An endometriotic nodule infiltrating the intestinal wall to the submucosal layer. (a) lumen reduction, (b) fibrotic core
20.2 Incidence and Epidemiology
Endometriosis affects 6–10 % of all women of childbearing age. Endometriosis has estimated annual costs of approximately US $12,400 per woman (approximately € 11,000), comprising one-third of direct health care costs with two-thirds attributed to loss of productivity. Based on a review of cost estimates, the annual costs of endometriosis attained $22 billion in 2002 in the United States. These costs are considerably higher than those related to Crohn’s disease or to migraine. Decreased quality of life is the most important predictor of direct health care and total costs.
Endometriosis is predominantly found in women of reproductive age of all ethnic and social groups and generally associated with pelvic pain and infertility. Infertility problems can impact on the physical, mental and social well being of a woman and can have a profound effect on her life, including the ability to finish an education, maintain a career, or to create a family. For these reasons the European Union Written Declaration has recognized endometriosis as a disease with an important economic impact on the community demonstrating a significant association with health costs related to diagnostic delays and therapeutic expenses including surgery, drugs, and assisted reproductive technologies (ART) .
DIE occurs in up to 30–40 % of patients with endometriosis whereas intestinal endometriosis has been estimated to occur in 8–12 % of these women . Deep gastrointestinal involvement in endometriosis is characterised by fibrous, retractile thickening of the intestinal wall. The most common location is the upper rectum, in contiguity with a lesion of the torus uterinus since its prevalence increases with the severity of pelvic involvement reaching 50 % in stage IV of the American Fertility Society (AFS). Chapron et al.  reported the anatomical distribution of DIE lesions in the digestive tract in 426 consecutive patients who underwent complete surgical excision of DIE: recto-sigmoid junction and rectum in 65.7 %, sigmoid in 17.4 %, appendix in 6.4 %, small bowel in 4.7 %, cecum and ileocecal junction in 4.1 %, and omentum in 1.7 %. Furthermore rectal lesions are associated with a second intestinal lesion in 54.6 % of cases .
The revised American Society for Reproductive Medicine (rASRM) score  is currently the best-known classification of endometriosis and is the one most widely used throughout the world (Fig. 20.2).
The revised American Society for Reproductive Medicine (rASRM) score for endometriosis
It is relatively easy to use, but it does not take into account the involvement of retroperitoneal structures with deeply infiltrating endometriosis. For this reason, the Enzian classification was developed as a supplement to the rASRM score, in order to provide a morphologically descriptive classification of deeply infiltrating endometriosis (Fig. 20.3) .
The Enzian classification
The diagnosis of endometriosis is histological and it follows a surgical procedure in most cases.
Preoperative diagnosis is sometimes very difficult because symptoms are common and mimic others frequent pathology (i.e. irritable bowel syndrome, appendicitis, adhesions, etc.). Opinion leaders continue to support the need of a reliable non-invasive test to distinguish between the pain endometriosis and other causes since there is a significant delay in the diagnosis of this pathology: recent studies report an overall diagnostic delay of 10 years in Germany and Austria, 8 years in the UK and Spain, 7 years in Norway, 7–10 years in Italy and 4–5 years in Ireland and Belgium . Ballard et al.  distinguished between delays at the patient level and delays at the medical level. This is generally because both women and family doctors tend to consider this type of pain as normal menstrual discomfort and neglect the need for treatment.
In endometriosis typical symptoms include dysmenorrhoea, deep dyspareunia (pain on deep penetration), dyschezia (pelvic pain with defecation), dysuria (pain with micturition) although the association between endometriosis stage and severity of pelvic symptoms has been demonstrated to be marginal and inconsistent . Symptoms are usually synchronous with menstruation.
Pelvic pain is an important issue in the health care of women contributing to 10 % of all outpatient gynaecological visits, 40 % of laparoscopies and is the indication for 10–15 % of hysterectomies . The existence of a relationship between chronic pelvic pain symptoms and endometriosis is widely accepted, but various other painful pelvic symptoms are also normally present in the general population.
Women presenting with rectal endometriosis are more likely to report an increase in intensity and duration of dysmenorrhoea, while deep dyspareunia appeared to be more severe in women with superficial endometriosis. Women presenting with rectal endometriosis are more likely to present cyclic defecation pain (67.9 %), cyclic constipation (54.7 %) and a significantly longer stool evacuation time, although these complaints are also frequent in women with Stage 1 endometriosis and in women with deep endometriosis without digestive involvement. No independent clinical factor has been found to be related to infiltration of the rectum by deep endometriosis and few women with rectal endometriosis present with rectal stenosis, however these women are significantly more likely to report constipation, defecation pain, appetite disorders, longer evacuation time and increased stool consistency without laxatives. Various digestive symptoms seem to be more related to cyclic inflammation than to rectal infiltration by the nodule, as they occur in women free of rectal involvement .
Ileocecal endometriosis may mimic appendicitis while other intestinal locations may cause bloating and discomfort related to narrowing, however intestinal occlusion is exceptional.
20.4.2 Physical Examination
220.127.116.11 The Gynecologist
Patients suspected to have endometriosis should ideally first attend a gynaecologist with a specialist interest. A finding of pelvic tenderness, a fixed retroverted uterus, tender uterosacral ligaments or enlarged ovaries leads to a potential diagnosis of DIE. The diagnosis is more certain if deeply infiltrating nodules are found on the uterosacral ligaments or in the pouch of Douglas, and/or visible lesions are seen in the vagina or on the cervix, however, physical examination is often inconclusive because lesions, most lesions are inaccessible to digital pelvic examination and colposcopy.
18.104.22.168 The Colorectal Surgeon
Since medical management of bowel endometriosis is currently emperic, the expectant management should be carefully balanced with the grade of symptoms by the specialist gynecologist who has the role of referring patients to the colorectal surgeon (CRS) when severe intestinal DIE is suspected.
Pelvic nodules are detected either through direct palpation or by causing pelvic pain on palpation of the anterior rectal wall. Bimanual digital exploration allows evaluation of involvement of the rectovaginal septum. The integrity and function of the anal sphincters is also checked during the examination: this is extremely important should a low rectal resection become necessary.
The clinical exam is completed by a rigid proctoscopy. Visualization of the mucosa allows diagnosis of potential causes of rectal bleeding. Rectal distention by air insufflation may trigger pelvic pain, while palpation of the anterior rectal wall with the proctoscope helps to localize the level of involvement by measuring its distance from the anus.
The surgeon has to confirm the clinical diagnosis of DIE through an appropriate patient history and clinical examination including a proctoscopy; subsequently the CRS has to evaluate a presumable level of intestinal involvement in order to plan the appropriate type of procedure especially when the rectum is affected. Only at this stage the surgeon is able to discuss the case with the patient providing detailed information about the type of surgery and its possible related complications for achieving an appropriated consent.
Transvaginal sonography (TVS) performed after bowel preparation should be the first-line imaging examination and is the best imaging modality for identifying intestinal lesions, determining the depth of bowel wall invasion and the circumference of involved bowel. This method allows dynamic evaluation from the anal verge to the sigmoid with high spatial resolution and minimal patient discomfort. The proximity between the transducer and the targeted structure provides superior contrast resolution, which is important for visualizing small and laterally located lesions. A useful tool for preoperative mapping of endometriosis by TVS (the Endometriosis Surgical-Ultrasonographic System) has recently been developed with the specific aim of creating a common language so that physicians who are dedicated to the diagnosis and treatment of patients with severe endometriosis can accurately share clinical data. It gives clinicians the opportunity to decide on the best surgical approach, to evaluate the potential need to involve other surgical specialists (general surgeon or urologist), to establish a tailored management of the disease, and to properly inform patients of the extent of the disease and therapeutic options .
TVS is as accurate as transrectal US for diagnosing intestinal lesions and identifying the bowel layers affected, and it yields better results than magnetic resonance (MR) imaging for the assessment of deeply infiltrating endometrial implants in other pelvic locations, especially small (<1.5-cm-diameter) lesions of the uterosacral ligament and bladder . MR imaging is an excellent method for identifying old hemorrhagic content that characterizes endometriomas and for mapping multiple DIE implants, given its large field of view, multiplanar capabilities, and outstanding contrast resolution. Extensive pelvic adhesions and ureteral involvement are two important indications for MR imaging . In DIE lesions are mostly hypoechoic in comparison with the myometrium: on MR images, they have signal intensity similar to that of smooth muscle, with low signal intensity on T2-weighted images, intermediate signal intensity on T1-weighted images, and minimal enhancement after the intravenous injection of contrast material. Cystic areas may be present, with or without hemorrhagic content.
MR imaging is less sensitive than endorectal ultrasound (ERUS) for DIE in the rectal wall but is more specific, up to 95 % . The MR sensitivity may be improved with by use of endocavity probes  or with intra-rectal contrast  (Fig. 20.4). Since intestinal involvement is often associated with multifocal disease, MR imaging is essential for complete staging of disease. ERUS is the standard technique to evaluate DIE of the rectal muscular layer with 97 % sensibility and 85 % specificity . TVS may have similar sensitivity and specificity for rectal endometriosis with less patient discomfort and in expert hands could replace ERUS . CT scan is of less value and is used when MRI is impracticable or for specific sites (e.g. urethral involvement) .
Double contrast pelvic MRI showing the presence and the grade of rectal infiltration by a DIE nodule
Management of patients with endometriosis is multidisciplinary, ideally performed in specialist referral centres . It is very important to identify the objectives and the expectations of the woman at this stage. The planned treatment must take into account any desire for pregnancy, the presence of other infertility associated factors, multifocal lesions and heterogeneity of the disease. Endometriosis is not a malignant condition and radical surgery can have major complications (intestinal, urinary, vascular), therefore the patient must be involved in the decision on her own ‘customised’ treatment.
20.5.1 Medical Treatment
Endometriosis is an estrogen-dependent disease that tends to disappear with menopause. Medical treatments, based on the concept that the eutopic and ectopic endometrium respond similarly to sex hormones, are hormonal and based on blocking ovarian function. Several therapeutic classes are available (combined oral oestroprogestative, GnRH analogues etc.) and offer free intervals from pain causing atrophy of endometriotic implants. Their effectiveness is similar, so the choice is based on cost and balance of side effects ; in this context, combined oral contraception is often used initially . In infertile patients, in vitro fertilization may be considered either before or following surgery for DIE .
Bowel surgery should only proceed on the basis of shared decision-making after thorough consideration of risks versus benefits, ideally following multi-disciplinary consultations and full information to the patient who shares the final decision. The role of a purely diagnostic laparoscopy has been questioned and, ideally, there should always be the option of continuing to surgical removal of endometriosis, within the limitations of the surgeon’s expertise. It is also important, particularly in cases of more severe endometriosis, that surgeons consider the option of limiting surgical excision at an initial operation in order to refer to a surgeon better equipped to deal with endometriosis, as a single radical surgery has been shown to deliver the greatest benefit . Surgery in the follicular phase of the menstrual cycle avoids the presence of a hemorrhagic corpus luteum and one study suggested an increased recurrence rate for surgery undertaken in the luteal phase, possibly due to re-implantation through retrograde loss of endometrial tissue at subsequent menses while the sites of surgically removed lesions are healing .
The experience of the surgeon is critical in a decision for local removal of a nodule infiltrating the intestinal wall as incomplete resection may not relieve symptoms , while radical intervention increases the risk of major complications such as ureteric and rectal injuries.
First operations tend to produce a better response than subsequent surgical procedures, with pain improvements at 6 months in the region of 83 % for first excisional procedures versus 53 % for second procedures [22, 25]. Excessive numbers of repeated laparoscopic procedures should therefore be avoided.
The surgical options for treating DIE in the bowel include peeling, disc excision or segmental excision and re-anastomosis. The peeling technique has the advantage that it avoids opening the bowel but it carries a risk of incomplete excision  and bowel microperforation that may not be recognized potentially leading to post-operative pelvic peritonitis. The hydropneumatic test (visualization of bubbles in the pelvis filled with water after air insufflation of the rectum) may be used to identify microperforation but is not always diagnostic and resection may be considered as safer in some cases.
Nezhat et al.  were the first to report a case series of eight patients treated with laparoscopic disk excision for endometriosis affecting the anterior colonic wall. Anterior rectal wall excision using a circular stapler was first proposed by Gordon et al.  to avoid the risks of a low extraperitoneal anastomosis in cases of nodular endometriosis invading the rectovaginal septum. Others [28, 29] have confirmed the feasibility of laparoscopic full thickness disk excision of endometriosis. The upper limit of the size of the lesion that can be removed is questionable and subjective because it is assessed visually, but it is generally agreed that lesions excised in this way should not exceed 2–3 cm in diameter and should not involve more than one-half of the circumference of the rectum. Disk excision may result in incomplete excision as endometriosis may infiltrate the large bowel wall preferentially along the myenteric plexus up to 3 cm from the palpated lesion .
The decision to carry out segmental bowel resection should be individualized. A decision to resect is supported by the depth of nodular infiltration, size and multicentricity of nodules, and the risk of incomplete excision . Currently, only a complete surgical resection based on removal of all endometriosis lesions is considered adequate to controls the symptoms [32, 33] and prevent recurrence [34, 35]. The issue of how to treat lymph node involvement is unresolved as the clinical importance of lymph node involvement is not yet clarified .
The variety and depth of infiltration into other organs is testified by the number of previous surgical interventions, up to 82 % in the series reported by Dousset et al.  and by the number of synchronous procedures on the reproductive and urinary organs. Ileocolic locations should be searched carefully intraoperatively because preoperative imaging fails to identify these in over 50 % of cases. These may be treated by appendectomy, caecal, ileal or ileocaecal resection depending on the location.
Patients with DIE and rectal involvement may require a sub-total or total proctectomy depending on the level of lesion in relation to the anal sphincter with subsequent low or ultralow coloanal anastomosis. The resection may be extended “en block” to posterior vaginal cul-de-sac, uterosacral ligaments or sigmoid when involved; this is extensive surgery and requires in most cases a protective temporary ileostomy to prevent the sequele of an anastomotic leak or a rectovaginal fistula.
The ureters should always be identified and followed distally to ensure the absence of infiltration by endometriotic nodule. Extrinsic involvement is treated with a “decompression” protected by a double J stent. Intrinsic ureteral involvement is treated by resection followed by ureteral-bladder reimplantation or nephrectomy in case of chronic ureterohydronephrosis. During mobilization, the hypogastric plexus should be identified and preserved to avoid sexual or urinary functional alteration such as peripheral neurogenic bladder. This may be achieved by preserving the superior haemorrhoidal artery. Post operative neurogenic bladder is more common following proctectomy with coloanal anastomosis, total hysterectomy and presence of up to four DIE pelvic locations .