For a colonoscopy, you lie on your left side with your knees drawn up toward your chest. This is called the left lateral position, and it’s the standard starting position used in colonoscopy procedures worldwide. Your hips and knees are bent, and your body is curled slightly forward, similar to a fetal position. The whole procedure typically takes between 20 minutes and an hour.
Why the Left Side Specifically
The left-side position isn’t arbitrary. Your colon makes a series of turns through your abdomen, and the scope enters from the rectum on the lower left side of your body. Lying on your left keeps the initial portion of the colon in a favorable position for the scope to advance, and it allows air and fluid inside the colon to shift in ways that give the doctor a clearer view of the lining.
Gravity also plays a role. When you’re on your left side, the natural weight of your intestinal contents settles in a way that opens up the path for the scope. This makes insertion smoother and generally more comfortable.
What Happens Before You Get Into Position
You’ll change into a hospital gown before the procedure. In the United States, this is typically a knee-length, reusable cloth gown that ties in the back. Some facilities now offer modified garments designed to provide more coverage and reduce the feeling of exposure. Either way, your buttocks will need to be accessible for the procedure, so the gown opens from behind.
You’ll lie down on the exam table and get into the left-side position before sedation begins. A nurse will help you get comfortable and position your legs. Once you’re settled, the IV sedation is administered, and you’ll either drift into a light sleep or become deeply relaxed depending on the type of sedation used. Most people remember very little of the actual procedure.
You May Be Repositioned During the Procedure
While most colonoscopies are completed entirely with you on your left side, the doctor may ask the team to shift you onto your back or onto your right side partway through. This happens for a practical reason: changing your position causes fluid, air, and any remaining debris inside your colon to shift with gravity, revealing areas of the lining that were previously hidden.
Rolling you onto your back or right side is particularly useful when the scope reaches the far end of the colon, called the cecum. If preparation wasn’t perfect and some residual material is obscuring the view, a position change can move that material away and expose tissue that needs to be examined. Studies have found that these mid-procedure position changes improve both the ability to reach the far end of the colon and the detection rate of polyps. You won’t need to do anything yourself during these shifts. The medical team handles the repositioning while you’re sedated.
What If You Have Mobility Limitations
If you have hip problems, back pain, or any musculoskeletal condition that makes lying on your left side difficult, let your doctor’s office know ahead of time. Some patients physically cannot hold the standard position comfortably, and the medical team can plan alternatives. Colonoscopies can be started in other positions, including on the back, though this may require adjustments to the technique. Research has shown that starting in the supine (face-up) position with sedation can slightly increase the risk of drops in oxygen levels, so the team will monitor you more closely if an alternative position is needed.
After the Procedure: Recovery Position
During a colonoscopy, air is pumped into the colon to inflate it and give the doctor a clear view. That air needs to come out afterward, and passing it is the main source of post-procedure discomfort: bloating, pressure, and cramping.
Lying on your left side after the procedure helps with this. Research comparing left-side, right-side, and face-up recovery positions found that patients placed on their left side passed gas more quickly and experienced faster relief from bloating than those in other positions. So the same position you started in turns out to be the best one for recovery, too. Nurses in the recovery area will typically position you this way and encourage you to pass gas freely, which is both expected and welcome.
Most people spend 30 to 60 minutes in recovery before they’re ready to get dressed and leave. The bloating usually resolves within a few hours as the remaining air works its way out. Walking around gently after you get home can also help move things along.