colonoscopy

colonoscopy
Name	Colonoscopy
MeshID	D003113
MedlinePlus	003886

colonoscopy. A colonoscopy is a diagnostic and therapeutic endoscopic procedure that allows for the direct visualization of the lining of the large intestine and the distal part of the small intestine. It is considered the gold standard for the detection of colorectal cancer and is a critical tool in the field of gastroenterology. The procedure is typically performed by a gastroenterologist in an outpatient setting, such as a hospital or an ambulatory surgery center.

Procedure

The examination is conducted using a colonoscope, a flexible tube equipped with a light and a camera, which is inserted through the anus. The physician advances the instrument through the rectum and into the colon, often reaching the cecum and sometimes the terminal ileum. During the procedure, the bowel is insufflated with carbon dioxide or air to provide better visualization. Key maneuvers include torque steering and loop reduction, techniques refined by pioneers like William I. Wolff and Hiromi Shinya. If abnormalities are found, the physician can perform interventions such as a polypectomy using a snare or obtain biopsy samples for histopathology. The entire process is usually monitored on a video screen, and the patient is often under conscious sedation administered by an anesthesiologist.

Indications

Common reasons for referral include screening for colorectal cancer as recommended by organizations like the American Cancer Society, investigation of symptoms such as rectal bleeding or unexplained iron deficiency anemia, and surveillance in patients with a history of adenomatous polyps or inflammatory bowel disease like Crohn's disease or ulcerative colitis. It is also indicated for the evaluation of abnormal findings on imaging studies such as a CT colonography or a positive fecal immunochemical test. Patients with a strong family history of Lynch syndrome or familial adenomatous polyposis undergo regular surveillance.

Risks and complications

While generally safe, the procedure carries a small risk of serious adverse events. The most common complication is perforation of the colon, which may require immediate surgical repair, often involving a colectomy. Significant bleeding can occur, particularly after a polypectomy, sometimes necessitating angiography or a return to the operating room. Reactions to sedatives, such as respiratory depression, are managed by the anesthesia team. Other rare risks include post-polypectomy electrocoagulation syndrome, infection, and complications related to underlying conditions like diverticulitis. The overall rate of major complications remains low, as documented in studies from the Cleveland Clinic and Mayo Clinic.

Preparation

Adequate bowel cleansing, or bowel preparation, is essential for a successful examination. This typically involves a clear liquid diet for 24 hours prior and the ingestion of a lavage solution, such as polyethylene glycol, often branded as GoLYTELY. Split-dose regimens, where half is taken the night before and half the morning of the procedure, are now standard, as endorsed by the American Society for Gastrointestinal Endoscopy. Patients are usually instructed to stop taking certain medications, like anticoagulants including warfarin or clopidogrel, following guidelines from their cardiologist or primary care physician. Failure to achieve a clean colon, as graded by the Boston Bowel Preparation Scale, can significantly reduce the adenoma detection rate.

Results and follow-up

Findings are documented using standardized terminology like the Paris classification for polyps. If no abnormalities are found, the next screening interval is typically in ten years for average-risk individuals, per guidelines from the U.S. Preventive Services Task Force. The discovery of adenomas dictates surveillance intervals based on the number, size, and histology reported by the pathology department, following the Multi-Society Task Force recommendations. The removal of sessile serrated lesions also warrants specific follow-up. For findings of colorectal cancer, a referral to an oncologist and a surgeon is made for staging and treatment, which may include chemotherapy or radiation therapy.

Alternatives

Several other modalities exist for evaluating the colon. CT colonography, also known as virtual colonoscopy, uses computed tomography scanning and is less invasive but cannot remove polyps. Flexible sigmoidoscopy, often promoted by programs like NHS England, examines only the distal colon. Stool-based tests, such as the fecal immunochemical test or the multi-target Cologuard test, are non-invasive screening options. For direct visualization without sedation, capsule endoscopy devices like the PillCam COLON can be used, though they are not widely adopted for primary screening. The choice of alternative depends on patient preference, risk factors, and local availability, as outlined by the European Society of Gastrointestinal Endoscopy.

Category:Endoscopy Category:Gastroenterology Category:Medical procedures