Gastrointestinal endometriosis accounts for 5 to 10% of all cases of endometriosis, and 70 to 90% of such cases occur in the sigmoid colon and rectum . Symptoms of rectal endometriosis include melena, narrowing of stool, constipation, and abdominal pain, but these symptoms are not always present. Likewise, menstrual symptoms are not always present. Rectal endometriosis can cause perforation or acute bowel obstruction [9, 10].
In rectal endometriosis, severe fibrosis around the rectal wall occurs because of repeated bleeding and inflammation of the endometrial tissue in the wall. Magnetic resonance imaging findings may reflect this bleeding and inflammation . The most useful diagnostic method is laparoscopy. In addition to peritoneal lesions such as blueberry spots, ectopically growing endometrial tissue can be observed on the surface of the intestinal serosa, and biopsy specimens can be obtained from this tissue. Our patient developed constipation without menstrual symptoms. Diagnostic laparoscopy revealed a chocolate cyst and adhesion between the cyst and the rectum. She had no additional findings suggesting endometriosis. Therefore, we preoperatively diagnosed malignant-like lesions such as type 4 rectal cancer or a gastrointestinal stromal tumor.
The treatment of gastrointestinal endometriosis aims to relieve symptoms and improve infertility. Medication therapy is the first choice, but it is less effective for stricture lesions. There are reports of stent placement or balloon dilation for stricture lesions, but they eventually required surgery. These treatments are the aspects of the bridge to surgery . Surgical treatment is selected when melena or an obstruction is present or when symptom relief with medical therapy is difficult . Because intestinal endometriosis is a benign disease, excessively invasive therapy should be avoided. Laparoscopic surgery has historically been performed, and robot-assisted laparoscopic surgery has been recently reported in an effort to decrease surgical invasiveness. In patients with gastrointestinal endometriosis, especially rectal endometriosis, the ovary, uterus, and deep pelvis are often simultaneously affected by endometrial tissue. Deep pelvic endometriosis may be close to or involved in the ureter and pelvic plexus. Injury to these organs can cause serious complications. The advantages of laparoscopic surgery include good operability in a narrow space and a magnifying effect. The advantages of robot-assisted surgery include stability of the operative field and free movement of forceps, in addition to the advantages of laparoscopic surgery. Our patient had a chocolate cyst in the left ovary, the adhesion between the left pelvic wall and rectum was strong, and adhesive delamination was complicated [14, 15]. Especially in the case of adhesive delamination around the peritoneal reflection, the robot-assisted surgery showed a higher advantage in the stability of the operative field and the operability of the forceps compared with the standard laparoscopic surgery.
At our institution, since this surgical procedure was covered by insurance in 2018, we have actively applied this procedure for case of upper rectum and lower rectum disease after giving sufficient informed consent. Then, we performed robot-assisted laparoscopic low anterior resection with D3 lymphadenectomy. In rectal endometriosis, lesions may be found in lymph nodes. Some reports have linked this pathological significance to the malignant transformation of the lesions, but the details are unknown and malignant transformation is very rare. Therefore, lymphadenectomy is not always required unless a malignant disease is suspected . The extent of stenosis was estimated to be 2 to 3 cm in the upper rectum by barium enema (Fig. 1c, d). Intraoperative findings showed that the adhesion had strongly spread from the area of the stenosis to the anus. In the resected specimen, submucosal tumor-like lesions extended for about 10 cm, and endometriotic lesions were present in the broad area of the resected specimen (Fig. 4). These widespread lesions might have resulted in the rectal stenosis. Because of the chocolate cyst and possible residual intestinal endometriosis, we considered that hormonal therapy was necessary to prevent recurrence after surgery .