In a diagnostic colonoscopy, a doctor uses a tiny camera attached to the tip of a long, thin, flexible tube to examine the entire large intestine or colon. They are looking for abnormalities such as colorectal cancer or colorectal polyps in the large intestine and the rectum. 

How to Know When to Go

If you are experiencing any of the following symptoms, see your doctor. 

  • Rectal bleeding 
  • Abdominal pain
  • Chronic constipation or chronic diarrhea 

After examining you and ruling out any other possibilities, the doctor may choose to order a diagnostic colonoscopy to further examine what else may be causing the symptoms. 

Prepare for the Procedure

If your doctor orders a diagnostic colonoscopy, he will ask you to clean out your colon. To do this, you may be asked to follow a special diet and take a laxative the day before the exam and possibly take a laxative the day of the examination as well. The doctor will need to know ahead of time which medicines you are taking so he can take precautions accordingly. You may be asked to stop taking some medicines temporarily or to possibly adjust the dosages. 

During the Procedure 

The procedure usually lasts about 30 to 60 minutes. Prior to the procedure, you should expect a sedative either in pill form or through an IV to minimize any pain. The doctor will insert the colonoscope into your rectum while you are lying on your side on the table with your knees pulled up to your chest. 

While the colonoscope is inside your colon, the doctor will pump air through the tube into your colon. This widens the colon to give the doctor a better view. During this procedure, you may feel cramping or the urge to make a bowel movement.

The camera on the colonoscope lets the doctor see the inside of your colon as it is moving through. If the doctor sees anything out of the ordinary, he could insert instruments through the tube as well to remove polyps or to take tissue samples for a biopsy. 

After the Procedure 

When the procedure is complete, you will need at least an hour to recover from the sedative and will need a ride home. The sedative may take a full 24 hours to wear off. Do not expect to be able to drive home or return to work until at least the next morning.

The air that was pumped into your colon during the procedure may cause bloating or may cause you to pass gas later. If this happens, walking will help to ease any discomfort.

If you notice a small amount of blood in your first stool following the exam, just let your doctor know, especially if you continue to pass blood or have blood clots.

The Results Are In!

If you get a negative result, it means they didn’t find anything and your doctor will have you come back for another exam in one to ten years, depending on your risk factors. 

If you get a positive result, it means the doctor found some abnormalities such as polyps or abnormal tissue. If the doctor removed any polyps they will be sent to the lab for a biopsy. Some polyps can be cancerous or precancerous, but most are not. 

Your doctor may recommend another exam or surgery if your doctor finds large polyps or abnormal tissue that could not be removed in the first exam.


A diagnostic colonoscopy is performed on someone who has a complaint or condition. It is the same test but it is done for a specific reason such as bleeding, pain, a change in bowel habits, diarrhea, or constipation. These are present symptoms that make us want to look at the colon as a potential problem. If surgery is required, the professionals at Nevada Surgery & Cancer Center in Las Vegas can help.