Colon & Rectal Screening and Diagnosis | Medstar Health

A series of diagnostic tests are used to measure the strength of the anal sphincter muscles, the nerves serving the muscles, the integrity of the muscles, the mechanics of defecation, and the rate of transit through the colon. Screening exams are a powerful tool in the fight against colorectal cancer. Regular screenings enable physicians to detect cancer early and to identify and remove polyps, growths of tissue on the lining of the colon or rectum that can potentially become cancerous.

  • Colonoscopy: A colonoscope is a long, slender, flexible tube about the thickness of a finger that has a camera at the tip, enabling doctors to examine the entire colon. It is inserted into the body through the anus and gently guided through the rectum and colon. Patients are administered sedatives during the exam to keep them comfortable and relaxed. The test is usually done in the hospital as an outpatient procedure. The colonoscope provides the doctor with magnified images of the inner wall of the colon and rectum. If a polyp is found during the examination, instruments can be passed through the colonoscope to remove polyps or tissue samples. The lab will check the extracted tissue samples for the presence of cancer cells. Some patients may be eligible for a virtual colonoscopy, which uses advanced CT technology and computer software to produce images of the colon.
  • Defecating Proctogram: This is a test to view the mechanics of emptying the rectum. This test is performed in the radiology department. Prolapse and rectocele (bulging) are easily seen.
  • Double Contrast Barium Enema: Prior to taking an x-ray, the colon is filled with air and a white, chalky liquid called barium. The barium and air show an outline of the colon, rectum, and any polyps or abnormal tissue on the x-ray.
  • Fecal Immunochemical Test: The fecal immunochemical test is a newer test to find blood in the stool. The test is essentially performed like a fecal occult blood test, but the results tend to be more accurate.
  • Fecal Occult Blood Test: The fecal occult blood test is used to find small amounts of blood in the stool (not necessarily visible to the naked eye), which suggests the presence of polyps or cancer. This is because blood vessels at the surface of polyps or cancers are often damaged during the passage of feces, and bleed a small amount of blood into the stool.
  • Imaging Exams: If screening exams suggest the presence of cancer, advanced imaging techniques such as ultrasound, MRI, PET scans, and CT scans are used to determine if the cancer has spread to other organs and tissues.
  • Manometry: Anorectal manometry tests sensation in the anal/rectal area, the tone of the anus at rest, the voluntary squeeze, anorectal reflex, and the elasticity of the rectum. This test is performed using a small tube inserted into the anus and rectum.
  • Pudendal Nerve Test: The pudendal nerves run on each side of the pelvis, and control bladder function, sexual function and bowel sphincter muscles. This test checks the electrical conduction of the pudendal nerves. It is performed using special electrodes on the gloved, index finger pressed against the nerve site. This test is done in the office.
  • Sigmoidoscopy: A sigmoidoscope is a slender, flexible tube about the thickness of a finger that has a camera at the tip. It is inserted into the lower part of the colon through the rectum. The sigmoidoscope provides doctors with a view of the inner wall of the rectum and lower colon, allowing them to search for polyps or cancerous tissue. The tube is about two feet long so doctors can examine half of the colon. The test is performed in the physician’s office and can be uncomfortable, but is generally not painful.
  • Transit time: 20 markers are taken in a capsule on day 1. The markers can be seen on standard abdominal X-rays taken on days 4 and 7 so that the markers can be timed by their travel through the bowel.
  • Ultrasound: Using an ultrasound probe inserted into the anus, sound waves mark an array of points that are converted to an image seen on a video monitor. Viewing the pictures allows the doctors to see the integrity of the sphincter muscles. The ultrasound is also used in the rectum to measure the depth of growth of the tumors.

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