Colorectal cancer

Diagnosis

Oncologists may diagnose colorectal cancer through the following techniques:

• Medical history and physical examination: The patients are examined to detect possible symptoms of colorectal cancer. Patients are also asked about the risk factors, family history, underlying medical conditions, and initiation and period of symptoms. During the physical examination, the abdomen of the patient is pressed to look for any abdominal enlargement.
• Stool test: Patients are advised to undergo a comprehensive stool examination for blood content. If the blood is not seen in the stool with the naked eye, the pathologists may detect the hidden blood through fecal immunochemical tests or fecal occult blood tests.
• Blood test: Blood tests help to determine cancer signs. Patients with colorectal cancer generally have anemia. The blood tests include complete blood cell count (to test anemia) and liver function tests (in case of cancer has spread to the liver). The patients may also have tumor marker tests to detect the substances released by the colorectal cancer cells. Carcinoembryonic antigen (CEA) is the most common colorectal tumor marker.
• Proctoscopy: Patients are recommended for proctoscopy if rectal cancer is suspected. Proctoscopy is the technique of viewing the rectum through a proctoscope, which is a rigid, thin tube with a camera at the end. The lining of the rectum is examined for any abnormal tissue through a proctoscope, and the exact size and location can be determined.
• Colonoscopy: The patient is recommended for a diagnostic colonoscopy if the other diagnostic tests suspect colorectal cancer. During this test, a colonoscope, a flexible, long, thin tube with a camera fitted at the end, is inserted into the anus and guides it to the rectum and colon.
• Ultrasound: Transrectal ultrasound detects the presence and extent of rectal cancer and if cancer has reached the nearby lymph nodes. Abdominal ultrasound may also be performed to detect the spread of cancer to nearby organs, such as the pancreas, liver, gallbladder, or other abdominal organs. However, abdominal ultrasound cannot detect abnormal tissues in the rectum or colon. The oncology surgeon may also perform an ultrasound of the liver during the surgery (intraoperative ultrasound) to detect the spread of cancer to the liver.
• CT scan: The patients are also advised to undergo computed tomography (CT) scan to detect the spread of cancer to the nearby lymph nodes or to the organs, such as the lungs or liver. CT scans also guide the needle during the biopsy.
• Magnetic resonance imaging (MRI): MRI detects the spread of cancer to nearby tissues and organs. It assists in planning the surgery or choosing the treatment. Endorectal MRIs are also performed to improve the accuracy of MRI results.
• Flexible sigmoidoscopy: Sigmoidoscopy is done with the help of a sigmoidoscope, a thin, long tube with a camera at the end, and is used to evaluate the sigmoid colon and rectum. The sigmoid colon is the last segment of the colon.
• Biopsy: If there is any abnormal tissue detected during any diagnostic procedure, the tissue samples are obtained for further analysis. The sampling of tissue is done during a colonoscopy. Biopsy not only helps in detecting cancer but also assists in determining the specific genes and proteins associated with the cancer cells. It helps determine if a particular therapy, for example, targeted therapy, is effective in the patient.