Endometriosis is a condition where endometrial tissue begins to grow outside the uterine cavity. This ectopic tissue most commonly implants on pelvic organs such as the ovaries and fallopian tubes, but it can also affect the gastrointestinal tract. When this tissue invades the walls or surface of the intestines, it is specifically referred to as bowel endometriosis. This condition can cause significant digestive and pelvic health issues.
Understanding Bowel Endometriosis
Bowel involvement is the most common form of endometriosis found outside of the reproductive organs, affecting an estimated 5% to 12% of all women with endometriosis. The ectopic tissue primarily targets the lower portion of the bowel, specifically the rectosigmoid colon, which is involved in up to 90% of cases. The disease presents in two main forms: superficial and deep infiltrating endometriosis (DIE).
Superficial lesions grow only on the outermost layer of the bowel wall, called the serosa. Deep infiltrating endometriosis (DIE) involves lesions that penetrate more than 5 millimeters beneath the surface, often reaching the muscular layer of the intestinal wall. This deep infiltration causes significant localized inflammation, leading to dense scar tissue and adhesions that can distort the bowel’s normal anatomy. The ectopic tissue responds to hormonal fluctuations, resulting in microscopic bleeding, inflammatory reactions, pain, and scarring within the bowel wall.
Recognizing the Signs
The symptoms of bowel endometriosis are highly variable, depending on the lesion’s size, depth, and location. A defining feature is the cyclical nature of symptoms, which typically worsen during menstruation because the misplaced tissue is hormonally responsive.
Patients commonly experience painful bowel movements, medically termed dyschezia, often most pronounced during their period. Other specific gastrointestinal symptoms include cyclical rectal bleeding, abdominal bloating, severe abdominal pain, and alterations in bowel habits, such as alternating constipation and diarrhea.
The symptom complex of pain, bloating, and altered bowel habits often leads to a misdiagnosis of Irritable Bowel Syndrome (IBS). The gastrointestinal symptoms can be difficult to distinguish from IBS, leading to diagnostic delays. However, the strong cyclical pattern, especially severe pain during defecation linked to the menstrual cycle, is a strong indicator that the underlying cause may be endometriosis.
Confirming the Diagnosis
The path to a definitive diagnosis begins with a comprehensive medical history. A physical examination, including a pelvic exam, can sometimes reveal palpable nodules or signs of deep infiltrating disease in the rectovaginal septum. Following this initial assessment, imaging techniques are employed to visualize the lesions and plan further management.
Transvaginal ultrasound (TVUS) is often the first-line investigation for suspected intestinal endometriosis. It is non-invasive, widely available, and highly accurate for detecting deep infiltrating lesions, especially in the rectosigmoid area. Magnetic Resonance Imaging (MRI) is useful for visualizing the full extent of deep infiltrating endometriosis (DIE) in complex cases and for preoperative surgical mapping.
A standard colonoscopy is typically a poor diagnostic tool because the lesions usually grow on the outside of the bowel wall and only rarely penetrate the inner lining (mucosa). Colonoscopy may only detect the disease if the lesion has grown significantly enough to cause a transmural stricture or if the endometriosis has eroded through the wall. Ultimately, the gold standard for definitive diagnosis and staging remains surgical visualization and biopsy, typically performed via laparoscopy.
Medical and Surgical Management
Treatment for bowel endometriosis is highly individualized, depending on the severity of symptoms, the extent of the disease, and the patient’s desire for future fertility. Medical management focuses on hormonal suppression to alleviate symptoms by inhibiting the growth and activity of the ectopic tissue. Hormonal therapies include combined oral contraceptives, progestins (such as norethindrone), and gonadotropin-releasing hormone (GnRH) agonists.
These medications work by creating a low-estrogen environment, which helps to reduce the inflammation and pain associated with the hormonally-responsive lesions. Hormonal suppression can significantly improve pain and gastrointestinal symptoms, especially in cases where the bowel stenosis is not severe. Medical therapy is frequently used for patients with mild to moderate symptoms or post-operatively to reduce the risk of disease recurrence.
For severe cases, particularly those involving significant deep infiltration, bowel obstruction, or debilitating pain refractory to hormonal treatment, surgical management is necessary. Minimally invasive surgery, such as laparoscopy, is the preferred approach and involves three primary techniques: shaving, disc excision, and segmental resection.
Shaving excision involves carefully removing the lesion layer-by-layer from the bowel wall and is the most conservative approach, often used for superficial lesions. Disc excision removes a full-thickness, circular portion of the bowel wall containing the lesion, and the remaining tissue is closed.
Segmental resection is the most aggressive technique, involving the complete removal of an entire segment of the diseased bowel, followed by rejoining the healthy ends (reanastomosis). This procedure is reserved for large, obstructive lesions or when multiple lesions are present, especially if they involve more than half of the bowel’s circumference. The decision between these techniques requires a multidisciplinary approach, often involving both gynecologic and colorectal surgeons.