Endometriosis is a disease characterized by the presence of endometrial glands and stroma outside the uterine cavity. A chronic inflammatory reaction induces scar tissue and adhesion formation that may distort a woman’s pelvic anatomy and cause disabling pelvic pain and intractable infertility. Although the cause of this disease is unknown, the most likely explanation involves the implantation of viable endometrial cells from retrograde menstruation through the fallopian tubes. Endometriosis has been estimated to affect up to 15% of all women of reproductive age. Twenty percent of women with endometriosis will have intestinal involvement, and the majority of these cases involve the rectosigmoid region. Colon and rectal surgeons most commonly become involved in the management of patients with intestinal endometriosis as a combined procedure with a gynecologist treating the other pelvic implants, or in the management of an endometrioma masquerading as a neoplastic or inflammatory lesion.
Pain, the most common symptom of endometriosis, affects up to 80% of patients who are subsequently diagnosed with the disease. Dysmenorrhea is the most common gynecologic symptom. Intestinal symptoms of patients with deep infiltrating endometriosis are pelvic pain upon defecation (which can be cyclical), dyspareunia, and rectal bleeding. In women undergoing laparoscopy for pelvic pain, endometriosis is discovered in 30% to 50% of cases. Although the total lesion volume often equates to the degree of pain, some women with extensive endometriosis experience little or no pain. Symptoms appear to be related to the depth of penetration, the type of lesion, and its location. Implants involving the uterosacral ligaments and rectovaginal septum are most often implicated in patients with pelvic pain. This pain is typically most intense just prior to the onset of menstruation. It is often associated with back pain, dyschezia, and levator muscle spasm and is more severe with advanced stages of endometriosis. The presence of dyspareunia is often seen with fixation of the pelvic organs, especially in the cul-de-sac of Douglas, the uterosacral ligaments, and the rectovaginal septum.
The exact causal relationship between endometriosis and infertility is also unclear, but the correlation is well established. In women with known endometriosis, the infertility rate is 30% to 50%, and conversely, in infertile women, the incidence of endometriosis is 25% to 50%. Fecundity in normal couples ranges from 0.15 to 0.20 per month and decreases with age, whereas women with endometriosis tend to have a lower monthly fecundity of about 0.02 to 0.1. There is little disagreement that moderate to severe disease with mechanical distortion of the fallopian tubes, ovaries, and peritoneum can potentiate infertility. Pelvic endometriosis and the resulting inflammatory response can produce dense, fibrotic adhesions that may significantly interfere with both the oocyte release from the ovary and the ability of the fallopian tube to pick up and transmit the oocyte to the uterus. In moderate or severe endometriosis, the pregnancy rates after surgical removal of the endometrial implants are 50% and 40%, respectively, compared with only 7% when expectant management is practiced. Treatment of infertile patients with mild endometriosis is more problematic. Infertile women with mild endometriosis did not have any improvement in fertility with either medical or surgical therapy compared with expectant management. Other studies have demonstrated a lower pregnancy per cycle rate in patients with mild endometriosis compared with those who are free of the disease.
Mild cases of endometriosis may not be demonstrable on physical examination. The diagnosis may not be made unless the patient undergoes laparoscopy. Bimanual and rectal examination may reveal nodularity or induration in the utero-sacral ligaments or the cul-de-sac of Douglas. Fixed tender retroversion of the uterus in a patient without previous pelvic surgery raises suspicion for endometriosis. Cyclical pelvic and abdominal pain or bleeding from any location should be investigated for endometriosis. The inguinal canal, previous incisions, umbilicus, and lungs can all potentially harbor endometrial implants.
Endoscopic evaluation of the large bowel is often normal except in severe disease with infiltrating nodular endometrial implants. Colonoscopy is most useful in excluding colon cancer from the differential diagnosis, especially in older patients presenting with a rectosigmoid mass while undergoing hormone replacement therapy. Because the typical lesions in endometriosis begin as serosal nodules, colonoscopic evaluation will generally demonstrate grossly normal appearance of the mucosa. Occasionally, however, significant luminal narrowing may be identified, a result of infiltration of the submucosa, which produces nodularity and distortion of the overlying mucosa. These areas of distorted bowel may produce pain, suggesting the diagnosis of endometriosis.
Rigid proctoscopy is very helpful in predicting the depth of rectosigmoid involvement in patients with severe endometriosis of the cul-de-sac of Douglas. The mucosa is often fixed over areas of submucosal or deep muscular involvement with tethering or puckering and loss of the normal mucosal mobility. In our experience, these mucosal findings have correlated with significant intestinal wall invasion by the endometrial implant and often signal a need for intestinal resection. Our experience has demonstrated that this physical examination finding has a 70% positive predictive value for segmental colonic resection.
Ultrasonography, barium enema, computerized tomography (CT), magnetic resonance imaging (MRI), and immunoscintigraphy have all been used to help diagnose endometriosis. Often these tests are obtained during the evaluation and workup of chronic pelvic pain and/or bleeding from the reproductive tract or colon. Varying utility and sensitivity can be attributed to each modality, and their value is ultimately judged against the diagnostic gold standard, laparoscopy. Laparoscopy, however, can be inconclusive in assessing deep infiltrating disease and cul-de-sac involvement and in correctly predicting intestinal resection. As such, each imaging modality may have a role in future operative planning.
Transvaginal ultrasound provides specificity greater than 90% for ovarian endometriosis. In contrast, pelvic ultrasound is not very sensitive in detecting focal nonovarian endometrial implants. Although the procedure itself can be quite painful to the patient, if it can be tolerated, endorectal ultrasound will detect rectal wall invasion of endometrial implants in the cul-de-sac. Sensitivity and specificity of endorectal ultrasound for preoperative staging of rectal wall involvement by endometriosis have been reported to be as high as 97%, but its usefulness is limited by pain.
CT is the imaging technique used most frequently for the evaluation of abdominal and pelvic pain, mainly because of the availability of CT rather than its utility or sensitivity for this diagnosis. There is no standard CT appearance for a mass caused by endometriosis to clearly differentiate it from pelvic masses due to other causes. CT colonography may change this limitation because it is able to identify luminal alterations of the rectosigmoid colon and obliteration of the cul-de-sac, with sensitivity and specificity approaching 96% and 80%, respectively.
MRI continues to gain an increasing role in the diagnostic workup of endometriosis. Multiplanar capabilities and superior soft tissue contrast are extremely useful in the detection of deeply infiltrating endometriotic implants, even in the setting of an intense desmoplastic response that may result in complete obliteration of the posterior cul-de-sac and fixed retroversion of the uterus. Colorectal involvement is strongly suspected when disappearance of the fat plane between the rectum and the vagina is noted, when the hypointense signal of the anterior bowel wall is lost on T2-weighted images, and when a contrast-enhanced mass involving the bowel wall is noted on T1-weighted images. The sensitivity and specificity of MRI for detecting and adequately evaluating colorectal endometriosis is approximately 78% and 98%, respectively. The ability of 1.5-T MRI to characterize the extent of cul-de-sac obliteration by endometriosis fell short, but the recent introduction of 3-T MRI offers a better space and contrast resolution, which may translate to better detection of cul-de-sac implants and associated bowel involvement.