Skip to Content



Jonathan Gotfried

, MD, Lewis Katz School of Medicine at Temple University

Last full review/revision Apr 2021| Content last modified Apr 2021

Flexible endoscopes equipped with video cameras can be used to view the upper gastrointestinal tract from pharynx to proximal duodenum and the lower gastrointestinal 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. 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.

Other complications, including myocardial infarction, stroke, and serious pulmonary events, after screening or surveillance colonoscopy are low and no higher than after other low-risk procedures (eg, joint injection or aspiration, lithotripsy, arthroscopy, carpal tunnel or cataract surgery; 1, 2).

General references

  • 1. Wang L, Mannalithara A, Singh G, et al: Low rates of gastrointestinal and non-gastrointestinal complications for screening or surveillance colonoscopies in a population-based study. Gastroenterology 154(3):540–555, 2018. doi: 10.1053/j.gastro.2017.10.006
  • 2. Vargo, JJ 2nd: Sedation-related complications in gastrointestinal endoscopy. Gastrointest Endosc Clin N Am 25(1):147–158, 2015. doi: 10.1016/j.giec.2014.09.009

Diagnostic gastrointestinal endoscopy

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 and potential therapeutic intervention of the entire small intestine.

Screening colonoscopy is recommended for patients at high risk of colon cancer and for everyone ≥ age 50. Recently, some groups have advocated lowering the screening age for colorectal cancer to 45 in response to the rising incidence of early-onset (age < 50) colorectal cancer. Colonoscopy should be done every 10 years for patients with no risk factors or history of polyps and at earlier intervals if polyps are found (1). For more information about colorectal cancer screening recommendations, see screening tests for colorectal cancer.

Colonoscopy screening reference

  • 1. Gupta S, Lieberman D, Anderson JC, et al: Recommendations for follow-up after colonoscopy and polypectomy: A consensus update by the US Multi-Society Task Force on Colorectal Cancer. Gastrointest Endosc 91(3):463–485.e5, 2020. doi: 10.1016/j.gie.2020.01.014

Therapeutic gastrointestinal endoscopy

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
  • Mucosal and/or submucosal tissue resection
  • Dilation of webs or strictures
  • Stent placement
  • Reduction of volvulus or intussusception
  • Decompression of acute or subacute colonic dilation
  • Feeding tube placement
  • Drainage of pancreatic cysts
  • Endoscopic bariatric procedures (eg, placement of intragastric balloons, endoscopic sleeve gastrectomy)
  • Endoscopic myotomy (eg, for esophageal achalasia, refractory gastroparesis)
  • Transoral incision-less fundoplication

Contraindications to gastrointestinal endoscopy

Absolute contraindications to endoscopy include

  • Shock
  • Acute myocardial infarction
  • Peritonitis
  • Acute perforation
  • Fulminant colitis

Relative contraindications include poor patient cooperation, coma (unless the patient is intubated), and cardiac arrhythmias or recent myocardial ischemia.

Patients taking anticoagulants or chronic nonsteroidal anti-inflammatory drug therapy can safely undergo diagnostic endoscopy. However, if there is a possibility that biopsy or photocoagulation will be done, anticoagulants should be stopped for an appropriate interval before the procedure (1). 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 and American College of Cardiology no longer recommend endocarditis prophylaxis for patients having routine gastrointestinal endoscopy (see the guideline for the management of patients with valvular heart disease). The American Society for Gastrointestinal Endoscopy also recommends against antibiotic prophylaxis before any gastrointestinal procedures in patients with synthetic vascular grafts or other nonvalvular cardiovascular devices (eg, implantable electronic devices) or for patients with an orthopedic prosthesis (2). However, antibiotics are used before placement of a percutaneous endoscopic gastrostomy (PEG) tube to prevent site infection and may benefit peritoneal dialysis patients before colonoscopy.

Contraindications references

  • 1. Acosta RD, Abraham NS, Chandrasekhara V, et al: The management of antithrombotic agents for patients undergoing GI endoscopy. Gastrointest Endosc 83(1):3–16, 2016. doi: 10.1016/j.gie.2015.09.035. Clarification and additional information. Gastrointest Endosc 83(3):678, 2016.
  • 2. ASGE Standards of Practice Committee, Khashab MA, Chithadi KV, et al: Antibiotic prophylaxis for GI endoscopy. Gastrointest Endosc 81(1):81–89, 2015. doi: 10.1016/j.gie.2014.08.008

Preparation for gastrointestinal endoscopy

Routine preparations for endoscopy include no solids for 8 hours and no liquids for 2 to 4 hours before the procedure (see the American Society of Anesthesiologists Task Force's guidelines on preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration). 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 hours and some type of laxative, with or without an enema (1). Bowel cleansing preparations using a high volume of an electrolyte-containing liquid are commonly used. The preparations are available in different volumes (ranging between 2 L and 4 L) and have varying degrees of efficacy. Giving preparations in a split-dose fashion, ie, giving half the volume the day before the procedure and half the volume the day of the procedure, has been shown to improve patient compliance, examination quality, and adenoma detection rate (2). Patients who cannot tolerate these preparations 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.

Preparation references

  • 1. Gu P, Lew D, Oh SJ, et al: Comparing the real-world effectiveness of competing colonoscopy preparations: Results of a prospective trial. Am J Gastroenterol 114(2):305–314, 2019. doi: 10.14309/ajg.0000000000000057
  • 2. ASGE Standards of Practice Committee, Saltzman JR, Cash BD, et al: Bowel preparation before colonoscopy. Gastrointest Endosc 81(4):781–794, 2015. doi: 10.1016/j.gie.2014.09.048

Video capsule endoscopy

In video capsule endoscopy (wireless video endoscopy), patients swallow a disposable capsule containing a camera that transmits images to an external recorder; the capsule does not need to be retrieved. 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 gastrointestinal 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.

More Information

The following are some English-language resources that may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

  • American Heart Association and American College of Cardiology: Guideline for the management of patients with valvular heart disease
  • American Society of Anesthesiologists Task Force: Guidelines on preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration

Drugs Mentioned In This Article

Drug Name Select Trade
lactulose CHOLAC

Copyright © 2022 Merck & Co., Inc., known as MSD outside of the US, Kenilworth, New Jersey, USA. All rights reserved. Merck Manual Disclaimer