The use of imaging in endometriosis

Endometriosis is a complex and often painful condition characterised by the presence of endometrial tissue outside the uterus . This may lead to inflammation, scarring and symptoms such as pelvic pain and infertility. It may manifest itself as superficial or deep disease as well as ovarian disease with the presence of endometriomas . This study came to fruition in order to emphasise the importance of imaging with respect to the diagnosis of endometriosis. Whereas previously a surgical approach was the gold standard, imaging has now become the benchmark for diagnosis . The aim of this paper is to highlight the importance of imaging in endometriosis by reviewing literature on various databases such as PubMed and combining the most salient and relevant points . The goal is to underscore the previous points even further . This literature review revealed that techniques such as ultrasound, magnetic resonance imaging (MRI) and computed tomography (CT) are utilised to visualise endometrial lesions, cysts and associated pelvic anatomy variations . Ultrasound, in particular transvaginal, is often the first-line imaging tool primarily because of its accessibility and non-invasiveness . MRI however is considered the gold standard for evaluating deep infiltrating endometriosis and is able to provide a detailed image of soft tissue structures . It is therefore the mainstay investigation prior to management planning and surgical intervention . In conclusion, the use of imaging does not simply aid with management planning however, is able to assist in monitoring disease progression and response to treatment

Endometriosis, imaging, MRI, ultrasound

Endometriosis 1s a gynecological disorder characterised by the presence and growth of tissue which when viewed under a microscope, is similar to endometrial tissue, outside of the uterus . The prime age of diagnosis is between the ages of 30 and 45 however lesions may occur in 1-20% of all women, most often asymptomatically . These lesions can be found throughout the pelvis, most notably in the uterosacral ligaments and surrounding the ovaries where it may form endometriomas or "chocolate cysts" . It may also occasionally affect abdominal wound scars, the vagina, bladder, rectum and sometimes even the lungs. Endometriosis, like normal endometrium within the uterus, responds to oestrogen. This explains why it is known to regress during the menopause as well as pregnancy, and is seen to have fluctuating symptomatology during the menstrual cycle. In severe cases, endometriosis has been seen to cause what is known as a "frozen pelvis" secondary to 9B progressive fibrosis and the formation of adhesions . Clinically, a patient may present in a number of various ways ranging from cyclical chronic pelvic pain to dysmenorrhea prior to the onset of menstruation, deep dyspareunia, infertility as well as dyschezia. More acute cases may be characterised by sudden onset abdominal pain secondary to rupture or torsion of an endometrioma. Vaginal examination may reveal thickening in the adnexa, an immobile or retroverted uterus , or may also be completely normal! Whereby the previous gold standard to diagnosis was via laparoscopy, imaging has slowly taken over mainly because it is less invasive and patients are therefore more likely to comply, however also because of its sensitivity with respect to diagnosing endometriotic lesions. Literature Review Moradi et al wrote that there is an average delay of 7-12 years in the diagnosis of endometriosis (1 ). This delay in diagnosis results in delays of interventions that relieve pain and discomfort associated with this condition, which in some women can be so severe causing them to harm themselves. For this reason, it is imperative to invest in women 's health since delays in diagnosis

in significant psychological burden (2). NICE guidelines recommends ultrasound, which is usually trans-vaginal or trans-abdominal as the primary imaging modality, however, transvaginal ultrasound is preferred. Other guidelines such as ESHRE also include MRI as being one of the primary imaging modalities (3). Patients tend to prefer ultrasound due to its quick and easy process, as well as being relatively cheap, however the use and accuracy of results depends greatly on the operator 's skill and experience, as well as the severity of the disease. Ultrasound Ovarian endometriomas are arguably the most common forms of endometriosis found on ultrasound . It is generally described as unilocular or multilocular cystic lesions with a ground-glass appearance measuring [X] x [Y] x [Z] with no internal vascularity noted on Doppler imaging . Internal vascularity would prompt investigations for more sinister causes for the ovarian mass. Additional findings may include finding free fluid in the pouch of Douglas as well as tenderness on transvaginal probe pressure correlating with the lesion location . The ultrasound operator may also find endometrial glands within the myometrium, meaning that there is co-existing adenomyosis . Adenomyosis and endometriosis are closely related however may be distinguished since endometriosis is found outside the uterus while adenomyosis is found within the myometrium. To assess the extremity of ovarian endometriosis, the operator may elicit the "sliding sign" using the application of pressure to the trans-vaginal probe to measure the degree of mobility of the pelvic structures . A positive sliding sign is normal; meaning that the anterior rectum glides freely over the posterior uterus . A negative sliding sign is a bad prognostic indicator since it denotes the presence of deep infiltrating endometriosis, meaning that there is involvement of uterosacral ligaments, bladder, bowel, vagina and any part of the peritoneum. MRI With MRI, soft tissue can be seen in much greater detail, than with ultrasound, thus it is good to distinguish lesions when the diagnosis is in doubt. However, patients may be reluctant since there is a need to be in a closed space for a long period of time. It is important to mention that even though high-resolution pictures are obtained through MRI, a diagnosis of endometriosis cannot be ruled out if there are no findings on imaging, and further investigations are required when there is a high clinical index of suspicion . MRI uses T 1 and T2 99 weighted images, therefore it is important to distinguish that endometriosis is hyperintense on Tl images and hypointense on T2 images. There will also be shading signs showing layering of blood within the lesion. MRI is useful when a diagnosis of endometriosis is made on ultrasound, but the degree of disease needs to be further quantified . An example of advanced disease seen on MRI is distorted pelvic anatomy due to adhesions and fibrosis associated with deep infiltrating endometriosis . Despite the many signs and clues seen on ultrasound and MRI which help us in our diagnosis, smaller and more superficial lesions are usually missed ( 4), thus, this is where laparoscopy starts to play an important role in the imaging­ negative patient with a high index of suspicion. Unfortunately, a clinical exam is of little use in most cases of endometriosis since only about half of the larger lesions are thought to be palpable . One main disadvantage of imaging is that in some cases, it is unable to differentiate between ovarian cancer and ovarian endometriosis . In addition, both conditions constitute a rise in Ca125 which does not help in differentiating the two diagnoses . This is especially an issue in older postmenopausal women, who might have had endometriosis for years but never sought help, or got a proper diagnosis, and thus further warrants surgical exploration via laparoscopy (5). Koninckx et al. describe the inaccuracy of imaging via calculations alleging that a test with 99% sensitivity and specificity still results in 50% false positive results. They also mention the possible integration of artificial intelligence in the future to strengthen the reliability of imaging techniques and slowly start moving away from surgical techniques. When there is uncertainty, surgical options can be particularly damaging especially to the younger patient. This is because endometriosis tends to be a recurring condition, thus adhesion formation from surgery may cause recurrence of endometrial lesions, possibly even in the adhesion or surgical scar! It also poses a threat to the young female's fertility and affects family planning (5). For this reason, many doctors and patients take the collective decision to commence medical therapy without a definite diagnosis, thus contributing to the delay in diagnosis as explained earlier by Moradi et al. PET-CT Positron em1ss1on tomography- computed tomography (PET-CT) has a wide range of use in oncology, but it is being applied outside of the oncological field in various novel studies overseas to assess its ability to aid in other possibly benign diagnoses, such as that of endometriosis . Since endometriosis may mimic ovarian cancer, it can be applied to identify endometrial lesions and endometriomas (6). It is a promising diagnostic technique smce PET involves mJection of radiolabeled tracers intravenously to highlight parts of the body that take up that specific tracer, for example, in areas that are more metabolically active. There are many tracers that can be used for this purpose . Initially, studies used F­ fluorodeoxyglucose as the radiolabeled substance­ which showed promising results (7), however studies are shifting their focus towards the assessment of F-flouroestradiol and F­ flourofuranylnorprogesterone as well as the integration of PET-CT with other imaging modalities to improve early-stage diagnoses (8). MRE Magnetic resonance elastography (MRE) is used to add an extra dimension to the image formed to determine the tissue's character (mechanical and physical properties such as stiffness and viscosity). It allows the surgeon to know the lesion's characteristics beforehand to be better prepared about what is most likely to be found during surgery, since the lesion's characteristics and 100 composition influence decisions for removal (8). MRE also overcomes MRI's limitation of not being able to identify the difference between ovarian cancer and ovarian endometriomas in some cases. The downsides of this technique are that it is very expensive, requires investigation for a long time like MRI, and it is not yet available in Malta.

Patients suffering from this chronic, relapsing condition experience reduced quality of life, time off work and overall increased suffering . It is our duty as medical professionals to enhance their quality of life, make sure that our patients feel heard, listen to their concerns and follow them up on any issues they might have . With the advancements in modern medicine, as well as the increase in awareness of the condition, more and more women are being diagnosed and treated accordingly. As physicians, we must always take pelvic and menstrual pain seriously , as they may be dismissed as normal, therefore instead of fixing the problem, we would be contributing to the worsening of the problem . In addition, we must also be aware to find and treat the problem, with the least invasive procedures possible . A management plan in line with the lifestyle and wants of the patient should be devised keeping the patient informed, included, and at the center of all decisions taken . Declarations None to declare .

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