As a result of a colonoscopy, the doctor is able to examine the entire rectum and colon of a patient while he or she is sedated. Performing this test is the specialty of a colonoscopist. The diagnosis of colorectal cancer depends on the surgical removal of the tumor for a clear picture of its location and spread.

Identifying specific genes, proteins, and other tumor-specific factors may be recommended by your doctor through laboratory testing. Tests of the tumor’s molecular composition may also be called molecular pathology.

People with colorectal cancer may become anemic because of bleeding into their large intestine and rectum. CBC tests, which measure the number of red blood cells in the blood, can indicate bleeding.Colorectal cancer patients who are currently receiving treatment often undergo CEA tests to track their progress.

CT scans use x-rays taken from various angles to take pictures of the inside of the body. These images are then combined by a computer into a detailed, three-dimensional image. The size of the tumor can be measured with a CT scan.  

An MRI produces detailed images of the body using magnetic fields rather than x-rays. A tumor’s size can also be measured using this technique.  

By using sound waves, an ultrasound creates a picture of the internal organs to determine if cancer has spread. In order to determine the depth of rectal cancer, an endorectal ultrasound is often used.    

A small amount of radiation can be used to create an x-ray image to show the internal structures of a person. In detecting if cancer has spread to the lungs, doctors can use an x-ray of the chest.  

In a PET scan, organs and tissues are visualized inside the body. The patient is injected with a small amount of radioactive sugar substance. Using a scanner, the inside of the body is visualized by detecting this substance.