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Lower GI Procedure · Katy & Cypress
Flexible Sigmoidoscopy in Katy & Cypress, TX
Flexible sigmoidoscopy is a short outpatient exam of the rectum and the lower part of the colon using a thin, flexible camera. At United Gastroenterology Associates, PLLC, it is performed by Muhammad Ali Khan, MD, FACP, FASGE, a board-certified gastroenterologist, to evaluate rectal bleeding, diarrhea, inflammation and other lower-bowel problems for patients from Katy, Cypress and Greater Houston. Most patients need only an enema beforehand, and sedation is usually not required.
Lower GI evaluation with Dr. Muhammad Ali Khan
Meet Your Sigmoidoscopy Doctor: Muhammad Ali Khan, MD, FACP, FASGE
BOARD-CERTIFIED Gastroenterologist and Hepatologist
CREDENTIALS AT A GLANCE
Board-Certified
Gastroenterology, hepatology, and internal medicine
Academic Medicine
Former Associate Professor, UT MD Anderson Cancer Center
Published Research
More than 100 peer-reviewed articles in gastroenterology
FACP and FASGE
Fellow, American College of Physicians and American Society for Gastrointestinal Endoscopy
“My gastroenterology & hepatology practice is dedicated to working closely with you to develop a personalized treatment plan that meets your unique needs and preferences.”
Dr. Muhammad Ali Khan, MD, FACP, FASGE
Board-certified gastroenterologist and hepatologist, United Gastroenterology Associates
Flexible sigmoidoscopy at United Gastroenterology Associates is performed by Dr. Khan, a gastroenterologist board-certified in gastroenterology, hepatology and internal medicine and a Fellow of the American Society for Gastrointestinal Endoscopy (FASGE). He also performs colonoscopy, so if your exam shows something that needs a closer look, the next step stays with the same physician.
Dr. Khan is a former Associate Professor at The University of Texas MD Anderson Cancer Center and has authored more than 100 peer-reviewed publications.
Related areas of care
- Rectal bleeding and blood in the stool
- Ulcerative colitis and proctitis
- Chronic diarrhea
- Hemorrhoids and anal fissures
- Colon polyps and colorectal cancer screening
What Is Flexible Sigmoidoscopy?
Flexible sigmoidoscopy is a procedure in which a gastroenterologist passes a thin, flexible tube with a light and camera (a sigmoidoscope) through the anus to examine the rectum and lower colon. It lets the doctor see the lining directly, take small tissue samples (biopsies) and, in many cases, remove small polyps in the area examined.
The exam covers the rectum and the sigmoid colon, and sometimes part of the descending colon. That makes it useful for symptoms that are likely to start low in the bowel, but it does not show the upper and right side of the colon. When the whole colon needs to be seen, a colonoscopy is used instead.
Because the bowel preparation is lighter and sedation is usually not needed, flexible sigmoidoscopy is quicker and simpler than colonoscopy for the right patient. Dr. Khan decides which exam fits your symptoms, history and screening needs.
Flexible sigmoidoscopy at a glance
- Area examined: rectum and lower colon
- Typical prep: one or two enemas before the exam
- Sedation: usually not needed
- Exam time: about 10 to 20 minutes
- During the exam: biopsies and small polyp removal are possible
- Afterward: most people resume normal activities the same day
Your own preparation and timing instructions come from the office and may differ.
Board-Certified Gastroenterologist
Gastroenterology, hepatology and internal medicine
Fellow, ASGE
American Society for Gastrointestinal Endoscopy
Short Outpatient Exam
Usually 10 to 20 minutes, often without sedation
Two Locations
Offices in Katy and Cypress
Why Is Flexible Sigmoidoscopy Performed?
Flexible sigmoidoscopy is mainly used to find the cause of symptoms that point to the rectum or lower colon. Bright red rectal bleeding is one of the most common reasons, since hemorrhoids, fissures, inflammation and polyps in this area can all bleed.
It is also used to look for inflammation in people with ongoing diarrhea, and to check the extent and activity of ulcerative colitis or proctitis without a full bowel preparation. Biopsies taken during the exam help confirm a diagnosis.
Flexible sigmoidoscopy is one of the colorectal cancer screening options accepted by the U.S. Preventive Services Task Force for average-risk adults, but colonoscopy and stool-based tests are used more often. Learn more about colorectal cancer screening options.
Common reasons for the exam
- Bright red blood on toilet paper or in the bowl
- Diarrhea that lasts weeks or keeps returning
- Monitoring ulcerative colitis or proctitis
- Rectal pain or a recent change in bowel habits
- Abnormal imaging or exam findings in the lower colon
- Screening, when chosen with your doctor
A symptom alone does not confirm a diagnosis. Symptoms should be evaluated by a qualified medical professional.
Flexible Sigmoidoscopy vs. Colonoscopy
Both exams use a flexible camera, but they differ in how much of the colon they examine, how you prepare and whether you need sedation. A flexible sigmoidoscopy examines only the rectum and lower colon, while a colonoscopy examines the entire colon and can find and remove polyps anywhere in it.
| Feature | Flexible sigmoidoscopy | Colonoscopy |
|---|---|---|
| Area examined | Rectum and lower colon (sigmoid colon, sometimes part of the descending colon) | Rectum and the entire colon |
| Typical preparation | One or two enemas before the exam; sometimes a laxative or clear liquids | A full bowel prep and clear-liquid diet the day before |
| Sedation | Usually none | Usually sedation or anesthesia |
| Exam time | About 10 to 20 minutes | About 30 to 60 minutes |
| Driving afterward | Usually possible if no sedation was given | Not until the next day; an adult driver is required |
| Biopsy and polyp removal | Possible in the area examined | Possible throughout the colon |
| Screening interval (average risk, USPSTF) | Every 5 years, or every 10 years with a yearly FIT | Every 10 years if results are normal |
| If something is found | A colonoscopy is usually recommended to check the rest of the colon | Most findings can be sampled or removed during the same exam |
Which exam is right depends on your symptoms, age and history. Anemia, black stools, a positive stool test, a family history of colorectal cancer or bleeding without a clear source usually call for a full colonoscopy. If you are due for one, see colonoscopy in Katy or colonoscopy in Cypress.
Questions About a Lower-Colon Exam?
Dr. Khan can review your symptoms and tell you whether flexible sigmoidoscopy, colonoscopy or another test makes the most sense. New patients are welcome at both offices.
How to Prepare and What Happens During the Exam
Preparation for flexible sigmoidoscopy is simpler than for colonoscopy. Always follow the specific instructions the office gives you, because they may differ from this overview.
Review your instructions and medicines
Tell the team about blood thinners, diabetes medicines, iron supplements and any allergies. Do not stop a prescription medicine unless your doctor tells you to.
Clear the lower bowel
Most patients use one or two enemas shortly before the exam, as instructed. Some are also asked to take a laxative or follow a clear-liquid diet.
The exam
You lie on your left side while Dr. Khan gently passes the sigmoidoscope. Air or carbon dioxide opens the colon, which can cause pressure or cramping. Biopsies, if needed, are painless.
Recovery
Bloating or cramping usually settles within an hour or two. Unless you were sedated, you can usually eat, drive and return to normal activities the same day.
Results
Dr. Khan can describe what he saw right after the exam. If biopsies were taken, pathology results usually take several days, and the office will follow up with you.
Is Flexible Sigmoidoscopy Safe?
Flexible sigmoidoscopy is a common, low-risk procedure. Possible complications include bleeding, especially after a biopsy or polyp removal, and, rarely, a tear (perforation) in the bowel wall. Mild cramping and passing gas afterward are normal and expected.
Call the office or seek emergency care after the exam if you have:
- Severe or worsening abdominal pain
- Heavy rectal bleeding or more than a few teaspoons of blood
- Fever or chills
- Dizziness or feeling faint
Insurance and Self-Pay Options
United Gastroenterology Associates participates with many major insurance plans. Coverage and benefits depend on your specific plan and must be verified, and coverage for a procedure can differ depending on whether it is done for screening or to evaluate symptoms. Please contact the office or your insurance carrier to verify benefits for your specific plan and service.
Flexible Sigmoidoscopy FAQs
Answers to common questions about flexible sigmoidoscopy at United Gastroenterology Associates.
Where can I get a flexible sigmoidoscopy in Katy or Cypress?
United Gastroenterology Associates offers flexible sigmoidoscopy for patients seen at its Katy office (23920 Katy Freeway, Suite 555) and Cypress office (21216 Northwest Freeway, Suite 640). Dr. Muhammad Ali Khan evaluates you first and explains where and when the exam will be done. Call (346) 340-4414 to schedule.
Can flexible sigmoidoscopy be used to evaluate rectal bleeding?
Yes. Bright red rectal bleeding often comes from the rectum or lower colon, which this exam examines directly. It can show hemorrhoids, fissures, inflammation or polyps. If the source is not found, or if you have anemia, black stools or other risk factors, a full colonoscopy is usually recommended.
Do I need a colonoscopy or a flexible sigmoidoscopy?
It depends on your symptoms and history. Flexible sigmoidoscopy suits problems that are likely to be in the rectum or lower colon, such as monitoring proctitis. A colonoscopy is preferred when the whole colon needs to be seen, for example with anemia, a positive stool test, a family history of colorectal cancer or bleeding without a clear source.
Is flexible sigmoidoscopy painful?
Most people feel pressure, fullness or cramping while air or carbon dioxide opens the colon, but the exam is short and the discomfort usually passes quickly. Taking biopsies is not painful. Tell the team if you are anxious, because sedation can be discussed in some cases.
How long does a flexible sigmoidoscopy take?
The exam itself usually takes about 10 to 20 minutes. Allow extra time for check-in, preparation and a short recovery period afterward.
Can I drive after a flexible sigmoidoscopy?
If you do not receive sedation, you can usually drive and return to normal activities the same day. If sedation is used, you will need an adult to drive you home, and you should not drive until the next day.
Can flexible sigmoidoscopy detect colon cancer?
It can find polyps and cancers in the rectum and lower colon, and polyps can often be sampled or removed during the exam. It cannot see the upper parts of the colon, so it does not replace a colonoscopy when the whole colon needs to be examined.
Flexible Sigmoidoscopy Near Katy and Cypress
Dr. Khan sees patients for lower GI evaluations at both offices of United Gastroenterology Associates, serving Katy, Cypress, Fulshear, Richmond, Rosenberg and communities throughout Greater Houston.
United Gastroenterology Associates – Katy
Katy Freeway (I-10) near the Grand Parkway
- Address: 23920 Katy Freeway, Suite 555, Katy, TX 77494
- Phone: (346) 340-4414
- Hours: Monday–Friday, 8:30 AM–5:00 PM (closed 12:00–1:30 PM for lunch; last appointment 4:30 PM)
United Gastroenterology Associates – Cypress
Northwest Freeway (US-290) in Cypress
- Address: 21216 Northwest Freeway, Suite 640, Cypress, TX 77429
- Phone: (346) 340-4414
- Hours: Monday–Friday, 8:30 AM–5:00 PM (closed 12:00–1:30 PM for lunch; last appointment 4:30 PM)
Schedule a Flexible Sigmoidoscopy Consultation
If you have rectal bleeding, ongoing diarrhea or a condition that needs monitoring, Dr. Khan can evaluate you and recommend the right exam. Call (346) 340-4414 or request an appointment online.
Sources
- National Institute of Diabetes and Digestive and Kidney Diseases. Flexible Sigmoidoscopy. niddk.nih.gov
- National Institute of Diabetes and Digestive and Kidney Diseases. Colonoscopy. niddk.nih.gov
- U.S. Preventive Services Task Force. Colorectal Cancer: Screening (2021). uspreventiveservicestaskforce.org
This page provides general educational information and does not replace medical advice, diagnosis or treatment. Follow the preparation instructions provided by your physician. For a medical emergency, call 911. Last updated October 5, 2026.