Doctor talking to his male patient

Colorectal Cancer Diagnosis: An Overview


  • Early colorectal cancer diagnoses have significantly improved survival rates.
  • Doctors use many diagnostic tools, including physical exams, blood tests, and FIT or FOBT screening.
  • The only way to establish a diagnosis with 100% certainty is through a biopsy.
  • At-home colorectal cancer tests are a convenient way to improve detection, diagnosis, and survival rates. 

Colorectal cancer cases and survival rates are on the decline, and diagnostic and screening improvements play a significant role in the improvements. In this blog post, we’ll look at those rates, how doctors diagnose colorectal cancer, the important role that early detection has played in these promising trends, and what it all means for you. 

The Numbers Are Encouraging

Based on data from the National Cancer Institute, we can conclude that new colorectal cancer cases and deaths have plummeted over the last few decades. At the same, survival rates have improved. 

  • From 1976 to 2019, colorectal cancer deaths have gone down from 61.3 per 100,000 people to 12.8.
  • New cases peaked in 1985 at 66.6 per 100,000 people. In 2018, doctors diagnosed 35 new cases per 100,000 people.
  • From a 49.6 percent survival rate in 1975, we arrived at 67.9 percent in 2014. 

Your chance of being diagnosed with colorectal cancer is currently 4.1 percent. Better diagnostic tests, regular screening, and early detection are partially responsible for these dramatic improvements.

Colorectal Cancer Diagnosis and Staging

Doctors use a wide range of colorectal cancer diagnostic tools and methods. Some are more invasive than others, but all have a place in the arsenal used to fight the disease. 

To determine which diagnostic tool or method to use, doctors consider the following factors:                      

  • The patient’s symptoms 
  • The type of cancer suspected
  • Conclusions drawn from earlier tests
  • The patient’s general health and age

Physical Exam

A physical exam is the first step to establishing if something is wrong with your colon. During your exam, your doctor may insert a lubricated, gloved finger into your rectum to feel around for lumps that shouldn’t be there. Your doctor will also feel your abdomen and may examine your prostate.

Discussing your medical history and family history of colorectal cancer is also essential for establishing your risk profile. During the initial stage of the examination, you can talk to your doctor about any symptoms you may have.

Your doctor may also consider environmental and lifestyle factors to help determine your risk. 

Colorectal Cancer Screening Tests

The next step in the diagnostic process is screening. Non-invasive colorectal screening tests look for blood in your stool. Some blood may be visible, but if cancerous lesions cause bleeding deep inside your colon, you won’t be able to see the blood with the naked eye. To detect this internal bleeding, your doctor will recommend stool testing.

Fecal Occult Blood Tests (FOBT)                         

FOBT tests require a stool specimen you can collect in the privacy of your home. Collect samples from three different bowel movements to cast a wider net for possible problems. FOBT tests use a chemical that changes color when it comes in contact with blood from the stool sample. 

Fecal Immunochemical Tests (FIT) 

FIT also requires stool samples from three bowel movements. Instead of a color-changing chemical agent, FIT-testing uses antibodies linked to hemoglobin to detect blood. 


Of the two screening methods, FIT has better detection rates and is more popular. Many home colorectal cancer tests use the FIT method, as it’s more reliable. 

You can order a colorectal screening test kit online, collect your stool samples, and mail them to a lab. In a few days, you’ll get your results online. If your test is positive, your doctor may recommend further tests to confirm a colorectal cancer diagnosis. 

Colorectal screening test kits are non-invasive, easy to use, and usually more affordable than an office visit.         

Blood Tests

In addition to stool screening, doctors may order blood tests to help with diagnosis or to monitor the disease. Blood tests alone can’t diagnose colon cancer. In many colon cancer patients, blood work turns out normal. In others, abnormal results appear for other reasons. 

Blood work can, however, provide additional information that can help doctors make an accurate diagnosis. Doctors may use blood tests to screen for any of the following: 

  • Tumor markers. Cancer cells create tumor markers that may show up in blood tests. Colorectal cancer may produce carcinoembryonic antigen.
  • Liver abnormalities. Liver enzymes offer clues about the functioning of your liver. If colon cancer spreads to the liver, it may disturb these enzymes.
  • Anemia. Anemia, a shortage of red blood cells, can be caused by excessive bleeding. Some colon cancers may cause significant blood loss. 

Colonoscopy and Biopsy

If your doctor suspects cancer after diagnostic testing, they will likely order a colonoscopy and/or biopsy. 


Colonoscopy is one of the most effective colorectal cancer screening methods. It is also doctors’ top choice for colon cancer diagnosis.

During a colonoscopy, the doctor will insert a thin, flexible tube through your rectum and colon. The colonoscope has a light at the end, a camera, and an opening through which the doctors can use various tools to collect samples and remove polyps. 

In addition to diagnosing colon cancer, doctors might be able to treat early-stage colon cancer through colonoscopy. 

Biopsy and Biomarker Testing 

The only way to diagnose colorectal cancer beyond doubt is to take a tissue sample and analyze it under a microscope. Doctors can take biopsies during a colonoscopy. In addition to diagnosis, biopsy and colonoscopy can help doctors determine the stage of colon cancer. 

By analyzing a biopsy at the molecular level, doctors can determine the best treatment options for a tumor. They can see, for instance, if immunotherapy is a viable treatment option. They can also determine if a patient has Lynch syndrome


Proctoscopy is similar to colonoscopy, but instead of visualizing the lining of your colon, the doctor will examine the lining of your rectum. Doctors use a smaller, rigid probe for proctoscopy. 


Doctors may use imaging to determine how far cancer has spread in the body, how well treatment is working, and whether cancer has returned in a previously treated patient. 

Computed Tomography (CT)

A CT scan creates high-resolution images of the patient’s internal organs using X-rays. Doctors use CT to determine where cancer has spread in the body. They may also use CT to take needle biopsies to establish a conclusive diagnosis. 


Ultrasound equipment emits high-frequency sounds that bounce off internal organs to create images. 

There are several ways doctors can use ultrasound to look for problems.

  • Abdominal ultrasound. The technician uses a transducer on the surface of the skin.
  • Endorectal ultrasound. The transducer is inserted into the rectum.
  • Liver ultrasound. Doctors can use ultrasound on the surface of the liver during an operation. 

Magnetic Resonance Imaging (MRI)

MRI works similarly to CT, but instead of X-rays, it uses magnets and radio waves to create high-resolution images of internal organs and soft tissue. 

Positron Emission Tomography (PET) 

PET scans use radioactive sugar injected into the patient’s body. These sugar particles gather in cancerous cells, highlighting the problem areas. 


Angiography requires doctors to inject a dye into the veins of the patient to highlight them on X-ray images. Doctors use this technique to determine whether they can remove tumors or must resort to other treatment options. 

Home Colorectal Cancer Tests

The early detection and early diagnosis of colorectal cancer saves lives. FIT colorectal screening test kits can reduce mortality from colorectal cancer by 15-33 percent in people aged 50-80 when performed every one to two years.

Home colorectal cancer screening is a convenient way to reduce your risk. Home colorectal cancer test kits are 92 percent effective in detecting colorectal cancer. They’re affordable, accurate, and easy to use.  

eDrugstore Can Help

We carry FIT colorectal screening test kits you can order and have delivered quickly and discreetly. If your results turn out positive, our U.S.-licensed doctors will advise you on how to proceed, free of charge. 

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