Endometriosis is a general term for endometrial tissue found outside the uterus and is present in 5 to 15% of women of reproductive age . It has been reported that 12 to 37% of patients with endometriosis have intestinal endometriosis . Ectopic endometrial tissue invades and grows in the intestinal tract, causing bleeding, stenosis, and adhesions. The most common site of this disease is said to be the sigmoid colon or rectum .
Before surgery, intestinal endometriosis was diagnosed in 2 of the 5 patients. Otherwise, it was difficult to diagnose preoperatively. Among the 2 patients, the clarifying symptom of pain was present at the time of menstruation in only 1 patient.
In case 3, non-menstrual CT showed no findings at the terminal ileum, but MRI performed during menstruation showed a mass. Because of the different modalities, it is not possible to conclude based on this report alone, but it was also important to examine the difference between menstrual and non-menstrual images in diagnostic imaging of intestinal endometriosis. Although no reports on menstrual and non-menstrual imaging have been found in previous reports, the accumulation of future cases is considered important. Obtaining a preoperative diagnosis appears to be difficult for patients with a submucosal lesion; however, Oliveira et al. reported that intestinal endometriosis should be considered in the differential diagnosis of patients with submucosal tumors of the colon . If intestinal endometriosis is established as part of the differential diagnosis, a preoperative diagnosis should not be difficult.
D2 dissection was performed for case nos. 1, 2, and 4; because malignancy could not be ruled out preoperatively. Tumors arising from intestinal endometriosis are rare and are collectively referred to as endometriosis-associated intestinal tumor (EAIT) . Malignant transformation can develop in some cases , and metastatic lymph nodes have been observed . Previous reports indicate that 78.7% of endometrial malignancies occur in the ovaries and 21.3% outside the ovaries. Of the latter, the pelvis accounted for 5.7%, the rectovaginal septum 4.3%, the colorectum 4.3%, and the small intestine 0.5% .
There have been reports that endometrial tissue has also been found in regional lymph nodes at the time of the resection of the intestine involved with endometriosis; however, the relationship between lymph nodes containing endometrial lesions and the malignant transformation of endometrial lesions in the intestine has not been clarified, and carcinomas associated with intestinal endometriosis are rare [9, 10]. Some believe that lymphadenectomy is not so effective for endometriosis . If there is no suspicion of a malignant tumor, lymph node dissection is unnecessary, even if the lymph nodes are involved. If malignancy cannot be ruled out, excision of the intestinal tract with lymph node dissection should be considered.
The surgical findings of 1 of our 5 cases did not suggest endometriosis. The surgical findings of surgery for intestinal endometriosis often include advanced pelvic adhesions and fibrosis. These findings are thought to be caused by endometrial tissue, which undergoes fibrosis, and metaplasia of smooth muscle extending throughout the muscular layer to the subserosal layer of the intestinal tract and repeatedly causing bleeding and inflammation along with the menstrual cycle .
Rocha et al. have evaluated laparoscopic surgery in endometriosis surgery with colectomy and report that it is also effective in alleviating abdominal symptoms and preserving fertility . For patients undergoing sigmoidectomy, the mean operative time was 152 min and mean blood loss was 10 mL. For patients undergoing rectal resection, the mean operative time was 282 min and mean blood loss was 17 mL. Two cases had severe pelvic adhesions, and the residual rectum could not be straightened. Therefore, side-to-side anastomosis was performed. For intestinal endometriosis surgery, flexible planning for the anastomosis method for a residual intestine should be undertaken.