Flexible endoscopes equipped with video cameras can be used to view the upper GI tract from pharynx to upper duodenum and the lower GI tract from anus to cecum (and, sometimes, terminal ileum). Several other diagnostic and therapeutic interventions also can be done endoscopically. The potential to combine diagnosis and therapy in one procedure gives endoscopy a significant advantage over studies that provide only imaging (eg, x-ray contrast studies, CT, MRI) and often outweighs endoscopy’s higher cost and need for sedation.
Endoscopy generally requires IV sedation and, for upper endoscopy, topical anesthesia of the throat. Exceptions are anoscopy and sigmoidoscopy, which generally require no sedation. The overall complication rate of endoscopy is 0.1 to 0.2%; mortality is about 0.03%. Complications are usually drug related (eg, respiratory depression); procedural complications (eg, aspiration, perforation, significant bleeding) are less common.
Diagnostic procedures by conventional endoscopy include cell and tissue sample collection by brush or biopsy forceps. Several different types of endoscopes provide additional diagnostic and therapeutic functions. Ultrasound-equipped endoscopes can evaluate blood flow or provide imaging of mucosal, submucosal, or extraluminal lesions. Endoscopic ultrasound can provide information (eg, the depth and extent of lesions) that is not available via conventional endoscopy. Also, fine-needle aspiration of both intraluminal and extraluminal lesions can be done with endoscopic ultrasound guidance. Conventional endoscopes cannot visualize the vast majority of the small intestine. Push enteroscopy uses a longer endoscope that can be manually advanced into the distal duodenum or proximal jejunum.
Balloon-assisted enteroscopy provides additional assessment of the small intestine beyond push enteroscopy. It uses an endoscope with one or two inflatable balloons attached to an overtube fitted over the endoscope. When the endoscope is advanced to the farthest possible distance, the balloon is inflated and anchored to the intestinal mucosa. Pulling back of the inflated balloon pulls the small bowel over the overtube like a sleeve, thus shortening and straightening the small intestine and allowing further advancement of the endoscope. Balloon-assisted enteroscopy can be done in anterograde (caudad) or retrograde (cephalad) fashion, enabling examination of the entire small intestine.
Screening colonoscopy is recommended for patients at high risk of colon cancer and for everyone ≥ 50 yr. Colonoscopy should be done every 10 yr for patients with no risk factors or history of polyps. CT colonography (see X-Ray and Other Imaging Contrast Studies of the GI Tract : CT colonography) is an alternative to colonoscopy for screening for colonic tumors.
Therapeutic endoscopic procedures include
Removal of foreign bodies
Hemostasis by hemoclips placement, injection of drugs, thermal coagulation, laser photocoagulation, variceal banding, or sclerotherapy
Debulking of tumors by laser or bipolar electrocoagulation
Ablative therapy of premalignant lesions
Dilation of webs or strictures
Reduction of volvulus or intussusception
Decompression of acute or subacute colonic dilation
Feeding tube placement
Absolute contraindications to endoscopy include
Relative contraindications include poor patient cooperation, coma (unless the patient is intubated), and cardiac arrhythmias or recent myocardial ischemia.
Patients taking anticoagulants or chronic NSAID therapy can safely undergo diagnostic endoscopy. However, if there is a possibility that biopsy or photocoagulation will be done, these drugs should be stopped for an appropriate interval before the procedure. Oral iron-containing drugs should be stopped 4 to 5 days before colonoscopy, because certain green vegetables interact with iron to form a sticky residue that is difficult to remove with a bowel preparation and interferes with visualization. The American Heart Association no longer recommends endocarditis prophylaxis for patients having routine GI endoscopy.
Routine preparations for endoscopy include no solids for 6 to 8 h and no liquids for 4 h before the procedure. Additionally, colonoscopy requires cleansing of the colon. A variety of regimens may be used, but all typically include a full or clear liquid diet for 24 to 48 h and some type of laxative, with or without an enema. A common laxative preparation involves having the patient drink a high-volume (4 L) balanced electrolyte solution over a period of 3 to 4 h before the procedure. Patients who cannot tolerate this solution may be given magnesium citrate, sodium phosphate, polyethylene glycol, lactulose, or other laxatives. Enemas can be done with either sodium phosphate or tap water. Phosphate preparations should not be used in patients with renal insufficiency.
In video capsule endoscopy (wireless video endoscopy), patients swallow a capsule containing a camera that transmits images to an external recorder. This noninvasive technology provides diagnostic imaging of the small bowel that is otherwise difficult to obtain by conventional endoscopies. This procedure is particularly useful in patients with occult GI bleeding and for detection of mucosal abnormalities. Capsule endoscopy is more difficult in the colon and is, therefore, not an adequate modality for colorectal cancer screening.