The gastrointestinal tract is the most common site of extrapelvic endometriosis, affecting 5–15% of women with pelvic endometriosis [1, 2]. Among women with intestinal endometriosis, rectum and sigmoid colon are the most common involved areas (75–90%). Other parts of the bowel commonly affected are the distal ileum (2–16%), and appendix (3–18%) . Only the serosa and the muscularis propria are usually involved, while the mucosa is very rarely affected .
Intestinal endometriosis may present with rectal bleeding, bowel obstruction and rarely with perforation or malignant transformation [5, 6]. Symptoms can be cyclical in about 40% of patients, can vary depending on the site and include crampy abdominal pain, distention, diarrhea, constipation, tenesmus and hematochezia . The classic triad of dysmenorrhea, dyspareunia and infertility, as a result of concomitant pelvic disease, may also exist. We should, however notice, that the cyclical character of symptoms does not exclusively appear in endometriosis. It is well established that clinical manifestations in inflammatory bowel disease and irritable bowel syndrome may aggravate during the menses [7, 8].
The clinical, radiological and endoscopic picture may be confused with neoplasms, ischemic colitis, inflammatory bowel disease, post radiation colitis, diverticular disease and infection. Although endoscopic diagnosis of colonic endometriosis has been reported  usually the endoscopic appearance, even if there is mucosal involvement, is not diagnostic. Biopsies obtained endoscopically usually yield insufficient tissue for a definite pathologic diagnosis . Moreover, endometriotic deposits can induce secondary mucosal changes, which mimic findings of other diseases such as inflammatory bowel disease, ischemic colitis, or even a neoplasm [11, 12]. The CT scan or barium enema usually demonstrate an extrinsic bowel compression, stenosis or filling defect. MRI seems to be the most sensitive imaging technique for intestinal endometriosis . Yet, the gold standard for the diagnosis is laparoscopy or laparotomy.
Treatment options include surgery or hormonal manipulations, depending on patient's age and desire to maintain fertility and also on the severity and complications of the disease . Recently, laparoscopic treatment of colorectal endometriosis, even in advanced stages, has been proven feasible and effective in nearly all patients . The medications used in the treatment of endometriosis are danazol, high dose progestins and GnRH agonists with almost equivalent efficacy . The choice of which to use is based on side effects and costs. Danazol and GnRH agonists are of equivalent cost, but GnRH agonists are usually better tolerated. In our case, although high dose progestins could have been used, after discussion with the patient she chose to receive GnRH agonists.
Our patient represents a case of symptomatic gastrointestinal endometriosis with mucosal involvement, without a previous history of pelvic endometriosis. The symptoms of abdominal pain, constipation and hematochezia, the presence of anemia in combination with the radiologic and endoscopic findings were suggestive of a neoplasm. On the other hand the patient's long history of dysmenorrhea, the normal levels of CEA and CA19-9, and the absence of neoplastic infiltration in all biopsy specimens were against the diagnosis of colon cancer. Furthermore, the ovarian chocolate cysts showed by the pelvic ultrasound and the histologic evidence, obtained from the second colonoscopy, directed us towards the diagnosis of intestinal endometriosis that was finally confirmed during the laparoscopy. Moreover, this patient had elevated serum levels of CA-125, which has been established as a useful marker for determining the severity of endometriosis [17, 18]. The colonic mucosal involvement in this case could be explained by the invasion of endometrial cells through the bowel wall. Lymphatic or vascular metastasis could explain rare cases of endometriosis located in pleura, umbilicus, muscle, brain, vagina, cervix and retroperitoneal space [1, 2].
In conclusion, intestinal endometriosis is often a diagnostic challenge mimicking a broad spectrum of diseases and should be considered in any young woman with symptoms from the lower gastrointestinal tract.