Last updated: March 2026
What Is a Colonoscopy?
A colonoscopy is a medical procedure that allows a gastroenterologist to examine the entire lining of the colon (large intestine) and rectum using a flexible, lighted instrument called a colonoscope. The colonoscope is a thin, flexible tube equipped with a small camera and light at its tip, which transmits high-definition video to a monitor so the physician can inspect the tissue in real time. Approximately 15 million colonoscopies are performed each year in the United States, making it one of the most widely used and well-studied procedures in gastroenterology.
The primary purpose of a colonoscopy is twofold: screening and diagnosis. As a screening tool, colonoscopy is the gold standard for detecting colorectal cancer and precancerous growths called polyps. As a diagnostic tool, it helps physicians evaluate symptoms such as chronic abdominal pain, rectal bleeding, unexplained changes in bowel habits, and chronic diarrhea. When polyps are found during the procedure, they can usually be removed on the spot, which is the single most effective method for preventing colorectal cancer from developing.
At Texas Gut Health in Sachse, TX, Dr. Jaison John performs colonoscopies with advanced endoscopic equipment in a comfortable outpatient setting. Dr. John completed his gastroenterology fellowship at UT Medical Branch, where he served as Chief Fellow, and his internal medicine residency at UT Austin Dell Medical School, where he served as Chief Resident. He holds dual board certifications from the American Board of Internal Medicine in both internal medicine and gastroenterology.
Who Needs a Colonoscopy?
The American Cancer Society (ACS) and the U.S. Preventive Services Task Force (USPSTF) recommend that all adults at average risk for colorectal cancer begin screening at age 45. This recommendation was updated from age 50 in response to rising rates of colorectal cancer in younger adults. The American College of Gastroenterology (ACG) and the American Gastroenterological Association (AGA) also endorse age 45 as the starting point for average-risk screening.
You may need a colonoscopy before age 45 or more frequently than every 10 years if you have one or more of the following risk factors:
- Family history of colorectal cancer or advanced polyps — A first-degree relative (parent, sibling, or child) diagnosed with colorectal cancer or advanced adenomatous polyps, especially before age 60, significantly increases your risk. Screening should begin at age 40 or 10 years before the age your relative was diagnosed, whichever comes first.
- Personal history of polyps — If a previous colonoscopy found adenomatous or serrated polyps, your gastroenterologist will recommend surveillance colonoscopies at intervals of 1 to 5 years depending on the polyps' size, number, and histology.
- Inflammatory bowel disease (IBD) — Patients with Crohn's disease or ulcerative colitis involving the colon have an elevated lifetime risk of colorectal cancer and should begin surveillance colonoscopies 8 years after their initial diagnosis.
- Hereditary cancer syndromes — Conditions such as Lynch syndrome (hereditary nonpolyposis colorectal cancer) and familial adenomatous polyposis (FAP) require colonoscopy screening beginning in the teens or early twenties.
- Unexplained gastrointestinal symptoms — Symptoms such as persistent rectal bleeding, iron-deficiency anemia, unexplained weight loss, chronic diarrhea or constipation, or a significant change in bowel habits may warrant a diagnostic colonoscopy regardless of age.
If you are a resident of Sachse, Murphy, Wylie, Plano, Garland, Rowlett, Richardson, or anywhere in the Dallas-Fort Worth metroplex and are unsure whether you need a colonoscopy, Dr. John and the team at Texas Gut Health can help you assess your personal risk and determine the appropriate screening schedule.
What to Expect
Understanding what happens before, during, and after a colonoscopy can help ease any anxiety and ensure the best possible outcome. Here is a step-by-step overview of the experience at Texas Gut Health.
Before Your Colonoscopy
Preparation is the most important part of a successful colonoscopy. A clean colon allows your gastroenterologist to see the lining clearly, which is essential for detecting even small polyps and early-stage abnormalities. Our office will provide you with detailed, written prep instructions tailored to your health history. In general, preparation includes:
- Dietary changes: You will follow a clear liquid diet for the entire day before your procedure. Clear liquids include water, broth, clear juices (apple or white grape), plain gelatin (no red or purple colors), and black coffee or tea without cream.
- Bowel prep solution: You will drink a prescribed laxative solution, usually in a split-dose format (half the evening before and half the morning of your procedure). Split-dose preparation has been shown by the ACG to improve colon cleanliness and patient comfort compared to drinking the entire prep the night before.
- Medication adjustments: Inform Dr. John about all medications you take, including blood thinners, diabetes medications, and supplements. Some medications may need to be adjusted or temporarily stopped before the procedure.
- Transportation: Because you will receive sedation, you must arrange for a responsible adult to drive you home after the procedure. You will not be permitted to drive, operate machinery, or make important decisions for the remainder of the day.
During the Procedure
A colonoscopy typically takes 30 to 60 minutes from start to finish. Here is what happens once you arrive at the facility:
- Check-in and preparation: A nurse will confirm your medical history, review your medications, and start an intravenous (IV) line in your arm.
- Sedation: You will receive sedation through your IV, which will make you comfortable and drowsy. Most patients fall into a light, twilight-like sleep and do not feel or remember the procedure.
- The examination: Dr. John will gently insert the colonoscope through the rectum and advance it through the entire length of the colon to the cecum (where the small intestine meets the large intestine). The camera transmits real-time, high-definition images to a monitor, allowing Dr. John to carefully inspect the colon lining as the scope is slowly withdrawn.
- Polyp removal and biopsies: If polyps or suspicious tissue are found, Dr. John will remove them using small instruments passed through the colonoscope. This is painless and adds only a few minutes to the procedure. Tissue samples are sent to a pathology lab for analysis.
After Your Colonoscopy
After the procedure, you will be moved to a recovery area where nurses will monitor you for approximately 30 to 60 minutes as the sedation wears off. Most patients feel alert within 30 minutes, though the full effects of sedation may take several hours to resolve completely.
- Preliminary results: Dr. John will speak with you and your companion before you leave to share initial findings. If biopsies or polyps were taken, pathology results are typically available within 1 to 2 weeks.
- Post-procedure guidelines: You may experience mild bloating or gas as your body expels the air used to inflate the colon during the exam. This is normal and resolves quickly. You can usually resume eating within a few hours, starting with light foods.
- Activity restrictions: Plan to rest for the remainder of the day. Do not drive, drink alcohol, or sign legal documents for 24 hours after receiving sedation.
Conditions Diagnosed or Treated
A colonoscopy can help diagnose, evaluate, or manage a wide range of gastrointestinal conditions. Some of the most common conditions identified through colonoscopy include:
- Colorectal cancer — Colonoscopy is the most effective screening test for colorectal cancer, the third most common cancer diagnosed in both men and women in the United States. Early detection through colonoscopy has contributed to a significant decline in colorectal cancer mortality over the past three decades.
- Colon polyps — Polyps are growths on the lining of the colon that may be benign, precancerous (adenomatous), or, rarely, cancerous. The ability to find and remove polyps during a colonoscopy is what makes the procedure uniquely valuable for cancer prevention.
- Crohn's disease — Colonoscopy with biopsy is a key tool for diagnosing and monitoring Crohn's disease, a chronic inflammatory bowel disease that can affect any part of the digestive tract.
- Ulcerative colitis — Colonoscopy helps confirm a diagnosis of ulcerative colitis, assess the extent and severity of inflammation, and monitor for dysplasia (precancerous changes) in long-standing disease.
- Irritable bowel syndrome (IBS) — While IBS itself does not cause visible changes in the colon, a colonoscopy may be performed to rule out other conditions that mimic IBS symptoms, such as inflammatory bowel disease or microscopic colitis.
- Diverticular disease — Colonoscopy can identify diverticulosis (small pouches in the colon wall) and evaluate patients who have experienced diverticulitis or diverticular bleeding.
- Gastrointestinal bleeding — A colonoscopy can locate the source of rectal bleeding or blood in the stool and, in many cases, treat the bleeding during the same procedure using cauterization or other techniques.
- Anemia — Iron-deficiency anemia with no obvious cause is a common reason for referral for colonoscopy, as it may indicate occult (hidden) bleeding from the colon.
Risks and Benefits
Colonoscopy is widely regarded as a safe and highly effective procedure. Like any medical procedure, it carries a small number of risks that patients should understand before consenting.
Benefits
- Cancer prevention: Colonoscopy is the only colorectal cancer screening method that both detects and prevents cancer in a single procedure by allowing polyp removal during the exam. Studies estimate that colonoscopy with polypectomy reduces colorectal cancer incidence by 40% to 60% and colorectal cancer mortality by 29% to 68%.
- Early detection: Colorectal cancer found at an early, localized stage has a 5-year survival rate of approximately 91%, compared to just 14% when diagnosed at a distant stage, according to the American Cancer Society.
- Comprehensive evaluation: Unlike other screening methods such as stool-based tests or CT colonography, a colonoscopy allows direct visualization of the entire colon and the ability to take action (biopsy or polyp removal) during the same procedure.
- Long screening interval: A normal colonoscopy result in an average-risk patient allows a 10-year interval before the next screening is needed, making it one of the most efficient long-term screening strategies.
Risks
Serious complications from colonoscopy are uncommon. According to large published studies, the overall complication rate for screening colonoscopy is approximately 2.8 per 1,000 procedures. The most significant risks include:
- Bleeding: Minor bleeding may occur at the site of a polyp removal and usually resolves on its own. Significant bleeding requiring intervention occurs in roughly 1 in 1,000 colonoscopies with polypectomy.
- Perforation: A tear in the colon wall is rare, occurring in approximately 1 in 1,500 to 1 in 2,000 colonoscopies. If a perforation occurs, it may require hospitalization or, in rare cases, surgical repair.
- Adverse reaction to sedation: Complications from sedation (such as respiratory depression or an allergic reaction) are infrequent and are monitored for by the anesthesia team throughout the procedure.
- Post-polypectomy syndrome: Occasionally, patients may experience localized abdominal pain, fever, or elevated white blood cell count after polyp removal. This usually resolves with conservative treatment.
Dr. John discusses all risks and benefits with each patient during the pre-procedure consultation. The overwhelming medical consensus, as affirmed by the ACG, AGA, and USPSTF, is that the benefits of colonoscopy for colorectal cancer prevention far outweigh the small risks of the procedure for eligible patients.
When to Seek Immediate Care
Contact Texas Gut Health immediately at (214) 624-6596 or go to your nearest emergency room if you experience any of the following after your colonoscopy: severe or worsening abdominal pain, persistent rectal bleeding or passage of large blood clots, fever above 100.4°F (38°C), dizziness or fainting, or inability to pass gas or have a bowel movement for more than 24 hours after the procedure. While serious complications are rare, prompt medical evaluation is essential if any of these symptoms occur.