The Bowel

The bowel is part of the digestive system and is responsible for processing food, absorbing nutrients and removing waste from the body.

It is divided into two main sections:

• Small intestine, where most nutrients, vitamins and minerals are absorbed.
• Large intestine, which includes the colon, rectum and anus. This is where water is absorbed and stool is formed before being passed from the body.

Colorectal cancer can develop in the colon or rectum and, in many cases, originates from precancerous polyps that grow slowly over several years. For this reason, early detection is one of the most effective strategies for reducing mortality from this disease.

Colorectal Cancer Screening

Screening programmes can detect precancerous lesions or cancers at an early stage, before symptoms develop. When colorectal cancer is diagnosed early, the chances of successful treatment and cure are significantly higher.

In Spain, population-based colorectal cancer screening is included in the National Health System (SNS) Common Services Portfolio and is aimed at men and women aged 50 to 69 years. Some autonomous communities are progressively expanding the eligible age ranges in line with updates to their screening programmes.

Faecal Immunochemical Test (FIT)

The currently recommended screening test is the Faecal Immunochemical Test (FIT), which detects small amounts of blood in the stool that are not visible to the naked eye.

The test involves collecting a small stool sample at home and sending it for laboratory analysis.

Negative Result

A negative result means that no blood has been detected in the sample analysed. However, no screening test is perfect, which is why it is important to repeat screening at the intervals recommended by the programme.

Positive Result

A positive result does not necessarily mean that cancer is present. Blood in the stool can be caused by a range of conditions, including:

• Polyps.
• Haemorrhoids.
• Inflammatory bowel disease.
• Diverticular disease.
• Colorectal cancer.

In these cases, a colonoscopy is recommended to identify the source of the bleeding.

Invalid or Insufficient Samples

Occasionally, the test may need to be repeated because of an error during sample collection or a technical issue in the laboratory. This does not imply the presence of cancer.

Colonoscopy

Colonoscopy is the gold-standard investigation for examining the colon and rectum.

It involves gently inserting a flexible tube with a high-definition camera (colonoscope) through the anus to allow direct visualisation of the lining of the bowel. During the procedure, biopsies can be taken and polyps can be removed.

Preparation

For the examination to be effective, the bowel must be completely clean. This usually requires:

• Following specific dietary instructions.
• Taking a bowel-cleansing laxative preparation the day before the procedure, or according to the instructions provided by the healthcare team.

Detailed preparation instructions will be provided in advance.

During the Procedure

Most colonoscopies are performed under conscious sedation or deep sedation to improve patient comfort. The procedure usually takes between 20 and 45 minutes.

Benefits

Colonoscopy not only allows colorectal cancer to be diagnosed, but can also help prevent it by detecting and removing precancerous polyps before they develop into a malignant tumour.

CT Colonography (Virtual Colonoscopy)

CT colonography, also known as virtual colonoscopy, uses a CT scanner to obtain detailed images of the colon and rectum.

It may be considered in specific situations, such as:

• When a conventional colonoscopy cannot be completed.
• When there is a contraindication to conventional colonoscopy.
• In selected clinical circumstances following specialist assessment.

Like conventional colonoscopy, CT colonography requires appropriate bowel preparation.

It is important to note that if a suspicious lesion is identified, a conventional colonoscopy will usually still be required to confirm the diagnosis and/or obtain a biopsy.

Techniques Rarely Used Today

Barium Enema

A barium enema was widely used in the past to examine the colon using X-rays and contrast medium.

However, current clinical practice and international guidelines have almost entirely replaced this technique with colonoscopy and CT colonography, as these methods offer superior diagnostic accuracy. Today, its use is exceptional.

Frequently Asked Questions About Colorectal Cancer Screening

At What Age Should I Take Part in the Screening Programme?

In Spain, the population screening programme is primarily aimed at men and women aged 50 to 69 years as part of the National Health System's Common Services Portfolio. Some autonomous communities may gradually expand eligibility according to their local programmes.

What If I Have a Family History of Colorectal Cancer?

People with a significant family history of colorectal cancer or hereditary cancer syndromes may require specific surveillance strategies that differ from those used in population screening programmes. In these situations, it is advisable to consult your GP, a gastroenterologist or a specialist in genetic counselling.

Is Participation in Screening Mandatory?

No. Participation is voluntary. However, accepting the invitation is strongly recommended because screening has been shown to reduce mortality from colorectal cancer and allows abnormalities to be detected before symptoms develop.

Do I Need to Change My Diet Before the Stool Blood Test?

No. The faecal immunochemical test (FIT) currently used does not require any special dietary restrictions or changes to your regular medication, unless specifically advised by your healthcare team.

Should I Have a Colonoscopy If I Have No Symptoms?

Colonoscopy is not recommended as a routine screening test for the entire average-risk population within Spanish population screening programmes. It is usually performed when the FIT result is positive or when risk factors or symptoms justify further investigation.