What is a Colonoscopy?
A colonoscopy is a diagnostic procedure that lets your doctor closely examine the inner lining of your large intestine (colon) using a thin, flexible tube equipped with a small video camera.
{"A colonoscopy screens for colon cancer, polyps, and other digestive conditions","The procedure is typically performed under sedation for comfort","Preparation involves a special diet and bowel cleansing the day before","It is recommended for adults aged 45-75, or earlier if you have risk factors","The test usually takes 30-60 minutes and you can resume normal activities the next day"}
Key facts at a glance
- LOINC
- 111829-8
- Short code
- COL
- Synonyms
- Background information Colonoscopy
- Category
- cardiac
- Sample
- serum
- Container
- Not applicable - this is a narrative procedure report
- Units
- N/A
- Ref low
- 22
- Ref high
- 198
- Critical range
- — – 10000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- colonoscopy
- CPT
- 45378
- SNOMED
- 73761001
- Specimen volume
- Not applicable
- Stability
- Not applicable
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–72 hours
- Order
- routine
What is a Colonoscopy?
A colonoscopy is a medical procedure where a doctor uses a thin, flexible tube called a colonoscope to look inside your colon. The tube has a small camera on the end that sends images to a monitor, allowing the doctor to see the entire colon and rectum. During the procedure, the doctor can also remove polyps (abnormal growths) and take tissue samples if needed.
Why is This Test Performed?
Colonoscopies are primarily used to: (1) Screen for colon cancer, which is one of the most common cancers worldwide; (2) Detect and remove polyps before they become cancerous; (3) Investigate symptoms like rectal bleeding, chronic diarrhea, abdominal pain, or unexplained weight loss; (4) Monitor patients with a family history of colon cancer or inflammatory bowel disease.
How to Prepare for the Procedure
Proper preparation is essential for an accurate examination. You will need to: (1) Follow a special diet 1-3 days before - typically clear liquids only the day before; (2) Take bowel-cleansing medications (laxatives) as prescribed to empty your colon; (3) Inform your doctor about medications you take, especially blood thinners; (4) Arrange for someone to drive you home after the procedure since you will receive sedation.
What Happens During the Test?
You will lie on your side while the doctor inserts the colonoscope through your rectum and slowly advances it through your colon. Air is pumped in to expand the colon for better viewing. The procedure usually takes 30-60 minutes. You will be given sedatives to minimize discomfort. If polyps are found, they are typically removed during the procedure and sent to a laboratory for analysis.
After the Procedure
You will rest in a recovery area until the sedation wears off, usually 30-60 minutes. You may feel bloated or have gas cramps due to the air used during the procedure - this is normal and should resolve within a few hours. You can resume your normal diet the same day, though it's best to avoid heavy meals initially. If any tissue samples were taken or polyps removed, your doctor will discuss the results with you in a follow-up appointment.
Reference range
Adult males: 22-198 U/L; Females: 22-198 U/LN/A
Patients must complete bowel preparation as instructed. Inform patient about procedure risks, benefits, and obtain informed consent. Discontinue anticoagulants as directed by physician. Maintain clear liquid diet day before procedure. No solid food after midnight prior to colonoscopy.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Colonoscopy is considered the gold standard for colorectal cancer screening. It can detect cancer at early, treatable stages and allows for immediate removal of precancerous polyps. Regular colonoscopies can reduce the risk of dying from colon cancer by up to 70%. The procedure also helps diagnose inflammatory bowel diseases, diverticulosis, and other colon conditions. Early detection through colonoscopy significantly improves treatment outcomes and survival rates.
Frequently asked questions
Is a colonoscopy painful?
How often do I need a colonoscopy?
What are the risks of colonoscopy?
Can I resume normal activities after the procedure?
What if polyps are found during my colonoscopy?
Sources
- 1
- 2
- 3
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy