Sigmoidoscopy is a medical procedure that involves inserting a flexible tube approximately one centimeter in diameter (sigmoidoscope) into the anus to observe the internal structures of the rectum and the lower part of the colon. Its primary purpose is to diagnose intestinal diseases, detect early lesions, and perform tissue sampling or minor therapeutic interventions. This examination is commonly used for cancer screening, evaluating symptoms such as bleeding or abdominal pain, and monitoring polyp changes.
This procedure is invasive but relatively safe, usually performed on an outpatient basis without general anesthesia. Prior to the examination, bowel cleansing is required to ensure clear visualization. The physician views real-time images through a camera lens and can perform biopsies or remove small polyps simultaneously, achieving both diagnostic and therapeutic goals.
Sigmoidoscopes are classified into "optical" and "enhanced imaging" types. Optical scopes require direct observation by the physician, while enhanced imaging scopes transmit images to a monitor, with higher resolution being more common. The device's front end is equipped with a light source, camera, and operational channel, which can be extended to reach the rectum and sigmoid colon (approximately 30-60 centimeters long).
The mechanism involves direct visualization of the intestinal mucosa to identify ulcers, tumors, vascular abnormalities, or inflammation. Polyps smaller than 0.5 centimeters can be immediately removed with endoscopic clips, avoiding the need for subsequent surgery. This technique combines diagnosis and treatment, shortening the patient's medical process.
Common indications include:
This examination is also used to assess the activity of inflammatory bowel disease or confirm abnormalities seen on radiological imaging. Patients with suspected intestinal strictures should be evaluated by a physician before the procedure to prevent perforation risks.
Before the procedure, bowel preparation with laxatives is required, usually fasting from solids for 6-8 hours on the day of the exam. The patient lies on their side while the physician slowly inserts the sigmoidoscope into the anus, inflating the bowel as they advance. The entire process lasts approximately 10-20 minutes, during which mild bloating may occur.
If tissue sampling is needed, the physician will use endoscopic forceps to obtain suspected lesion tissues for pathological examination. Some medical facilities offer sedatives to ease anxiety, but these are not anesthetics, allowing patients to resume normal activities shortly after the procedure.
Main advantages include:
Compared to traditional X-ray barium enemas, sigmoidoscopy allows direct mucosal inspection and immediate treatment of lesions. It is less invasive than abdominal surgery and involves no radiation exposure, making it suitable for regular follow-up in high-risk groups.
Potential risks include:
Serious complications include significant bleeding or intestinal perforation. If severe abdominal pain, bloody stools, or fever occur after the procedure, immediate medical attention is necessary. Patients on long-term anticoagulants should adjust their medication to reduce bleeding risks.
Contraindications include:
Proper bowel preparation is essential before the exam; inadequate prep may impair visualization. Diabetic patients should adjust medication timing to prevent hypoglycemia. After the procedure, avoid driving for 24 hours due to residual sedative effects.
Compared to colonoscopy, sigmoidoscopy cannot examine the entire colon, but bowel preparation before and after the procedure is similar. If other invasive procedures (such as tissue biopsies) are performed simultaneously, inform the physician to avoid repeated anesthesia.
Long-term use of NSAIDs (e.g., ibuprofen) may increase the risk of intestinal bleeding; medication should be temporarily stopped or dosage adjusted before the exam. Unlike radiological tests (like CT colonography), sigmoidoscopy allows immediate treatment.
Clinical studies show that regular sigmoidoscopy screening can reduce mortality from left-sided colon cancer by 30-50%. The American Cancer Society recommends screening every 5 years starting at age 50, combined with fecal occult blood testing to improve sensitivity.
For patients with familial adenomatous polyposis, this exam can detect over 90% of polyps, with early removal preventing malignant transformation. Its real-time tissue sampling accuracy reaches up to 95%, making it an important tool for diagnosing inflammatory bowel disease.
Other options include:
If patients refuse invasive procedures due to fear, stool DNA testing or blood markers can be used for initial screening. However, sigmoidoscopy remains the gold standard for diagnosing structural abnormalities in the intestine.
Start a low-fiber diet 24 hours before the exam and take bowel-cleansing medications to empty the intestines. Fasting for 6-8 hours is usually required, but small amounts of water are permitted. Patients should inform their healthcare team in advance if they are on anticoagulants or other specific medications for personalized instructions.
How can common post-exam bloating or abdominal pain be relieved?Mild bloating or discomfort after the exam is normal and can be alleviated by walking to promote gas expulsion. Avoid eating difficult-to-digest foods immediately afterward. If pain persists for more than 4 hours or is accompanied by bleeding or severe diarrhea, seek medical evaluation promptly.
Will abnormal tissue found during the exam be treated immediately?If polyps or other lesions are detected, the physician usually performs immediate biopsy or removal of small polyps using endoscopic forceps. Complex lesions requiring further surgery will be scheduled with a treatment plan and risk explanation provided by the medical team.
When can normal diet and activities resume after the exam?Rest for 1-2 hours after the exam until the effects of anesthesia wear off. Non-anesthetized patients can resume a light diet within hours, but should avoid high-fiber or irritating foods for 24 hours. Usually, daily activities can be resumed the day after the procedure.
Who needs regular sigmoidoscopy screening?Individuals over 50, with a family history of colorectal cancer or polyps, or experiencing abnormal bowel habits or blood in stool, should follow medical advice for regular screening. High-risk groups may need repeat examinations every 1-3 years, with frequency determined by the physician based on individual risk assessment.
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