Endometriosis is a common condition where tissue similar to the lining of the uterus grows outside the uterine cavity. This misplaced tissue responds to hormonal signals during the menstrual cycle, leading to chronic inflammation and pain. Endometriosis can definitively cause rectal bleeding, although it is less common than other gastrointestinal issues. When this symptom occurs monthly, it strongly indicates that the misplaced tissue has implanted on the wall of the bowel or rectum.
How Endometriosis Affects the Rectum and Bowel
Endometriosis involving the gastrointestinal tract occurs in a small percentage of individuals, most frequently targeting the rectosigmoid colon. When the tissue penetrates more than five millimeters beneath the surface of the affected organ, it is classified as Deep Infiltrating Endometriosis (DIE). Lesions typically implant initially on the serosa, the outermost layer of the bowel wall, before growing deeper.
Rectal bleeding occurs when the endometriotic tissue infiltrates through the muscle layers and reaches the submucosa, sometimes causing ulceration of the inner lining (mucosa). Because this misplaced tissue is hormone-responsive, it swells and bleeds during the menstrual period. This cyclical shedding manifests as blood in the stool, termed catamenial rectal bleeding. The presence of these deep lesions can also cause severe pain during bowel movements (dyschezia), along with constipation or diarrhea that often worsens during menstruation.
Other Potential Causes of Rectal Bleeding
Rectal bleeding is a common symptom that physicians must investigate to rule out more frequent or serious conditions. The majority of cases stem from benign causes located low in the digestive tract. Hemorrhoids, which are swollen veins in the anus or lower rectum, are the most common source of bright red blood found on toilet paper or in the bowl.
Anal fissures, which are small tears in the lining of the anal canal often caused by passing hard stools, are another frequent cause of pain and bleeding. Other possible diagnoses include diverticulosis, where small pouches form in the wall of the colon and may bleed, or inflammatory bowel diseases (IBD) such as Crohn’s disease or ulcerative colitis. Any instance of rectal bleeding must be professionally evaluated, as it can be a sign of colorectal cancer. A medical consultation is necessary to determine the source of the bleeding, regardless of a known endometriosis diagnosis.
Identifying Bowel Endometriosis
Diagnosing endometriosis as the cause of rectal symptoms requires a specialized approach, beginning with a detailed patient history correlating symptoms with the menstrual cycle. Clinical suspicion is raised when a patient reports cyclical symptoms like painful defecation, rectal bleeding, and deep pelvic pain. Definitive diagnosis relies on advanced imaging techniques that visualize the lesions and determine the depth of infiltration.
Transvaginal ultrasound (TVUS) performed by a specialist, often with specific bowel preparation, can be highly effective in identifying deep infiltrating nodules on the rectum and sigmoid colon. Magnetic Resonance Imaging (MRI) is a valuable tool, offering detailed images that help map the size, location, and extent of the disease before surgical planning. A standard colonoscopy is essential for ruling out other internal causes like polyps or cancer, but it frequently misses superficial endometriosis because the lesions are typically located outside or deep within the bowel wall. This diagnostic complexity underscores the need for consultation with an endometriosis specialist or a colorectal surgeon.
Treatment Options for Rectal Endometriosis
Treatment for bowel endometriosis is determined by the severity of symptoms, lesion size, and depth of penetration into the bowel wall. Medical management, primarily involving hormonal suppression through medications like oral contraceptives or GnRH agonists, can help control symptoms by reducing cyclical stimulation. However, deeply infiltrating lesions often respond poorly to hormonal treatment alone, making surgery the most effective approach for long-term symptom relief and disease removal.
Shaving or Superficial Excision
Surgical intervention is tailored to the lesion’s extent and is typically performed laparoscopically by a multidisciplinary team. For smaller, less invasive lesions, a conservative technique known as shaving or superficial excision is employed. This method carefully dissects the nodule from the bowel wall without entering the bowel lumen, and is associated with lower complication rates and a shorter recovery time.
Segmental Bowel Resection
When the lesion is large, involves more than half the bowel’s circumference, or penetrates deeply through the muscle layers, a segmental bowel resection may be necessary. This radical procedure involves removing the affected segment of the colon or rectum entirely and then reconnecting the healthy ends (anastomosis). While segmental resection offers the highest chance of complete disease removal, it carries a greater risk of complications, including changes in bowel function and potential nerve damage.