Endoscopic Evaluation of the Upper Digestive Tract
Because of the increase in comfort, safety, and accuracy of endoscopic examination, it has replaced barium studies as the procedure of choice for evaluating the esophagus, stomach, and small intestine and colon. Upper endoscopy is very accurate and is considered the “gold standard” diagnostic test for most luminal upper digestive tract disorders. Barium contrast fluoroscopic x-ray studies are highly operator dependent and limited in quality in the best of hands. For example, barium contrast studies will be able to diagnose fewer than 65% of the causes of upper gastrointestinal bleeding (and therefore are contraindicated in such situations). Endoscopy can be performed in an ambulatory setting and anywhere in the hospital, permits the taking of pathologic specimens, and may be used to perform therapeutic interventions. Nearly all patients prefer to be sedated or even to be given monitored airway control heavy sedation, but such comfort measures are not essential for all patients and are not provided in all countries. The ordering physician must know when to use barium contrast studies performed by a radiologist and when to use endoscopy.
It is important for the clinician ordering endoscopic procedures to understand their special uses and quality metrics and the advantages and disadvantages of barium studies compared with endoscopic studies. Although it is technically the more invasive diagnostic test, endoscopy is perceived as being more comfortable because it is performed with sedation, and, therefore, it is much preferred by patients. Endoscopy is also preferred because it is much more accurate and permits the taking of specimens for cytologic, microbiologic, or pathologic assessment. It is also used to perform a wide variety of therapeutic procedures. If appropriate, this invaluable tool can be brought to the bedside of the sickest patients in the hospital’s intensive care unit for both diagnostic and therapeutic interventions. In contrast, all radiologic studies require the transportation of the patient to the specialized x-ray equipment located in the radiology department of the hospital, except for the simplest of plain x-rays and ultrasound studies. This section will briefly describe the process of upper endoscopic procedures and the use of three upper gastrointestinal endoscopic procedures, endoscopy, endoscopic retrograde cholangiopancreatography (ERCP), and endoscopic ultrasonography (EUS). The ordering physician must appreciate when to use these studies and the potential risks and quality metrics to look for in the results.
Ensuring the patient’s safety is of the highest priority in endoscopy. One must ask if the procedure is clearly indicated, whether this is the safest approach to getting the diagnosis or treatment, and whether this is the optimal time in the course of the patient’s illness to perform the procedure. Cardiac, pulmonary, and coagulation studies are not usually indicated, but they may be needed in select patients who have unusual risks. The endoscopist must be aware of all underlying medical conditions, all prescribed and over the-counter medications taken, and any concerns about the coagulation status. If possible, anticoagulants should be held if intervention is anticipated, but this is not always possible or prudent. Knowing the status of the patient’s platelet count and coagulation tests is imperative if one has any reason to suspect they are abnormal, especially if intervention is planned. If the patient has an active cardiac or pulmonary condition, including obstructive sleep apnea, the patient must be assessed, if necessary by a cardiac or pulmonary specialist. Because morbidly obese patients are particularly at risk, office endoscopy is not recommended for them, and they may require preprocedure assessment.
Once the procedure has been scheduled, the patient must be aware of her or his responsibilities. One of the most common severe complications from upper endoscopic procedures is aspiration pneumonia. Except in select cases, the procedure is performed without protection of the airway by intubation. Thus the patient must have taken no food by mouth for at least 6 hours and no clear liquids for at least 2 hours. Of course, these standard times for fasting should be longer in patients at high risk for aspiration, including those with achalasia and gastric emptying disorders. Special instructions should be given to patients regarding their blood pressure and diabetic medications. In patients with active bleeding, the blood pressure and pulse should be made as normal as possible by crystalloid fluid and, if necessary, blood resuscitation. Before starting the procedure, time should be taken to ensure that all providers and nurses are aware of the patient’s risk factors, including allergies, risks of the procedure to be performed, and risks of any intended interventions.
Endoscopy is generally a very safe test and can be performed in nearly all patients with ease and no anticipated ill effects within 5 to 15 minutes (or longer if interventions are performed). It can provide highly accurate imaging of the entire upper digestive system to the distal duodenum or, if enteroscopy is performed, well into the jejunum or ileum. Histologic, microscopic, or cytologic specimens increase the diagnostic accuracy with negligible risk. Interventions are commonly performed with endoscopy, including dilations of the esophagus or duodenum, the placement of stents to treat resistant strictures or cancers of the esophagus or duodenum, and the placement of feeding tubes. The key to quality is adequate analysis of all parts of these organs with photo documentation and the taking of a sufficient number of biopsies in accord with published guidelines. It has been shown that the errors of upper endoscopy occur when sufficient time is not taken to examine parts of structures that are challenging to see clearly or to achieve a thorough evaluation. This includes examining all of the esophagus; documenting the site of the squamocolumnar junction; examining in detail the fundus in a retroflex view; examining the angularis, pylorus, and all parts of the bulb of the duodenum; and reaching at least the third part of the duodenum. The guidelines for diagnosing specific upper gastrointestinal disorders should be understood by the ordering physician (see Sections 2 to 4). For example, one should obtain at least six biopsy specimens through- out the esophagus to rule out eosinophilic esophagitis, nine specimens of gastric ulcers to rule out malignancy, and six specimens of the duodenum, including two in the bulb region, to rule out celiac disease.
ERCP will be discussed at length in the chapter on biliary disorders. Only very highly skilled endoscopists perform this procedure, usually after a fourth year of training or many years of experience. It can often provide therapeutic intervention that avoids major surgery, including bile duct stone extraction and ductal stenting. Diagnostic ERCP has rarely been indicated since EUS and MRCP have become available, both of which can examine the bile duct and ampulla in detail with negligible risk. In years past, it was common to hear that the duct could not be cannulated, but in expert hands, this is now a rare occurrence. Because of its potential duration, this is the one upper endoscopic examination that may require preemptive planning for intubation and general anesthesia.
EUS is performed by endoscopists who are trained at length on its uses. The procedure is performed with an endoscope that has been modified by the placement of one of several transducer types at the tip of the scope. It has become the procedure of choice to examine nodes adjacent to abdominal organs and the esophagus; the distal common bile duct; submucosal lesions and pancreatic lesions; and fluid collections. It is highly accurate for lesions that may be only millimeters in diameter because the transducer is placed directly on the lesion.
It also permits the collection of cytologic specimens by using fine-needle aspirates of the lesions and/or biopsies. In the setting of cysts or abscesses, EUS can be used diagnostically to collect intralesional fluid for culture, cytologic, or biochemical assessment or therapeutically to drain the lesion. It can also be used to guide an interventional procedure such as pancreatic cyst drainage by creating an endoscopic cyst gastrostomy.