The advantages and disadvantages of endoscopy

The Advantages and Disadvantages of Endoscopy Lisa E. Moore, DVM, DACVIM-SAIM

Endoscopy is generally a very safe and effective tool in the diagnosis and therapy of various gastrointestinal (GI) disorders, and must be used in conjunction with other diagnostic modalities. Endoscopy should not be a substitute for a complete work-up. There are many advantages of endoscopy, including minimal morbidity and mortality, and the sensitivity of this modality in the diagnosis of mucosal disorders of the GI tract. However, complications may occur, and there are limitations to endoscopy. This article will provide an overview of when to choose GI endoscopy and when other procedures might provide more information. © 2003 Elsevier Inc. All rights reserved.

astrointestinal (GI) endoscopy is the visual examination of the lumina of various parts of the intestinal tract, namely the esophagus, stomach, duodenum, ileum, and colon (Fig 1). Endoscopy is generally a very safe and effective tool in the diagnosis and therapy of various GI disorders. But, it must be used in conjunction with other diagnostic modalities, especially radiographic procedures, and is considered a complementary tool. Endoscopy should not be a substitute for a complete history, physical examination, and appropriate laboratory procedures. The indications for endoscopy are varied and include signs of GI disease that cannot be attributed to disease in other body systems.1 Anorexia that is not accompanied by other clinical signs may also be an indication for upper endoscopy. There are also therapeutic indications for endoscopy, namely the retrieval of foreign objects. There are few contraindications for endoscopy, but there may be instances in which it is not the optimal diagnostic or therapeutic tool.2

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The Advantages of Endoscopy One of the major advantages of endoscopy is that it is minimally invasive. Endoscopic procedures do require anesthesia and some minimal preparation but can often be performed as soon as it is deemed necessary. Animals undergoing esophagogastroduodenoscopy should be fasted for at least 12 hours, and preferably for 24 hours, because delayed gastric emptying often occurs with GI disease.3 Animals undergoing colonoscopy From the Veterinary Medical Teaching Hospital, College of Veterinary Medicine, Kansas State University, Manhattan, KS. Address reprint requests to Lisa E. Moore, DVM, DACVIM-SAIM, Assistant Professor, Veterinary Medical Teaching Hospital, College of Veterinary Medicine, Kansas State University, 106A Mosier Hall, Manhattan, KS 66506. © 2003 Elsevier Inc. All rights reserved. 1096-2867/03/1804-0007$30.00/0 doi:10.1016/S1906-2867(03)00000-0

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should be fasted for 36 to 48 hours (some investigators prefer 72 hours).4 These animals should receive enemas up to 12 hours before the procedure.4 Warm water only should be used because soap and other ingredients may irritate the colon. The best way to prepare animals for colonoscopy is to administer 2 to 3 doses of an osmotic solution (Go-Lytely, Braintree Laboratories, Braintree, MA) orally the day before the procedure.5 The morbidity and mortality rates of endoscopy are very low.3 Once it has been deemed the appropriate procedure, there are few reasons not to proceed. The only real contraindication is an animal that is unfit for anesthesia. Animals that have other medical problems, whether related or unrelated to the primary GI disease, should be stabilized as much as possible before anesthesia. Animals that are anemic from GI bleeding should receive a transfusion before anesthesia. Complications that may be encountered during or after endoscopy are covered in a subsequent section. The endoscopic removal of a GI foreign body is the best example of the therapeutic potential for endoscopy (Figs 2 and 3). Most objects lodged in the esophagus, stomach, proximal duodenum, and colon can be removed via endoscopy.1-3,6-8 Exceptions may include smooth objects that do not have any defects on their surface or bones that are deeply embedded into the wall of the GI tract. Balloon dilation and bougienage procedures for esophageal and colorectal strictures can also be performed (Figs 4 and 5).2,6,9 Caution should be used with these techniques in the colon (surgery may be a better option).4 Percutaneous endoscopic gastrostomy tubes can be placed for nutritional support.2,10 Endoscopy is very sensitive in the diagnosis of mucosal diseases of the esophagus, stomach, proximal duodenum, ileum, and colon.2-4,6 In addition, endoscopy allows for collection of cytologic, histopathologic, microbiologic, and parasitologic specimens.2-4,11,12 Endoscopy is a great tool to visualize and obtain biopsy and/or microbiologic specimens from the intestinal mucosa. The biopsy forceps can obtain a sample several millimeters deep into the mucosa. Lesions, such as neoplasia, superficial gastroenteritis, and Helicobacter spp colonization can be detected via endoscopic biopsy. Ulcerations and erosions are easily visualized (Fig 6). Gastric mucosal hypertrophy, as well as gastric and duodenal polyps can also be seen. Cytology brushes can be used to obtain cytologic specimens, which may aid in the diagnosis of various GI diseases.12 Endoscopy surpasses radiographic contrast studies in the diagnosis of gastric and duodenal mucosal, and luminal diseases (Fig 7).13 Most endoscopic equipment will allow for photographic and/or video documentation of diseases.14 Lesions that can be visualized can also be photographed or taped, either with a videoendoscope or an attachment for a fiberoptic endoscope. Lesions seen at endoscopy can be documented in this fashion

Clinical Techniques in Small Animal Practice, Vol 18, No 4 (November), 2003: pp 250-253

Fig 1. Endoscopic view of a normal canine ileocecocolic valve area illustrating the cecum and ileocolic valve (“mushroom” appearance).

for the medical record, which is invaluable if the animal is ever scoped again, and for teaching purposes and client education.

Disadvantages Endoscopy cannot detect functional disease of the GI tract or estimate luminal diameter as well as other techniques.2,6 Motility disorders of the intestine, such as esophageal dysmotility or irritable bowel syndrome, cannot be detected via endoscopy.

Fig 2. Endoscopic view of an esophageal bone foreign body in a dog lodged near the heart base. THE ADVANTAGES AND DISADVANTAGES OF ENDOSCOPY

Fig 3. Same dog as in Figure 2. Endoscopic view of the esophagus after the bone foreign body has been removed. Hemorrhage is noted where the bone damaged the esophageal mucosa.

Again, only mucosal and intraluminal disease can be detected. Contrast radiographic procedures can provide a better estimation of luminal diameter and motility. The endoscope can only be inserted as far as the descending duodenum in large dogs, and the very proximal jejunum in small dogs and cats. Therefore, the majority of the jejunum

Fig 4. Endoscopic view of an esophageal stricture in a dog secondary to reflux of gastric contents during a previous anesthesia.

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Fig 5. Same dog as in Fig 4. Endoscopic view of the esophageal stricture following balloon dilation. Note the hemorrhage associated with tearing of the strictured mucosa.

cannot be visualized, and samples cannot be taken for histopathology.3 This may limit the ability to diagnose the disease or the severity of the disease process in some animals. Although most diseases of the GI tract will be diffuse, in dogs and cats it has been shown that the severity of inflammation can vary between intestinal sites in an animal with inflammatory bowel disease.15,16 Consequently, biopsies of the stomach and duodenum may not be representative of the disease process, and full

Fig 6. Endoscopic view of the distal esophagus in a cat with protracted vomiting showing esophagitis.

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Fig 7. Endoscopic view of a gastric adenocarcinoma in a dog. Note the raised, irregular edges of the tumor with a central depressed area that is ulcerated.

thickness biopsies taken from multiple areas are likely to provide more information. Endoscopy cannot detect diseases that primarily involve the submucosal, muscularis, or serosal layers of the intestine.2 Biopsy specimen size is limited by the cup size of the instrument used, generally measuring 2 to 3 mm. Therefore, the biopsy sample may be only 2 to 3-mm deep into the intestinal mucosa. Several samples may be taken in the same spot to obtain deeper samples, but care must be exercised to avoid perforation. Diseases that extend into the submucosa also may not be detected via endoscopy. Gastrointestinal lymphosarcoma (GI-LSA) is the best example in which endoscopic biopsy may not tell the whole story. This disease appears to originate in the submucosa.17 While most GI-LSA lesions involve diffuse infiltrates of lymphocytes in the submucosa and lamina propria, occasionally, transmural infiltration through the serosa occurs.18 Also, lymphoplasmacytic inflammation may be present along with the neoplastic infiltration. Even with full-thickness intestinal biopsy samples, it can, at times, be difficult to differentiate LSA from inflammatory bowel disease.18 Therefore, a diagnosis of GI-LSA may be very difficult with endoscopic biopsies. Endoscopy is not an appropriate procedure if bowel perforation is suspected.2 Insufflation of air into the bowel performed during endoscopy may increase contamination of the peritoneal cavity through an already existent perforation. If extraluminal gas or a paracentesis reveals septic exudate, abdominal surgery would be the most appropriate next step. Endoscopy is not encouraged if the animal is inadequately prepared. As mentioned previously, an animal must be adequately prepared before endoscopy, or visualization of the mucosa will be difficult-to-impossible.2,3 Food particles can get lodged in the scope if suctioning is attempted. The procedure should be postponed until the animal is adequately prepared because it is neither worth the time nor expense to attempt endoscopy in an animal with food or barium in the stomach or feces in the colon. LISA E. MOORE

As mentioned previously, although endoscopy is generally very safe, complications are possible and do occur.2,3 GI perforation can occur when attempting to remove an esophageal or duodenal foreign body, especially one that is lodged in the mucosa.8 Perforation of the stomach, duodenum, and colon are highly unlikely but can occur if excessive force is placed on the scope to round corners or from poor biopsy technique.2,19 Severe disease, such as a deep gastric ulcer, can increase the risk of perforation, especially if deep biopsies are taken. Laceration of major blood vessels or major organs adjacent to the GI tract can also occur.3 This is highly unlikely to happen but can occur with excessive pressure or force placed on the endoscope. Decreased venous return and/or hypoxia may occur if the stomach is overinflated with air.2,19 A large, distended stomach can cause a decrease in venous return to the heart via the vena cava (similar to what happens in gastric dilation/volvulus). A large, distended abdomen may also decrease the animal’s ability to expand the chest during inspiration, and hypoxia can result. This complication is easy to prevent by careful monitoring of the patient during the procedure. Gastric dilation/volvulus on recovery has occurred rarely in animals that have undergone endoscopy.2 The removal of as much air as possible before completion of the procedure will prevent this complication from occurring. Bradycardia may occur due to vasovagal stimulation during the procedure.2,3,19 This most often occurs when pressure is applied to enter the scope into the duodenum, especially in small dogs. Stimulation of the vasovagal reflex may be a result of overdistention of the GI tract or traction on the mesentery.2 Premedication with an anticholinergic, such as glycopyrrolate, may help prevent this complication as will careful monitoring of heart rate during anesthesia. Excessive mucosal hemorrhage may also occur as a complication of endoscopy.2 Diseased intestinal mucosa may be more likely to bleed excessively compared with normal mucosa. Excessive bleeding rarely occurs to the point at which intervention is necessary. Exceptions may include ulcerations and neoplasia. Bacteremia after endoscopy has been documented in humans20 and is likely to occur in animals, although no reports have been published in veterinary medicine. In humans, although bacteremia occurs in a portion of patients, there are few in whom actual infections occur.

Summary Endoscopy is a very safe, effective tool for the diagnosis of various mucosal diseases in dogs and cats. Although special equipment and a certain expertise are required, it is becoming a more widely available modality. Proper preparation of the patient and careful technique will minimize potential complications.

THE ADVANTAGES AND DISADVANTAGES OF ENDOSCOPY

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