Colorectal Cancer Diagnosis

Clear liquid diets, giant containers of prep solution, heightened nerves, and spending the majority of an evening tied to your toilet—it’s no wonder that for many people, the toughest part of a colonoscopy isn’t the procedure itself: it’s the preparation.

As a gastroenterologist, colorectal cancer screening is one of my most important tasks. However, a colonoscopy is really a partnership. Your care team doesn’t do all the work; you do much of that work ahead of time.

I’m sharing some of the best tips I’ve learned for making that prep process easier.

Know your ‘why’

While prep can be unpleasant, it can be helpful to understand exactly why you need to prep for a colonoscopy in the first place.

Colonoscopies are the best colorectal cancer screening method. They can help your care team find and detect colorectal cancer at an earlier stage when it is easier to treat. But colorectal cancer isn’t the only thing your doctor looks for when performing a colonoscopy.

This procedure allows your doctor to see anything abnormal in your colon. This includes:

• Colorectal cancer
• Polyps, or abnormal growth in the colon’s lining. Polyps may be benign or may grow into colon cancer if they aren’t removed. If your doctor finds polyps, he/she will remove them during a colonoscopy and send them to a lab for testing.
• Inflammation
• Ulcers
• Bacterial or viral infections
• Diverticula
• Hemorrhoids

During a colonoscopy, a gastroenterologist uses a scope to take a close look at the inside of your colon. The inside of a colon looks like a collapsed tube sock, so during a colonoscopy, your doctor will use air to stretch out the colon so they can examine between any folds and crevices.

For a doctor to get a good look at your colon, it needs to be clean. Just like how a dirty window makes it harder to get a clear view, stool and food material can make it harder for your doctor to get a clear look at every part of your colon.

Start preparing early

Preparing for the colonoscopy is very similar to following a recipe. You usually want to check the recipe before the day you're going to cook the meal. This ensures you have all the ingredients, understand the directions and know how long the process will take.

If you wait until the day before your colonoscopy to prepare, it may be too late. Instead, set aside time a week before your procedure to read the instructions, pick up your prep and ensure you have all the medications you will need.

If you follow the prep instructions, getting a colonoscopy usually isn't as bad as what you may have heard. I think sometimes the hype is a little worse than the actual experience. Usually, people wake up from their procedures with me saying, “Wow, that wasn't that bad!”

Eat a low-fiber diet the week before your colonoscopy

A week before your colonoscopy is a good time to start a low-fiber diet. While fiber is good for you, it can stick around your colon and gastrointestinal tract. That’s why you should avoid high-fiber foods such as raw vegetables and salads starting a week before your procedure.

Stick to a clear liquid diet the day before your colonoscopy

Follow a clear liquid diet the day before your procedure. While the term ‘clear liquid diet’ might sound like it only includes water and broth, it includes anything that you could put into a glass dish and still read a newspaper underneath. For example, you can eat and drink options like:

• Black coffee
• Sports drinks
• Jell-O
• Broth that doesn’t contain anything fibrous like rice, bread or vegetables.

Avoid food and drinks with red, orange and purple food coloring

Steer clear of eating or drinking anything with red, orange or purple food coloring the day before your procedure. This is because, sometimes, it can be hard for your care team to tell the difference between these reddish food dyes in your colon and something like blood or inflammation.

Foods and drinks with green or blue coloring are totally fine before a colonoscopy. If I see green in your colon, for example, I won’t confuse it with blood. It’s more of a concern for those reddish colors.

Don’t drink your prep all at once

There are different varieties and flavors of colonoscopy prep, but they all work in a similar way. Your prep will contain some type of salt that you mix with a lot of water.

A common misconception about the prep solution is that you are supposed to drink it all at once. Instead, we recommend a more effective way to clean your colon called split-dose prep. This means drinking half of the prep the night before your procedure, usually within about a two-hour window.

Save the other half of the prep for the morning of your procedure. Usually, we aim to have patients finish their second half of the prep about four hours before their scheduled colonoscopy.

Chill your prep solution

One easy way to make your prep taste better? Drink it cold. Lukewarm prep in a jug that's been sitting out is going to taste much worse than if it's ice cold.

If the jug is too big to fit in your fridge, fill a thermos with ice and pour your prep into it as you drink it.

Use a straw to drink your prep

Using a straw can block some of the prep’s flavor and make drinking your prep quicker. Win-win!

Flavor your prep your way

Some prep solutions come with a flavoring packet. While these flavoring packets may make your prep taste better, they don’t make your prep work any better.

You don’t need to use the flavoring packet that comes with your prep. Instead, you can go without or use another option like flavored electrolytes or lemonade packets – just be sure to avoid options with red food dye.

One perk of using electrolyte packets is that they can help you stay hydrated. Prepping for a colonoscopy means drinking lots of fluid – and flushing lots of fluid out of your body. Electrolyte packets can help you stay hydrated without having to drink even more water.

Put a menthol candy under your tongue while drinking prep

One lesser-known tip for getting through your prep? Place a menthol candy under your tongue to block the prep’s taste. Just remember to choose an option without red, orange or purple food dye.

Remember the bigger picture

The lead-up to your colonoscopy can feel more inconvenient than the actual procedure.

A colonoscopy is relatively quick. In total, the procedure only takes about a half hour to 40 minutes. Most of that time, you’ll be asleep under anesthesia. A colonoscopy is also painless since you don't have any nerves in your colon. So, even getting polyps removed doesn’t hurt. You wake up completely unmindful of the procedure; the most you might feel is a little gassy due to the air used to stretch out the colon.

While the procedure itself is painless, the prep can be uncomfortable for some people.

The good news? Usually, you don't have to do it all that frequently. If you are at average risk for colorectal cancer, you should get a colonoscopy every 10 years starting at age 45. If polyps are found during a colonoscopy, you may need another colonoscopy a little sooner.

But if we don’t find anything or the findings are benign, you only need a colonoscopy every 10 years. We strive to give you a high-quality exam every time so that we don’t have to repeat your colonoscopy more often than necessary. A better prep leads to a higher quality exam, so it’s worth it to follow the instructions.

Request an appointment at MD Anderson online or call 1-877-632-6789.

The sigmoid colon is the part of the large intestine (colon) closest to the rectum. It absorbs water from stool and pushes the stool to the rectum and anus until it’s ready to be expelled when you use the bathroom.

Colorectal cancer is an umbrella term for colon cancer and rectal cancer. Studies have shown that colorectal cancer is more common in the sigmoid colon, which is on the left side, along with the descending colon and rectum. The rectum is also considered the left side even though it’s not part of the colon.

Gastrointestinal medical oncologist Kanwal Raghav, M.D., estimates that about 70% of colorectal cancers are diagnosed on the left side.

“It’s unclear why colon cancer starts in a particular location, although some explanations exist,” says Raghav. “However, left-side colon cancers are more common than right-side colon cancers.”

The colon starts at the cecum, which is on the right side. It goes up to the ascending colon, across the body to the transverse colon and down to the descending colon and sigmoid colon, which are on the left side.

We spoke with Raghav to learn more about the differences between left-side and right-side colon cancer. Here’s what he shared.

It’s common for left-side tumors to cause symptoms.

It's common for people with left-side colorectal cancer to have changes in their bowel habits or blood in their stool. People with right-side tumors often show fewer symptoms.

Left-side tumors and right-side tumors have different genetic characteristics.

Tumors that develop on the left side of the colon have more mutations of tumor-suppressing genes, like APC and TP53. These genes help prevent tumors from growing. Mutations in these genes make you more likely to develop certain cancers, including colon cancer.  

Tumors that develop on the right side of the colon are more likely in people who have hereditary cancer syndromes. These include high microsatellite instability (MSI-high) – also referred to as DNA mismatch repair deficiency (dMMR) – and Lynch syndrome.

Left-side tumors are easier to detect during a colonoscopy.

During a colonoscopy, your doctor examines the walls and lining of your colon by inserting a flexible scope into your rectum and around your large intestine. Doctors examine the left side first since it’s closer to where the scope is inserted. Colorectal cancer usually starts as a polyp in the colon or rectum.

Left-side tumors often present as polypoid lesions, which protrude into the lumen of the gastrointestinal tract and are easier to see. Colonoscopies are good at detecting these polyps, which is why getting this routine screening is so important.

Many polyps on the right side of the colon are sessile serrated adenomas. These are flat and harder to detect during a colonoscopy. Because of this, right-side colon cancers are often diagnosed at advanced stages and may be harder to treat.

Colonoscopy prep is important because your colon will need to be completely clean of any stool, so your doctor can easily see both the left and right side of your colon.

The side on which cancer develops helps determine your treatment.

Overall, left-side tumors have a better prognosis than right-side tumors. This is because colon cancer on the left side responds better to chemotherapy and targeted therapies, like anti-EGFR and HER2 drugs.

Right-side tumors tend to have more genetic mutations, which are often associated with more aggressive cancers. Right-side tumors are also harder to detect, so they’re often diagnosed when the disease is more advanced. Recently, immunotherapy has been effective in treating these cancers because the body can recognize the abnormal cells and attack them. Immunotherapy has helped improve the prognosis for patients with stage IV right-side colon cancer.

Your doctor and care team will work together to develop the best treatment plan for you. 

Knowledge of left-side and right-side colon cancer leads to treatment advances.

We’ve been treating colorectal cancer for a long time. But only in the last four or five years have we really started to understand the differences between colon cancer that develops on the left side versus the right side. Before then, it wasn’t as commonly acknowledged.

Over the years, we have learned that colon cancer can’t be viewed as one disease. We’re now looking at it as a complex disease with many subtypes and trying to develop targeted and personalized therapies that can be used depending on the specific type people have. Slowly and steadily, we are moving the bar for personalized therapy in colorectal cancer. And I think the location of the cancer – left side versus right side – is a part of that. 

Request an appointment at MD Anderson online or call 1-877-632-6789.