Colonoscopy
Table of contents
A colonoscopy allows the mucosa – that is, the inner surface of the rectum and colon – to be viewed directly using a flexible tube fitted with a camera. It can be used to investigate symptoms, assess a positive screening test result, monitor certain pre-existing conditions or lesions, and carry out treatments such as the removal of some polyps.
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What is a colonoscopy and what does it allow us to examine?
A colonoscopy is an endoscopic examination that allows the inside of the rectum and the colon to be viewed directly. It is used to examine the intestinal lining, identify any abnormalities and, where appropriate, take biopsies or treat certain lesions.
The procedure is carried out using a flexible tube called a colonoscope, which has a camera at one end and is carefully inserted through the anus. The usual aim is to examine the entire colon up to the caecum, where the large intestine begins. In some cases, the final section of the small intestine may also be examined.
The colonoscope has a channel through which instruments can be inserted to take tissue samples, remove certain polyps, control some bleeding or treat certain narrowings.
A colonoscopy allows for a direct assessment of the mucosa, but it does not detect all lesions in all circumstances. The quality of the examination depends, amongst other factors, on good bowel preparation, the ability to examine the intended section, and careful inspection.
When a colonoscopy may be recommended
A colonoscopy may be recommended when it is necessary to examine the colon directly to investigate symptoms, assess a previous finding, monitor high-risk situations or treat certain lesions.
It may form part of the investigation into gastrointestinal bleeding, iron-deficiency anaemia in certain circumstances, persistent diarrhoea, sustained changes in bowel habits, a possible inflammatory bowel disease, or abnormalities detected in other tests.
The decision to perform a colonoscopy is not based on a single symptom. It is assessed taking into account the patient’s age, medical history, clinical examination and previous test results.
Colonoscopy following a positive screening test
In Spain, the initial test in the population-based colorectal cancer screening programme is the faecal occult blood test.
A positive result does not in itself mean that cancer is present. A colonoscopy allows the colon to be examined, the possible cause to be identified and, where appropriate, biopsies to be taken or certain lesions to be removed.
Follow-up colonoscopy
It may be recommended following the removal of certain adenomas or serrated lesions, after treatment for colorectal cancer, or in some people with long-standing inflammatory bowel disease.
The frequency of follow-up depends on previous findings, the pathological result, whether the resection was complete, and the quality of the initial colonoscopy.
Therapeutic colonoscopy
During the same procedure, certain polyps may be removed, bleeding may be treated, or other endoscopic procedures may be carried out.
Large, complex or hard-to-reach lesions may require a planned therapeutic colonoscopy, advanced techniques or assessment by other teams.
When a polyp is removed, analysing the tissue reveals what type it is and helps to determine whether any follow-up checks are required. Not all polyps have the same significance, nor do they all require the same level of monitoring.
Would you like more information about a colonoscopy?
The team can provide further information on bowel preparation, sedation, the procedure and the situations in which it may be recommended.
Polyps, biopsies and treatment during a colonoscopy
Not all polyps are equally significant. Some adenomas and serrated lesions may progress over time, whilst others present a different risk.
The appearance observed during a colonoscopy allows for an initial assessment, but the definitive nature of many lesions is only known after they have been analysed by histopathology, that is, through microscopic examination of the tissue.
The specialist may remove a lesion, take a biopsy or document it in order to plan a subsequent procedure. The decision depends on its size, shape, location and whether it is safe to intervene at that time.
How to prepare for a colonoscopy
Bowel preparation is an essential part of the test. Its aim is to remove stools and waste that might prevent a clear view of the lining of the bowel.
Preparation usually involves a combination of temporary dietary changes, a laxative solution and specific instructions regarding fluids and fasting.
Diet and fluids
The unit will specify which foods may be eaten before the examination. A low-fibre diet is often followed during the recommended preparation period. Certain clear liquids may be permitted during part of the preparation. The team must specify which ones are suitable and up to what point they may be consumed.
Bowel preparation and fasting do not serve exactly the same purpose: the former cleanses the colon; the latter forms part of the safety measures when sedation is planned.
Laxative solution
The preparation causes frequent bowel movements that gradually become liquid. During this time, it is advisable to stay close to a toilet. You may experience a feeling of fullness, nausea, cramps, tiredness or anal irritation.
If it proves impossible to complete the preparation, or if persistent vomiting or significant discomfort occurs, you must contact the department. You must not alter the dosage or schedule on your own initiative.
Staged preparation
In many protocols, the preparation is divided into several doses, with one dose administered relatively close to the time of the colonoscopy. This strategy helps to achieve a more thorough cleansing.
The exact times must be those provided by the unit and take precedence over any general recommendations.
Medicines and medical history that must be disclosed
Before a colonoscopy, it is important to inform your doctor about:
Anticoagulants and antiplatelet agents.
Insulin and other treatments for diabetes.
Kidney, heart or respiratory disease.
Pregnancy or the possibility of pregnancy.
Allergies.
Severe constipation or inadequate bowel preparation.
Abdominal surgery or ostomies.
Other treatments that may affect bleeding, preparation or sedation.
Anticoagulants, antiplatelet agents, antidiabetic drugs or other medicines must not be discontinued without medical advice. A purely diagnostic colonoscopy does not carry the same risk profile as a complex resection; therefore, any adjustment to medication must be tailored to the individual.
Sedation during a colonoscopy and the need for a companion
A colonoscopy can be carried out with varying levels of sedation and, in some cases, without any sedation at all. The unit will explain the planned approach. Sedation helps to reduce anxiety and discomfort, although it does not guarantee that everyone will be completely asleep or that all sensations will disappear.
During sedation, vital signs such as breathing, pulse, blood pressure and oxygen levels are monitored.
When sedation is administered, it is usually necessary to be accompanied and to adhere to the restrictions regarding driving, operating machinery, consuming alcohol or carrying out activities requiring full attention for the specified period.
How a colonoscopy is performed
Before starting, the team checks the clinical indication, the quality of the bowel preparation, the patient’s medication, any allergies and relevant medical history. The patient is usually positioned on their left side to begin with. The colonoscope is inserted through the anus and advanced through the rectum and the colon.
Carbon dioxide, air or water may be used to expand the walls and visualise the mucosa. During the procedure, it may be necessary to change position or apply gentle pressure to the abdomen. The specialist suctions out fluids and debris, carefully examines the mucosa and, where indicated, takes biopsies or removes lesions.
Sometimes it is not possible to examine the entire colon due to inadequate preparation, complex anatomy, a narrowing, intolerance or safety concerns. The report must state how far the examination has been carried out and how the study should be completed if necessary.
What it feels like during a colonoscopy and what the recovery is like
During the examination, you may experience abdominal pressure, the urge to pass stools, flatulence, cramps or pain of varying intensity. The level of discomfort depends on the anatomy of the colon, the technique used, the presence of inflammation and the type of sedation administered.
The taking of biopsies from the mucosa usually goes unnoticed, although other sensations related to the movement of the colonoscope and distension may be felt. Afterwards, you may experience flatulence, a feeling of bloating, mild cramps, tiredness or drowsiness. Bowel preparation may also cause irritation of the anal area.
If biopsies have been taken or polyps removed, a small amount of blood may be present. The team will explain what is to be expected and which symptoms require further assessment.
How to interpret the results of a colonoscopy
The result should not simply be interpreted as positive or negative.
Colonoscopy with no significant findings
No lesions may be identified that explain the symptoms or the result of a previous test. This reduces the likelihood of certain visible diseases of the colon, but does not rule out microscopic abnormalities if biopsies have not been taken, diseases in other parts of the digestive tract, or lesions that could not be visualised.
Inflammation or other changes in the mucosa
The appearance may suggest inflammatory, vascular or infectious diseases, or other causes. Biopsies can help to complete the interpretation, even when the visual changes are subtle.
Polyps or excised lesions
The endoscopy report describes characteristics such as number, size and location. When tissue is sent to the laboratory, the pathological result determines its nature and helps to decide whether further monitoring is required.
Suspicious lesion
The specialist may take a biopsy, remove the lesion where appropriate, or document it to plan further tests or treatments. The endoscopic appearance provides guidance but does not always establish the definitive diagnosis on its own.
Inadequate preparation or incomplete examination
If the bowel preparation is insufficient to allow the mucosa to be examined properly, or if the intended section is not reached, the test’s ability to rule out lesions is reduced. It may be necessary to repeat the colonoscopy or to complete the assessment using another technique.
When will the full results of a colonoscopy be available?
The specialist may explain the main findings at the end of the examination. Where biopsies have been taken or polyps removed, the full results depend on the microscopic analysis of the tissue and will be available at a later date.
A sample may be insufficient or may not represent the entire lesion. If the result does not correspond to the endoscopic findings or the clinical suspicion, it may be necessary to reassess the situation or carry out further investigations.
Limitations of colonoscopy
The usefulness of the results depends on the quality and extent of the examination. Poor preparation, an incomplete examination or certain small, flat or hidden lesions may make detection difficult.
A colonoscopy primarily examines the inner surface of the rectum and the colon. It does not adequately examine most of the small intestine or the organs located outside the intestinal wall. Therefore, an examination with no significant findings does not rule out all possible causes of pain, diarrhoea, anaemia or bleeding.
Risks and possible complications of a colonoscopy
The risk depends on your state of health, the sedation used and the procedures carried out. A diagnostic colonoscopy does not carry the same risk profile as the removal of a large lesion. The most common side effects are flatulence, bloating, mild cramps, anal irritation, nausea or drowsiness.
Bleeding is more likely following a polypectomy or resection and may occur during the procedure or in the days afterwards. Perforation is a hole in the wall of the colon and may require endoscopic treatment, antibiotics, hospital admission or surgery.
Sedation may cause respiratory or circulatory complications and reactions to medication. Bowel preparation may also lead to dehydration or electrolyte imbalances, particularly in certain individuals with kidney disease, heart disease or frailty.
When to seek medical advice following a colonoscopy
The unit should provide contact details. An assessment should be requested in the event of:
Severe, worsening or persistent abdominal pain.
A very distended or hard abdomen.
Fever.
Heavy bleeding or the presence of clots.
Severe dizziness, fainting or marked weakness.
Persistent vomiting.
Difficulty breathing.
General deterioration.
A small amount of blood may appear after certain biopsies or polypectomies. If the bleeding increases, recurs or is accompanied by other symptoms, you should seek medical advice.
Colonoscopy in special circumstances
People with diabetes may need specific guidance on diet, blood glucose levels and treatment during preparation. For people with kidney or heart disease, it may be necessary to adjust the bowel preparation, fluid intake or medication.
During pregnancy, the indication, timing of the test and sedation are tailored to the individual.
Severe constipation, inadequate prior preparation, certain abdominal surgeries, stomas or inflammatory bowel disease may also require specific preparation or a specific approach.
CT colonography, capsule endoscopy and other alternatives to colonoscopy
When a colonoscopy cannot be performed or is incomplete, other techniques may be considered depending on the clinical presentation. Computed tomography (CT) colonography provides images of the colon but does not allow biopsies to be taken or polyps to be removed.
The capsule endoscopy can be used in certain selected situations and does not allow direct treatment of a lesion either. If these tests detect a significant finding, a colonoscopy may still be necessary at a later stage.
Colonoscopy specialists at Memorial Publio Cordón
At Memorial Publio Cordón Hospital, colonoscopies are carried out in the Digestive Endoscopy Unit, which forms part of the Digestive System Department.
Dr Javier Aranda Hernández is head of the Digestive Endoscopy Unit.
Other specialists involved in endoscopic procedures include Dr Ana Isabel Romero Reina, Dr Marta Cruz Aparicio and Dr Malena García Arredondo, who heads the Digestive System Department.
When biopsies are taken or lesions are removed, the Pathology Department carries out a full examination of the tissue. Complex cases may require coordination with surgery, oncology, radiology or other specialist departments.
Medical information for general guidance
This information sheet aims to help you understand why a colonoscopy might be recommended, how to prepare for and undergo the procedure, what you might experience during and after the examination, and how the endoscopic findings and biopsy results are interpreted.
Memorial Publio Cordón Hospital promotes accurate, understandable and useful medical information, linked to specialist care, research, scientific dissemination and medical progress.
The indication for a colonoscopy, bowel preparation, sedation, management of medication and interpretation of the results must be tailored to each individual’s clinical situation. The instructions provided by the Digestive Endoscopy Unit take precedence over any general recommendations.