Diagnostic and Therapeutic Endoscopy of the Stomach and Small Bowel

Endoscopy is the gold standard for providing visual access to the endoluminal space of the gastrointestinal (GI) tract for diagnostic and therapeutic purposes. As a diagnostic tool, it allows for direct visualization of the mucosal surface and permits the identification of abnormalities including mucosal changes, polyps, strictures, and external compression. As a therapeutic tool, the included instrument channel allows passage for instruments that can sample mucosa for pathologic examination, treat bleeding, dilate strictures, and access other organ pathologies through the wall of the GI tract. Upper GI endoscopy allows for examination of the esophagus, stomach, and proximal duodenum down to the ligament of Treitz. The small bowel between the ligament of Treitz and the ileocecal valve is more difficult to access although techniques such as video capsule endoscopy and balloon endoscopy have expanded the roles of endoscopic evaluation and therapy. Endoscopy is a growing domain and a majority of GI pathology either involves the mucosa directly or can be identified indirectly from within the lumen of the GI tract.

Indications and Contraindications

General indications for endoscopy include persistent upper abdominal symptoms despite appropriate medical therapy or have associated worrisome symptoms such as vomiting, weight loss, anorexia, dysphagia, and odynophagia. Other indications include chronic or iron-deficiency anemia without a source on colonoscopy, evaluation of suspicious radiographic abnormalities, or surveillance for premalignant lesions or conditions such as familial adenomatous polyposis. Indications for therapy include tissue sampling and excision, treatment of acute upper GI bleeding (UGIB), foreign body retrieval, dilation or stenting of strictures or leaks, and placement of feeding tubes.

Relative contraindications for endoscopy under conscious sedation include inability to tolerate the procedure or sedation, inadequate patient cooperation, and suspicion of perforated viscus. It is possible to perform endoscopy in these cases under general anesthesia, although the risks and benefits must be weighed carefully and that the potential result of the endoscopy should change future management. Endoscopy in patients with a suspicion of perforation is best done with carbon dioxide insufflation and the ability to quickly decompress pneumoperitoneum surgically if required. Surgical anastomoses are considered safe to be evaluated endoscopically. Patients with recent myocardial infarction, stroke, or pneumonia should be assessed independently for risk of worsening their existing comorbidity. Coagulopathy or inhibition of platelet aggregation is a relative contraindication for therapeutic procedures.

Equipment

Endoscopy Tower

An endoscopy tower is used to concentrate and organize the equipment needed to perform endoscopy within a compact and portable unit. It generally includes a digital video processor, which allows connection of the endoscope electronics to provide signal-to-video and post-processing capabilities. It should also allow capture and saving of still pictures and video for documentation purposes. A light source is also important, interfacing with the light-guide cables of the scope to provide illumination that travels to the tip of the endoscope. Finally, a video monitor provides a display capability that allows the endoscopist and assistant(s) to directly visualize the magnified picture produced by the camera at the tip of the scope.

Most common optional equipment includes a foot pedal–activated auxiliary water pump, which allows the production of a water jet for lavage through the auxiliary water channel. A radiofrequency generator or other source of energy is usually also bundled, allowing the delivery of monopolar cautery and bipolar/thermal energy. Finally, an accessory insufflator can be used to allow luminal distention with carbon dioxide.

Endoscope

The modern endoscope includes an objective lens and a charge-coupled device (CCD) camera at the tip. A light-guide system enables transmission of illumination from the light source. Cables allow for angulation and deflection of the instrument tip. The endoscope also supplies channels for insufflation and optionally an auxiliary water channel. Importantly, there is also an instrument channel through which therapeutic modalities can be delivered ( Fig. 57.1 ). The size of the instrument channel can vary from scope to scope, with diagnostic scopes having smaller channels and therapeutic scopes with larger or even double channels. Mini-scopes also exist to facilitate passage through tight strictures. Moreover, the objective and instrument channels can be placed at the tip of the instrument (end viewing) or to the side of the instrument (side viewing), which are adapted to visualization of specific regions of the GI tract.

Preparation

Prior to endoscopy, an assessment of general medical condition, medication allergies, the patient's ability to tolerate the procedure, and prior reactions to sedation should be undertaken. Prior airway issues should be explored. In case of therapeutic intervention, an up-to-date coagulation panel and platelet count should be checked to ensure it is within safe ranges. If fluoroscopy is considered, pregnancy testing should be considered for women of childbearing age. Informed consent should be taken detailing the risks and benefits of the procedure.

For routine upper GI endoscopy, the last oral intake of solids should be 6 hours and clear liquids 2 hours prior to intervention. This helps prevent regurgitation and aspiration and improves endoscopic visualization. In cases of known gastroparesis or obstruction, a longer fasting period or the prior insertion of a nasogastric tube to empty the stomach may be appropriate. In GI bleeding, lavage may be performed through a nasogastric tube both as a diagnostic tool and to help clear clots and blood, thereby improving visualization.

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