A colonoscopy is a procedure used to examine the inner lining of the large intestine, or colon, for abnormalities like polyps or cancer. A rectocele is a structural defect where the wall of the rectum bulges into the vagina. Because a colonoscopy focuses on the inside surface of the bowel, it is not the definitive tool for detecting a rectocele, which is a concern involving the structure outside the rectal wall. Understanding the difference in the purpose and scope of each condition is key to seeking the right diagnosis.
Understanding a Rectocele
A rectocele is a form of pelvic organ prolapse where the front wall of the rectum pushes into the back wall of the vagina. It occurs when the tissue between the rectum and the vagina, called the rectovaginal septum, becomes weakened or stretched.
The causes of this weakening relate to events that place stress on the pelvic floor. Childbirth, especially multiple vaginal deliveries or deliveries involving a large baby, forceps, or significant tearing, is a common factor. Chronic straining from constipation and the natural loss of muscle tone associated with aging also contribute to the development of a rectocele.
Rectoceles often present with symptoms related to obstructed defecation, such as difficulty fully emptying the bowels or the sensation that stool remains trapped. Some women may find they need to apply pressure to the back wall of the vagina (manual splinting) to help complete a bowel movement. Other common symptoms include a feeling of pressure or fullness in the pelvis and noticing a soft bulge of tissue in the vagina.
The Purpose of a Colonoscopy
A colonoscopy is a medical procedure that inspects the inner surface, or mucosa, of the entire large intestine and the rectum. A long, flexible tube called a colonoscope, equipped with a camera and light, is inserted through the anus to perform this examination.
The procedure screens for and prevents colorectal cancer by identifying and removing polyps. It is also used to investigate symptoms like rectal bleeding, unexplained changes in bowel habits, or chronic diarrhea. The physician uses the scope to look for mucosal abnormalities, such as inflammation from conditions like ulcerative colitis, sources of bleeding, or cancerous lesions.
The procedure is an internal, mucosal examination, focusing on the superficial layer lining the inside of the bowel. It is not designed to assess the strength or structural integrity of the surrounding pelvic floor muscles and connective tissues.
Direct Answer: Why Colonoscopy Misses Structural Issues
A colonoscopy is not a definitive test for a rectocele because the rectocele is a structural defect located outside the inner channel, or lumen, of the rectum. The issue is a weakness in the supporting wall, not a problem with the rectal lining itself.
The colonoscope is advanced through the lumen and is focused on viewing the health of the mucosal surface. It provides a direct visual assessment of the internal lining but cannot directly visualize the surrounding supportive structures, like the rectovaginal septum or the pelvic floor muscles. While a very large rectocele might cause an indentation or external compression visible from the inside of the rectal lumen, this finding is secondary and non-specific.
The procedure looks for mucosal lesions, such as polyps or inflammation. A rectocele, being a structural defect, does not typically cause these types of mucosal abnormalities. A gastroenterologist performing a colonoscopy is focused on ruling out mucosal disease and is not positioned to accurately diagnose the degree of pelvic organ prolapse.
Definitive Diagnostic Imaging
The diagnosis of a rectocele begins with a physical examination performed by a gynecologist, urogynecologist, or colorectal surgeon. This examination involves assessing the vaginal wall while the patient performs a Valsalva maneuver (a bearing-down effort). This effort makes the prolapse more visible and allows the clinician to grade its severity.
For a definitive diagnosis and to assess the functional impact of the rectocele, dynamic imaging tests are used, especially when symptoms are severe or before surgery. These tests include defecography or MR defecography.
These specialized tests use contrast material placed in the rectum to visualize the pelvic organs and their movement in real-time as the patient attempts to evacuate. Defecography confirms the presence and size of the rectocele and determines if stool is being trapped within the bulge. Dynamic magnetic resonance imaging (MR) provides a detailed assessment of the soft tissues and multiple pelvic compartments, allowing for a comprehensive evaluation of the pelvic floor structure.