausal woman, is useful in most clinical settings because it allows the examiner to skip the colour Doppler assessment of the mass. This clinical rule has almost as good discriminatory power as the statistically optimal rule, but its sensitivity is lower . Finally all the principal rules have a sensitivity ranging from 62–73%, a specificity of 94–98%, and a positive predictive value of 76–89% . Subjective impression by an experienced sonologist was better for identifying endometriomas (positive predictive value 88.5%, positive likelihood ratio 30.2, sensitivity 81%, specificity 97%) . This is probably because the ultrasound examiner uses other available clinical information (e.g. pain and dysmenorrhoea) when suggesting a diagnosis, taking into account other ultrasound findings.
Endometriomas and malignancy
Subjective impression can lead to the misclassification of malignancies as endometriomas in 0.2–0.9% of cases . Ultrasound characteristics of endometriomas differ in pre- and postmenopausal women. Masses in postmenopausal women, whose cystic contents have a ground glass appearance, have a high risk of malignancy.
Endometriomas could serve as precursors of endometrioid borderline ovarian tumours. Endometrioid borderline ovarian tumours have the potential to progress to low-grade invasive carcinoma. Although clear-cell borderline ovarian tumours have been associated with endometriosis, a stepwise molecular pathway for the progression of endometriosis to clear carcinoma has not yet been identified .
Borderline tumours and carcinomas arising from endometrioid cysts show a vascularised solid component at ultrasound examination ( Fig. 3 ). The presence of typical sonographic features for ovarian malignant lesions suggests that benign endometrioid cysts and malignant and borderline tumours arising from endometriosis might be easier to assess by an expert ultrasound examiner compared with normal ovarian masses . This is not the case with ovarian cysts found during pregnancy, were differentiation between borderline tumours and decidualised endometriotic cysts can be more difficult. Ultrasound examiners should always take into account the phenomenon of decidualisation, which is a major contributory factor to incorrect diagnosis in pregnant women . Most decidualised endometriomas (82%) were described as manifesting vascularised rounded papillary projections with a smooth contour in an ovarian cyst with one or more cyst locules and ground glass, or low level echogenicity of the cyst fluid .
Endometriomas and tubal pathology
Where endometrioma or pelvic endometriosis are present, the salpinges can also often be affected by the disease. Adhesions can alter the normal tubal course or occlude the tube, and endometriotic foci can affect the tubal walls. Consequently, a sactosalpinx can be observed near the endometrioma. The typical aspect is a dilated Fallopian tube with thick walls and incomplete septa, seen as a cogwheel-shaped structure (‘cogwheel’ sign) and visible in the cross-section, with a fluid-dense content . Sometimes, the chronic disease can cause a hydrosalpinx with the typical ‘beads-on-a-string’ sign, defined as hyperechoic mural nodules measuring about 2–3 mm and seen on cross-section of the fluid-filled distended structure . ( Fig. 4 ). The presence of hydrosalpinx in infertile women is an indication for surgical removal of the Fallopian tubes . It is important to assess tubal status in cases of endometrioma or DIE by ultrasound.
Endometriosis that affects the ovary and Fallopian tubes can create a tubo–ovarian complex, in which the ovaries and tubes are identified and recognised, but the ovaries cannot be separated by pushing the tube with the vaginal probe. Rarely, the normal architecture of one or both the adnexa and tubes cannot be recognised, and a conglomerate of endometric cysts form; however, neither the ovary nor the tubes can be separately identified .
Endometrioma
Diagnostic imaging and implications for treatment
The correct diagnosis of an endometrioma is important because an association exists between endometrioma, endometriosis, and chronic pelvic pain and subfertility. Moreover, an endometrioid adenocarcinoma or clear-cell carcinoma may develop in endometriomas .
Transvaginal sonography has dramatically improved the ability to diagnose ovarian lesions, providing reliable criteria and indications for surgery . The bizarre echogenicity of some endometriomas can erroneously suggest malignancy and vice versa . Therefore, diagnostic criteria to distinguish ovarian endometriomas from other ovarian lesions seem to be of utmost importance. Endometriomas were treated in the past mostly by surgical excision. In cases of recurrence, surgery was repeated, subsequently causing great problems on ovarian reserve. For ovarian endometriosis, first-line treatment is medical treatment and surgery carried out only in cases of suspected malignancy or persistence of symptoms and infertility .
Ultrasound features
Endometrioma
Ultrasound characteristics of endometriomas have been described in several studies, and an attempt has been made to define their typical ultrasound features . The ‘typical’ endometrioma is a unilocular or multilocular (less than five locules) cyst, with homogeneous low-level echogenicity (ground glass echogenicity) of the cyst fluid. Because endometriomas are usually poorly vascularised, power or color Doppler ultrasound examination might help to achieve a correct diagnosis . ( Fig. 1 ). Morphologic features other than the ‘typical’ ones have also been described . Guerriero et al. and Dogan et al. were the first to conduct studies to characterise these atypical endometriomas. The algorithm by Guerriero et al. defines an endometrioma as either a unilocular cyst with ground glass echogenicity and no to moderate vascularisation (‘typical’ endometrioma) ( Fig. 1 ) or as a unilocular cyst with ground glass echogenicity and papillary projections (protrusion of solid tissue into the cyst lumen with a height of 3 mm or more), and no flow inside the papillary projection (‘atypical’ endometrioma). In fact, these are not true papillations of solid tissue but images created from blood clots or fibrin lying adjacent to the cyst wall, showing a more regular surface and round shape of the protrusion ( Fig. 2 ).
According to the algorithm by Guerriero et al. , a unilocular cyst with ground glass echogenicity and strong vascularisation or a unilocular-solid cyst with ground glass echogenicity and a papillary projection with detectable flow or strong vascularisation are classified as non-endometriomas.
Almost 50% of the endometriomas had other ultrasound characteristics than the typical ‘unilocular cyst with ground glass echogenicity of the cyst fluid’.
The rule: ‘premenopausal status, ground glass echogenicity, one to four locules and no papillations with detectable blood flow’ characterise endometriomas reasonably well, but not as well as subjective impression . Serum CA-125 levels are not generally useful in distinguishing endometriomas from other benign tumours and malignancies . They could possibly help to distinguish endometriomas from other benign lesions .
In addition, ultrasound appearance of endometriomas differ between pre- and post-menopausal women. Endometriomas in the postmenopausal women are less frequently unilocular cysts, and are less likely to exhibit ground glass echogenicity . Instead, they are more often multilocular-solid tumours, and more frequently exhibit anechoic cyst fluid or cyst fluid with mixed echogenicity.
Endometriomas may be misinterpreted, potentially because of the complex echotexture, thick walls, and solid echogenic appearance of haemorrhagic clots within the endometrioid cystic cavity, which mimic different dermoid cyst patterns or malignancy. Also, some hyperechoic solid masses (e.g. fibroids and fibrothecomas) can be misdiagnosed as endometriotic cysts. Inversely, some endometriomas can be mistaken for serous cysts, dermoids, and suspected ovarian malignant tumours. The use of colour or power Doppler detecting the presence, number, and distribution of vessels in the solid echogenic protrusions of the cyst wall seems to be useful in differentiating endometriomas from malignant lesions . Unfortunately the use of colour Doppler evaluation has some limitations , because it requires optimal colour Doppler settings, a high quality of the colour Doppler function of the ultrasound equipment used and an experienced ultrasound examiner. Therefore, the absence of vascularisation does not guarantee that the cyst is benign.
The clinical rule that considers endometrioma a cyst with ground glass echogenicity 1-4 septa, with no solid parts, in a premenopausal woman, is useful in most clinical settings because it allows the examiner to skip the colour Doppler assessment of the mass. This clinical rule has almost as good discriminatory power as the statistically optimal rule, but its sensitivity is lower . Finally all the principal rules have a sensitivity ranging from 62–73%, a specificity of 94–98%, and a positive predictive value of 76–89% . Subjective impression by an experienced sonologist was better for identifying endometriomas (positive predictive value 88.5%, positive likelihood ratio 30.2, sensitivity 81%, specificity 97%) . This is probably because the ultrasound examiner uses other available clinical information (e.g. pain and dysmenorrhoea) when suggesting a diagnosis, taking into account other ultrasound findings.
Endometriomas and malignancy
Subjective impression can lead to the misclassification of malignancies as endometriomas in 0.2–0.9% of cases . Ultrasound characteristics of endometriomas differ in pre- and postmenopausal women. Masses in postmenopausal women, whose cystic contents have a ground glass appearance, have a high risk of malignancy.
Endometriomas could serve as precursors of endometrioid borderline ovarian tumours. Endometrioid borderline ovarian tumours have the potential to progress to low-grade invasive carcinoma. Although clear-cell borderline ovarian tumours have been associated with endometriosis, a stepwise molecular pathway for the progression of endometriosis to clear carcinoma has not yet been identified .
Borderline tumours and carcinomas arising from endometrioid cysts show a vascularised solid component at ultrasound examination ( Fig. 3 ). The presence of typical sonographic features for ovarian malignant lesions suggests that benign endometrioid cysts and malignant and borderline tumours arising from endometriosis might be easier to assess by an expert ultrasound examiner compared with normal ovarian masses . This is not the case with ovarian cysts found during pregnancy, were differentiation between borderline tumours and decidualised endometriotic cysts can be more difficult. Ultrasound examiners should always take into account the phenomenon of decidualisation, which is a major contributory factor to incorrect diagnosis in pregnant women . Most decidualised endometriomas (82%) were described as manifesting vascularised rounded papillary projections with a smooth contour in an ovarian cyst with one or more cyst locules and ground glass, or low level echogenicity of the cyst fluid .
Endometriomas and tubal pathology
Where endometrioma or pelvic endometriosis are present, the salpinges can also often be affected by the disease. Adhesions can alter the normal tubal course or occlude the tube, and endometriotic foci can affect the tubal walls. Consequently, a sactosalpinx can be observed near the endometrioma. The typical aspect is a dilated Fallopian tube with thick walls and incomplete septa, seen as a cogwheel-shaped structure (‘cogwheel’ sign) and visible in the cross-section, with a fluid-dense content . Sometimes, the chronic disease can cause a hydrosalpinx with the typical ‘beads-on-a-string’ sign, defined as hyperechoic mural nodules measuring about 2–3 mm and seen on cross-section of the fluid-filled distended structure . ( Fig. 4 ). The presence of hydrosalpinx in infertile women is an indication for surgical removal of the Fallopian tubes . It is important to assess tubal status in cases of endometrioma or DIE by ultrasound.
Endometriosis that affects the ovary and Fallopian tubes can create a tubo–ovarian complex, in which the ovaries and tubes are identified and recognised, but the ovaries cannot be separated by pushing the tube with the vaginal probe. Rarely, the normal architecture of one or both the adnexa and tubes cannot be recognised, and a conglomerate of endometric cysts form; however, neither the ovary nor the tubes can be separately identified .
Magnetic resonance imaging features
Endometrioma
Magnetic resonance imaging for endometriotic ovarian cyst is requested in selected cases if ultrasound outcome is inconclusive, if malignant transformation is suspected, or both. It presents a high specificity in diagnosing endometriomas (98%) , owing to its ability to characterise haemorrhage. ‘Shading’ is a specific sign of endometrioma; it is caused by old blood products, which contain extremely high iron and protein concentrations. These haemorrhagic cysts typically show high signal intensity on T1-weighted images and variable low signal intensity on T2-weighted images. Shading varies from a faint signal to a no signal at all. Solid components, clots, thick septa, and fluid-fluid levels may also be observed at MRI . In these cases, the investigation should be completed with contrast-enhanced sequences to assess the risk of neoplastic transformation.
Tubal endometriosis
Hyperintense tubal fluid seen on T1-weighted images, with or without evidence of endometriosis elsewhere in the pelvis, is suggestive of hydrosalpinx associated with endometriosis. On T2-weighted MRI scans, signal intensity within the fallopian tube is generally high owing to the typical signal intensity of an endometrial cyst, which displays moderate to marked shading. Haematosalpinx has been reported to be an indicator of pelvic endometriosis, and may be the only imaging finding indicative of endometriosis .
Adhesions
Diagnostic imaging and implications for treatment
Ovarian endometriomas are frequently associated with other endometriotic lesions , such as adhesions and DIE, which are not easy to diagnose. Underestimation of extensive adhesions in women with endometriomas before surgery is one of the main reasons why surgery is often incomplete , leading to repeat operations.
Advances in endoscopic surgery have permitted laparoscopic treatment of ovarian cysts that previously required laparotomy and, at present, laparoscopic management of ovarian endometriosis is the technique of choice. Adhesions and DIE lesions, however, remain the most important limitation in the surgical treatment of endometriosis . This limitation obviously differs according to the surgeon’s experience and skill. It seems important, therefore, that preoperative patient selection should be managed according to pelvic extension of the disease. Women with severe disease and extensive adhesions could, therefore, be referred to centres of excellence to ensure complete surgical excision, which requires particular laparoscopic surgical skills and experience .
Ultrasound evaluation
Endometriosis is often associated with the presence of pelvic adhesions. Ultrasound diagnosis in the evaluation of pelvic adhesions in the presence of ovarian endometriosis is a diagnostic challenge. This diagnostic impasse is particularly evident when ovarian endometriomas are absent and endometriosis causes adhesions and small nodules in the pelvic organs, which are difficult, if not impossible, to detect by ultrasound. It has been reported that peritoneal disease and adhesions are more common than ovarian disease . Therefore, in women who are infertile or have chronic pelvic pain, and in the absence of ovarian endometriomas, it is important to look for sonographic signs of adhesions. Only a few studies have attempted to assess the ability of transvaginal sonographic examination to detect the presence of pelvic adhesions in women with pelvic endometriosis, and to assess their severity .
Normally, the uterus and ovaries are mobile and do not adhere to the surrounding tissues by palpation with the probe, abdominal palpation with the hand, or both. Movement of these organs can be seen on ultrasound (sliding sign). Usually, palpation with the probe, or abdominal palpation with the hand, can cause the ovaries or the uterus to adhere to adjacent structures (e.g. broad ligament, pouch of Douglas (POD), bladder, rectum, and parietal peritoneum). In this case, adhesions can be suspected. Sometimes, in the presence of pelvic fluid, fine septa (adhesions) can be seen between the ovary, the endometrioma, the uterus, or the peritoneum of the POD . Endometrioma are usually fixed posteriorly to the uterus, in the POD. The cause of this, especially in cases of bilateral endometrioma, is that both ovaries are fixed posteriorly to the uterus and have adhered to the controlateral ovary (kissing ovaries) ( Fig. 5 )
To assess stages of the disease in the pelvis, the revised American Fertility Society classification for endometriosis includes the presence and extension of adhesions, endometrioma size, and POD obliteration. Deep endometriotic lesions are not included in this classification.
Recently, preoperative diagnosis of partial or complete obliteration of the POD has been described . The POD is examined using real-time ultrasound imaging to determine the presence or absence of POD obliteration using the sliding sign. To assess the sliding sign, gentle pressure is placed against the cervix with the transvaginal probe to establish whether the anterior rectum glides freely across the posterior aspect of the cervix (posterior cervical region) and posterior vaginal wall.
A number of studies have been conducted on the accuracy of transvaginal sonography for the diagnosis of ovarian adhesions. Classification of the severity of ovarian adhesions as either minimal, moderate or severe, in accordance with the rAFS classification, is rare . Okaro et al. found that preoperative transvaginal sonographic ‘soft markers’ (i.e. site-specific tenderness and reduced ovarian mobility) and ‘hard markers’ (i.e. endometrioma, hydrosalpinx) in women with a history of chronic pelvic pain correlated with the presence or absence of endometriosis and adhesions at laparoscopy. Preoperative transvaginal and transrectal ultrasound have also been used to predict Stage 3 and 4 endometriosis (including pelvic adhesions) at laparoscopy, with a sensitivity and specificity of 86% and 82%, respectively, for Stage 3 and 76% and 91%, respectively, for Stage 4 disease . Guerriero et al. used a technique of applying pressure between the uterus and ovary, and found that a combination of three features are suggestive of ovarian adhesions: blurring of the ovarian margin; the inability to mobilise the ovary on palpation (fixation); and an increased distance from the probe. Sensitivity and specificity of 89% and 90%, respectively, were reported for fixation of the ovaries to the uterus.
The real-time preoperative dynamic transvaginal ultrasound examination of POD obliteration, using the sliding sign technique, seems to be useful in identifying women at increased risk for bowel endometriosis. Hudelist et al. reported that a negative sliding sign on transvaginal sonography predicted DIE of rectum, with a sensitivity of 85%, specificity of 96%, and an accuracy of 93.1%. Reid et al. reported a sensitivity and specificity of 83.3% and 97.1%, respectively, for prediction of POD obliteration.
Magnetic resonance imaging evaluation
Adhesions can be problematic in the evaluation of endometriosis. At MRI, adhesions may sometimes be identified as spiculated low-signal-intensity stranding on T1- and T2- weighted images with a different thickness. Often, only indirect signs of adhesions are present. These include angulation of bowel loop, skip of bowel diameter, elevation of the posterior vaginal fornix, posterior displacement of the uterus, ovaries, or both, loss of fat planes between the structures, hidrosalpinx, and loculated fluid collection. Kataoka et al. reported a mean sensitivity of 77.8%, a mean specificity of 50.0%, and a mean accuracy of 76.3% for the detection of adhesions.
The use of MRI in the evaluation of endometriosis may, therefore, be difficult, and will require experience and specific training in pelvic imaging. The distortion of the structures and the hyperperistaltism of the bowel can cause diagnostic problems in visualising adhesions during MRI.
Deep infiltrating endometriosis
Diagnostic imaging and implications for the treatment of endometriosis
Deep infiltrating endometriosis is the most severe form of endometriosis. It is associated with infertility or pain symptoms, including chronic pelvic pain, dysmenorrhoea, dyspareunia, dysuria, and dyschezia . A wide spectrum of symptom severity exists, and the stage of endometriosis at laparoscopy is poorly correlated with the extent and severity of pain, often resulting in misdiagnosis or delay in diagnosis . This is the case with DIE, as symptoms are not specific . Bimanual pelvic–gynaecologic examination may suggest the presence of DIE by the identification of tender nodules and fibrosis in the cul de sac, but it has poor accuracy in determining the extent of disease . The current gold standard for a definitive diagnosis of endometriosis remains surgical evaluation with histological confirmation, even if deep retroperitoneal localisations have been missed on laparoscopy.
Laparoscopy, in the case of advanced extension of DIE, is a difficult procedure, with a high rate of complications. Therefore, medical treatment is the first choice, and surgery is only recommended in the presence of severe symptoms.
Knowledge before surgery of the anatomical position, size, number of DIE nodules, depth of infiltration of the nodules, and degree of stenosis of the bowel lumen, can help in planning the surgical procedure, in the provision of appropriate counselling to women who undergo the procedure, and in the choice of the right surgical team. For the surgical treatment of DIE, this will include a gynaecologic endoscopic surgeon with particular skills in DIE resection, a urologist and colorectal surgeon depending on the lesions site, or both. In the case of posterior DIE, when the recto-sigma is infiltrated by endometriotic tissue, the bowel is so retracted that even the upper segments can adhere to the posterior wall of the uterus, with complete disruption of normal anatomy. It is, therefore, difficult to distinguish between the rectum and sigma. From a surgical point of view, it is important that diagnostic imaging determinates the lowest limit of the nodule on the bowel wall, as the lower rectal lesions are more difficult to remove surgically by shaving or segmental resection, and have a higher complication rate.
Infiltration of the mucosal layer does not determine whether or not segmentary resection should be carried out; this decision more likely depends on the diameters of infiltrating tissue and the lumen stenosis it causes .
A systematic evaluation of the urinary tract in women with endometriosis is recommended because the prevalence of endometriotic lesions in the urinary tract may be underestimated . Endometriosis of the ureter usually stems from endometriosis of the pelvic foci and ovarian endometriosis . Extrinsic and intrinsic endometriosis are involved in the ureters: extrinsic represents 75–80% of cases, and is defined as the presence of endometrial tissue in the outer adventitia of the ureter. This occurs as a nodule encasing the ureter; intrinsic endometriosis represents 20–25% of cases, and is defined as the presence of endometrial tissue in the mucosal, muscular layer of the ureter, or both. Diagnostic imaging may show direct signs (e.g. a nodule or mass in the ureter along its course, and dilatation of the pelvic ureteral tract), or an indirect (e.g. ureteropelvic hydronephrosis superior to the suspected lesion). In the case of extrinsic compression, ureterolysis can be carried out, whereas a ureteral segmental resection and re-anastomosis is indicated in cases of intrinsic localisation of the disease. Therefore, an accurate evaluation of the urinary tract with computed tomography or MRI urography is mandatory if suspected ureteral involvement is found on transvaginal sonography.
Endometriosis is a chronic disease, and medical treatment, often combined with surgery, is the treatment of choice. Fedele et al. showed that, in women who had previously undergone conservative surgery for endometriosis without excision of deep lesions further treated with levonorgestrel intrauterine device (LNG-IUD), dysmenorrhoea, which had been moderate or severe in all cases, during treatment were absent. Other medical options, such as vaginal danazol (200 mg/day) were also tested on dysmenorrhoea and dyspareunia after surgery for DIE, showing a consistent and significant improvement in painful symptoms . In a recent study of estroprogestin therapy, Mabrouk et al. reported that combined oral contraceptive therapy may have a role to play in restraining the progression of dysmenorrhoea and dyspareunia, and the growth of deep endometriotic nodules. It has also been shown recently that medical treatment performed significantly better in relieving pain in women without DIE compared with women with recto-vaginal lesions .
It seems, therefore, that as much detail as possible about the spread and localisation of the disease are needed by the surgeon and clinician responsible for medical treatment. The careful evaluation of clinical and diagnostic imaging findings gives clinicians the opportunity to decide the best surgical approach, the possible need to involve surgical specialists other than a gynaecologic surgeon (e.g. colorectal surgeon or urologist), so that management of the disease can be tailored correctly, and patients can be informed of the extent of their disease and the therapeutic options available.
Ultrasound evaluation of deep infiltrating endometriosis
Transvaginal sonography can evaluate all potential locations of DIE in the anterior (bladder) or posterior–lateral compartment. These include the rectovaginal septum, uterosacral ligaments, torus uterinum (i.e. tissue behind the cervix in the mid-sagittal plane between the uterosacral ligaments), posterior vaginal fornix, rectum and rectosigmoid junction, and parametria and ureteral involvement.
Endometriotic nodules of the bladder and the rectum can be evaluated with a transvaginal probe and, if necessary, a transrectal examination with the same convex probe can be carried out. During the transrectal examination, a fluid contrast medium can be inserted into the vagina ( Fig. 6 ) to better visualise the recto-vaginal septum.
