Colorectal cancer is a type of cancer that forms in the tissues of the colon (the longest part of the large intestine) or the rectum (the portion of the intestine closest to the anus).

Like all cancers, colorectal cancer results from the uncontrolled growth of cells, in this case the epithelial cells of the mucosa lining the inside of the intestine.
Cancers of the intestine mainly originate in the colon and rectum, while cancers of the small intestine and anal canal are much rarer (2–3% of all digestive tract cancers).
Colon cancers are nearly three times more common than rectal cancers and may present with different symptoms.

Dr. Alex Leo provides an overview of colorectal cancer and the latest research advances in the field.

According to GLOBOCAN 2020 estimates from the International Agency for Research on Cancer (IARC), colorectal cancer accounts for 10% of all diagnosed cancers worldwide, ranking third in incidence after breast and lung cancers.

This disease is relatively rare before the age of 40 and occurs more frequently in individuals aged 60 to 75, with little difference between men and women.

Risk Factors

Known risk factors for colorectal cancer are related to diet, genetics, and other non-hereditary causes.

Most colorectal cancers develop from the malignant transformation of polyps, small growths caused by the proliferation of mucosal cells in the intestine.
However, not all polyps have the potential to become cancerous.

In general, polyps do not cause symptoms, though in some cases they may lead to minor bleeding, detectable through a fecal occult blood test.
In other cases, larger bleeding visible to the naked eye or even true rectal hemorrhages may occur.

Early symptoms—such as fatigue and loss of appetite—are often vague, sporadic, and may be overlooked by patients, especially younger ones.
More serious symptoms, including anemia and unexplained weight loss, can also be ignored.
Persistent constipation, alternating with diarrhea, or irregular bowel habits, may be early warning signs that should not be underestimated.

Diagnosis

Patients presenting these symptoms should consult a specialist gastrointestinal surgeon.

Diagnosis typically includes:

  • a clinical history,
  • a physical examination, and
  • diagnostic tests.

A minimally invasive test, such as a sigmoidoscopy, may be sufficient in some cases.

What is a Sigmoidoscopy?

A sigmoidoscopy is a diagnostic procedure that allows doctors to examine the lower third of the colon.
It is useful for identifying the cause of abdominal pain, constipation, abnormal growths, or bleeding.
It can also be used to collect biopsies or to perform procedures like the removal of polyps or hemorrhoids.

A lighted tube, called a sigmoidoscope, is inserted through the anus, and air is insufflated into the colon for better visualization.

Sigmoidoscopy is typically performed on an outpatient basis and does not require anesthesia.

If necessary, the specialist may recommend a colonoscopy—a more invasive test performed by gastroenterologists in specialized centers. Colonoscopy is usually done under sedation, and rarely under general anesthesia.

Before the Procedure

  • For an outpatient sigmoidoscopy, no preparation is needed.
  • If a more invasive procedure is recommended, bowel preparation will be required.

How Long Does It Take?

An outpatient sigmoidoscopy usually lasts no more than 5 minutes.
Including the complete medical consultation, the entire appointment typically takes about 10 minutes.

Is It Painful?

Sigmoidoscopy is generally not painful. Some discomfort may be felt.
However, if the patient has acute conditions, such as anal fissures, the procedure may be painful—in these cases, it is not performed.