Anatomic Considerations

Foreign bodies become impacted in the gastrointestinal tract at both normal anatomic and pathologic points of narrowing. The major factors that determine whether a foreign body will pass uneventfully or be retained are its size and configuration (e.g., rough versus smooth edges, presence or absence of projections, and width). Once pointed objects (e.g., needles or wishbones) are beyond the oropharynx, they occasionally become lodged in the pyriform processes. These areas can be seen with an endoscope but are best evaluated with a laryngoscope.

The four areas of normal anatomic narrowing in the esophagus include the upper esophageal sphincter, the thoracic inlet, the heart base, and the distal esophagus just proximal to the gastroesophageal junction. Most sharp or pointed foreign bodies become impacted in one of the latter three areas in dogs and cats. If blunt objects fail to pass through the esophagus spontaneously, the presence of an esophageal motility disorder or a pathologic area of narrowing (e.g., benign or malignant esophageal stricture) should be suspected.

Many foreign bodies that enter the stomach pass through the remainder of the gastrointestinal tract without difficulty. However, large smooth objects (e.g., rocks, balls, and lead sinkers), nonpliable materials (e.g., leather or plastic), and objects with sharp or irregular edges may be retained in the stomach because they are either too large to pass through the pylorus or their sharp edges become impacted in the antrum, pylorus, or cardia. A tubular hairball or other material may be retained because of a gastric motility disorder rather than its size or configuration.

Other points of normal anatomic narrowing in the gastrointestinal tract that occasionally become impacted with foreign material include the angles of the duodenum, ileocecal valve, and anus. Additionally, pathologic abnormalities in the intestine, such as strictures, tumors, and areas of prior surgical intervention, predispose to lodgment of foreign bodies.

Types of Foreign Bodies

Foreign bodies should be characterized as sharp or dull, pointed or blunt, and toxic or nontoxic. If the objects are visible radiographically, their length and width should be measured and the likelihood of their passing through the gastrointestinal tract without the need for endoscopic or surgical intervention should be clinically assessed. The configuration and physical makeup of an object, as well as its location, help determine whether endoscopic removal is feasible. An attempt should be made as early as possible to retrieve objects impacted in the esophagus. A variety of foreign bodies can be involved, but in our experience, bones are the most common objects found in the esophagus; most bones, fishhooks, and other objects retained in the esophagus can be successfully removed with endoscopy. Sewing needles are most commonly ingested by kittens or young cats, and frequently the alimentary tract is capable of passing these objects without incident. If possible, the clinician should determine whether any significant length of thread was attached to the ingested needle because this would increase the potential for a dangerous sequela of intestinal plication if the needle were to become impacted at the pylorus with the thread moving progressively down the intestine.

The ability of the alimentary tract to pass sharp objects such as needles is thought to be attributable to reflex mural relaxation of the intestinal musculature. Axial flow in the intestinal lumen, combined with slowing of peristalsis and reflex relaxation, tends to facilitate passage around the numerous curves of the intestinal tract. In some cases the objects actually turn around so that the sharper end trails rather than leads. Once in the colon, foreign objects often become covered by fecal material, which protects the bowel wall.

Although we have observed numerous clinical cases in which needles have successfully traversed the intestinal tract, we have also evaluated animals with peritonitis caused by foreign body perforation of the intestinal wall. In several cases, needles passed as far as the descending colon before migrating through the bowel wall and into the abdominal cavity. Because the retrieval of needles from the stomach with flexible endoscopic instrumentation is a quick and relatively easy procedure, early intervention is currently our treatment of choice rather than the more conservative but uncertain wait-and-see approach.

Patient Profiles

Although foreign body ingestion is certainly more common in young animals than middle-aged to older animals, the possibility of a foreign body–related disorder must always be considered in any animal with suggestive signs. We have seen many cases of older animals with endocrinopathies causing polyphagia or intestinal disease causing pica that present with gastrointestinal foreign body impactions. Most commonly, foreign bodies are ingested during a foray through garbage (“dietary indiscretion”) or when an animal is playing (e.g., whole or partial sections of toys chewed and eaten, balls swallowed suddenly after being caught in flight, or fishhooks and needles ingested during an inquisitive investigation). Dogs that chew rocks occasionally swallow partial or whole rocks, which may then become retained in the gastrointestinal tract. In some instances an animal ingests an object for no readily apparent reason. Included in our case files are such examples as an ingested 11-cm potato nail (see Figure 7-39, C), a rigid patch of leather ingested by a cat (see Figure 7-33), and an accumulation of ingested pine needles that caused gastric impaction in a cat (see Figure 7-38). These and many other interesting cases were successfully managed by endoscopy-guided retrieval.

Our physician counterparts encounter two dissimilar patient population profiles when dealing with foreign bodies. In most instances, ingestion of foreign bodies occurs in children, particularly between 1 and 5 years of age, who swallow objects accidentally. Most of these foreign bodies tend to be small, blunt, and nontoxic (e.g., coins or small toys) and pass without intervention. In contrast, five groups of adults have been identified as being prone to ingesting foreign bodies or to suffer from impaction of food boluses. These five groups include persons with preexisting esophageal disease (e.g., stricture, diverticulum, motility disorder, or neoplasia) or gastric disease (e.g., postgastrectomy or hiatal hernia), alcoholics, psychopaths, mentally retarded handicapped persons, and prisoners. Older adults (greater than 60 years) are much more likely to have food bolus foreign bodies. Young adults (less than 40 years) are more likely to ingest true foreign bodies (inorganic objects). It is not uncommon for prisoners and persons with psychiatric disorders to intentionally swallow a foreign body as a manipulative measure. The resulting hospital admission period with endoscopic therapy is preferable to prison or institutionalization.

Clinical Signs

Presenting symptoms resulting from a gastrointestinal foreign body vary and depend on the area of lodgment. Clinical signs related to a foreign body in the oral cavity or pharynx are usually peracute and include marked salivation (often bloody), dysphagia, pawing at the mouth and neck, avoidance of head or neck handling, pain, general anxiety, and often dysphonia or respiratory distress. Many of these clinical signs mimic foreign body impaction in the esophagus, which also includes regurgitation, odynophagia, dysphagia, forceful retching, and anorexia. Occasionally an esophageal foreign body remains undetected for a number of days. Chronic signs usually include depression, anorexia, salivation, and regurgitation. Clinical evidence of an esophageal foreign body complication, such as esophageal perforation with resultant pleuritis, mediastinitis, and pyothorax, may also be present. Other potential sequelae resulting from esophageal foreign body impaction include esophageal stricture, diverticula, and severe esophagitis.

Gastric foreign bodies are commonly associated with partial or complete outlet obstruction with accompanying characteristic symptoms. If the foreign object is freely movable, vomiting may occur only intermittently, and especially if the object is small, there may be many days when the animal displays no clinical signs whatsoever. Large foreign bodies are usually associated with frequent vomiting, and signs are usually most pronounced when the foreign body lodges in the antrum. Occasionally a tubular hairball lodges in the pyloric canal, causing complete outflow obstruction and frequent vomiting (see Figure 4-110). The presence of a gastric foreign body may also cause inappetence or complete anorexia, malaise, and nonspecific mild abdominal tenderness. The combination of pain and fever suggests perforation, which may be associated with signs of peritonitis or which may be walled off with minimal or no abdominal signs evident. Toxic foreign objects may cause other clinical signs such as seizures (e.g., seizure activity related to lead toxicity) or hemolysis (e.g., zinc from pennies minted after 1982, nails, zippers, or jewelry containing zinc). Small disk batteries used as an energy source for watches, hearing aids, and cameras contain alkali, such as potassium hydroxide, and the heavy metals mercury and cadmium. Toxicity depends on the leakage of these substances from their casings, the duration of contact with the mucosa, and the inherent toxicity of the chemicals themselves. Endoscopic or surgical removal of a toxic foreign body is mandatory if the object remains in the stomach for longer than 24 hours or if it lodges in the intestinal tract.

Sometimes the clinical signs that are exhibited seem incongruous with the type or size of foreign body present. For example, some small breed dogs become completely anorectic as a result of a small gastric foreign body such as a peach pit. The appetite predictably returns to normal as soon as the foreign body is removed. In other cases some foreign bodies that have been present for weeks to months cause minimal or no clinical signs.

Diagnostic Evaluation

The diagnosis of a retained foreign body may be readily apparent from the history. For example, an owner may have observed the garbage foray during which a bone was ingested, a section of a toy may be missing, or fishing line attached to a hook may be observed dangling from a pet’s mouth. In other cases no specific contributory historical information is available. In yet other cases the client may deny any possibility of foreign body ingestion.

Survey radiographs of the thorax and abdomen should be the first study performed because radiopaque objects can easily be localized in most cases. Cervical soft tissue radiographs are also obtained if an esophageal foreign body is suspected. Lateral films of the neck are particularly important for detecting bone fragments impacted in the cervical esophagus. Esophageal dilation anterior to a foreign body may be seen. Thoracic radiographs should be carefully evaluated for evidence of esophageal perforation, including pneumomediastinum or pleural effusion. The addition of a left lateral view to standard survey abdominal radiographs is often helpful in outlining a duodenal foreign body. More than one foreign body may be present; hence it is very important to evaluate survey radiographs carefully for evidence of additional foreign bodies that may be less obvious than an easily recognized radiopaque object.

Many commonly ingested foreign bodies (fish bones, plastic, and wood) are not radiopaque and therefore pose a significant diagnostic challenge. Some foreign bodies may be composed of both radiopaque and radiolucent materials, and as a result their size may be underestimated on survey radiographs. Stomach size is important in the assessment of radiolucent gastric foreign bodies. Gastric distension is a finding compatible with a long-standing gastric foreign body. Increased width of a localized portion of the stomach, attributable to an inability of the stomach to collapse in the involved segment, is seen with foreign bodies of lesser duration. A negative contrast gastrogram is useful in cases of a suspected radiolucent foreign body (Figure 7-1) because it may help outline a foreign body and because a negative contrast agent such as air will not mask foreign bodies as barium tends to do. A nonionic iodinated contrast agent (e.g., iohexol [Omnipaque]) can also be used in an attempt to outline a suspected esophageal or gastric foreign body. Because of the hypertonic nature of ionic contrast agents (e.g., diatrizoate [Hypaque]), a nonionic iodinated contrast agent should be used so that the chance of complications is decreased; for example, volume depletion may occur when an ionic contrast agent is given orally, and pulmonary edema may occur if the agent is aspirated.

Figure 7-1 A lateral abdominal radiograph from a 10-year-old cat with intestinal lymphoma. The animal was also positive for feline immunodeficiency virus. The cat was presented because of a gradually decreasing appetite, recent onset of intermittent vomiting, and occasional episodes of nonproductive retching. Abdominal palpation revealed a doughy mass in the region of the stomach. A, Radiograph showing a distended stomach and a soft tissue/fluid opacity. The small intestine and colon are normal. B, Gastrogram taken after 50 mL of air was injected into the stomach of the tranquilized patient through a small feeding tube. A large mass within the lumen of the stomach is consistent with a gastric trichobezoar. This simple procedure allowed rapid confirmation that a foreign body was present in the stomach. The trichobezoar was removed surgically (this mass was too wide to consider endoscopic retrieval).

(From Tams TR: Gastrointestinal symptoms. In Tams TR, editor: Handbook of small animal gastroenterology, St Louis, 2003, Elsevier.)

Foreign bodies are sometimes identified unexpectedly during routine endoscopy undertaken to evaluate patients with unexplained inappetence or vomiting. Often survey radiographs are unrevealing in these patients, and contrast studies to look for a radiolucent foreign body are not performed. Occasionally, when clients have significantly limited financial means, endoscopy is performed as a preliminary diagnostic step to avoid the expense of radiographs in patients with chronic intermittent vomiting. This is sometimes a reasonable approach, especially when patients have chronic signs and the findings of the history and physical examination are not diagnostic. Such patients are highly likely to require endoscopy with biopsy at some point, regardless of the radiographic findings. If a foreign body is found during diagnostic endoscopy, an attempt can be made to remove the object. If the foreign body cannot be removed, the patient can be taken to surgery while still under anesthesia. When a foreign body is removed, gastric and small intestinal biopsy specimens still should be obtained in animals with chronic vomiting so that concurrent problems may be identified. Sometimes a foreign body may not pass spontaneously because the patient has a motility disorder or an inflammatory disease with a secondary motility disorder. In such cases it is best to be thorough.

Overview of Treatment of Ingested Foreign Bodies

Once a foreign body has been localized, the clinician must decide whether to observe for its passage or remove the object endoscopically or surgically. Most esophageal and gastric foreign bodies are amenable to endoscopic retrieval. As a rule, any foreign object retained in the esophagus should be removed as soon as possible; if this cannot be done, the object should at least be advanced to the stomach. Esophageal perforation is uncommon but is always a risk, especially when a sharp or pointed object is involved.

In most cases an esophageal foreign body does not have to be removed as a true emergency procedure. Exceptions include foreign body impaction in the proximal esophagus that is causing respiratory distress because of tracheal compression and a wedged sharp object such as a bone that is causing significant patient distress. These situations may be evidenced by groaning, copious salivation, or forceful gagging. If rapid intervention is not required, the patient should be stabilized as needed with intravenous fluids, antibiotics, and pain medications (e.g., hydromorphone or morphine plus a transdermal fentanyl patch if ongoing pain is anticipated), and a thorough radiographic assessment should be completed. Ideally endoscopy should be undertaken within 4 to 12 hours of presentation. Endoscopy is indicated as the initial procedure of choice for all esophageal foreign bodies. If endoscopic equipment is not available, the patient should be referred to an appropriate facility.

Sharp or pointed objects, such as pieces of plastic, needles, and safety pins, should be removed from the stomach endoscopically. As discussed previously, needles frequently pass through the gastrointestinal tract uneventfully, but early removal is recommended because of the increased potential for complications with such objects and the high success rate of endoscopic retrieval. Rounded or blunt gastric foreign bodies often pass spontaneously; therefore, if significant clinical signs such as frequent vomiting are not present, such patients may be managed conservatively with close observation and radiographic surveillance for 3 to 7 days. If signs of obstruction develop and the foreign body has passed out of the stomach, surgical intervention is indicated. Performing esophagoscopy and gastroscopy immediately before surgery is still recommended so that the esophagus and stomach can be quickly assessed for any injury resulting from either foreign body trauma or esophagitis secondary to reflux and vomiting or any signs of concurrent disease. If only surgery is done, these types of problems will go undetected. Although some animals can retain gastric foreign bodies for long periods of time with minimal untoward effects, it is always best to remove objects retained for a prolonged period (greater than 2 to 3 weeks) so that chronic mucosal damage is avoided.

Some foreign bodies can be successfully retrieved from the upper small intestine endoscopically, but if an object becomes impacted to any degree, it is usually quite difficult to grip it firmly enough with foreign body graspers to move it. An enterotomy is then required.

Endoscopic foreign body removal has numerous advantages over other means of treatment. The procedure is highly successful, minimally invasive, and not appreciably time-consuming. In our experience, endoscopic foreign body retrieval generally requires 5 to 15 minutes once anesthesia is induced. Especially troublesome objects may require up to an hour, but endoscopy is still less expensive and less invasive than surgery. Patients are often discharged within 4 hours to 2 days of the procedure. Endoscopy allows for rapid intervention when sharp objects or valuable prized possessions such as jewelry or coins are ingested. Rather than rely on observation and radiographic surveillance in such clinical situations, the clinician can use endoscopic equipment to quickly retrieve the object in question. The main limiting factor with endoscopy is the necessity for general anesthesia.

Foreign bodies that are not likely to be removed endoscopically include corncobs, large rocks (bigger than the rocks shown in Figure 7-39, A), large hard rubber balls (e.g., Superball), large wide hairballs in cats, Gorilla Glue concretions, and sometimes heavy objects such as lead sinkers. Problems with retrieval of foreign objects are related to their size in relation to the width of the grasping range of pronged foreign body retrieval instruments, the diameter of basket and snare instruments, the weight or surface texture of the foreign body, and the grasping strength and quality of the foreign body retrieval instruments being used. Smooth objects are sometimes difficult to grasp firmly enough for retrieval through the narrow areas of the lower and upper esophageal sphincters. Recently, larger basket and rigid grasping instruments have been developed, and previously irretrievable objects such as golf balls can now be more routinely removed (see the “Instrumentation” section).

Although the majority of gastrointestinal foreign bodies will be successfully removed endoscopically, those that are not can be managed surgically. There have been conflicting opinions about the indications for and success of transthoracic esophagotomy for the removal of esophageal foreign bodies. Indications for surgical removal of an esophageal foreign body include an inability to push the object into the stomach because of firmness of impaction, difficulty in grasping the object (which prevents movement), or severity of esophageal damage (e.g., perforation). Historical studies of esophagotomy have reported a discouraging combined survival rate of 70% with a range of 43% to 100% and significant complications associated with incisional dehiscence. A more recent study reported a specific surgical protocol in 14 dogs that had a success rate of 93% for foreign body removal from the thoracic esophagus without increased risk of complications.

Client Education

Although endoscopic retrieval of foreign bodies is highly successful and done routinely in small animal clinical practice, there are complications and outcomes that owners must be made aware of before the procedure begins.

Because most foreign body retrieval procedures are done within minutes to hours of an animal ingesting the offending object, the animal has not been properly fasted for anesthesia. This involves a slightly higher risk of reflux, regurgitation, and possible aspiration of gastrointestinal contents during anesthesia and after the procedure. The resulting possible complications include reflux esophagitis, esophageal stricture formation, and aspiration pneumonia. If the foreign body does not require emergency removal, waiting a few hours can significantly reduce this risk by allowing ingesta to leave the stomach. If more than one hour has passed, radiographs should be taken to judge the position of the foreign body before beginning the procedure.

If a foreign body is impacted within the esophagus, owners need to be educated about potential life-threatening risks. Although extremely rare, sharp objects within the esophagus have the potential to perforate the aorta at the level of the aortic arch or pierce through the esophagus into the chest cavity. These complications would require extensive emergency care and could prove fatal. In most cases, one of three outcomes can generally be expected with esophageal foreign bodies: (1) the foreign body may be removed uneventfully, (2) the foreign body may be advanced into the stomach and may require a gastrotomy to remove, or (3) a thoracotomy and esophagotomy may be required to remove the foreign body. Obtain advance permission for any of these procedures so the anesthesia time is not prolonged while waiting for owner consent. Regardless of the technique utilized to remove the esophageal foreign body, the owner should also be informed that a temporary gastrotomy feeding tube may be necessary depending on the extent of damage done to the esophagus.

Instrumentation

A variety of instruments are available for foreign body retrieval. A laryngoscope and forceps (e.g., Kelly clamp, sponge forceps) should be immediately available for removing oral and pharyngeal foreign bodies and any object that is difficult to pull through the upper esophageal sphincter with standard prong-type endoscopic grasping instruments. Until the 1970s the rigid endoscope was always used for retrieving esophageal foreign bodies. Today, however, the flexible endoscope is the instrument of choice because visualization and maneuverability are greatly enhanced. In some cases it might be best to use a flexible endoscope in conjunction with a rigid scope. Areas such as the stomach and duodenum, which are inaccessible to a rigid endoscope, can easily be reached with a flexible endoscope as long as it has sufficient length. Nonetheless, it is still advantageous to have several rigid scopes of different lengths and diameters available for selected esophageal bone foreign body cases and for possible use as an overtube for the flexible endoscope.

A variety of foreign body forceps are available for use with flexible endoscopes. The diameter of the working channel of the endoscope limits to some degree the type and size of grasping instruments that can be used. Larger, sturdier instruments made by some manufacturers require a 2.8-mm or larger working channel. Pediatric endoscopes that are less than 8 mm in diameter usually have a 2-mm channel, although smaller diameter endoscopes with a 2.8-mm diameter instrument channel will soon be available. In our experience, however, a majority of gastric and esophageal foreign bodies can be successfully retrieved with instrumentation that can be used through a 2-mm channel.

Two-, three-, and four-pronged grasping instruments are most commonly used for foreign body retrieval. A sturdy two-pronged instrument (Figure 7-2) is adequate for grasping many foreign objects and can be used with a pediatric endoscope that has a narrow working channel. Sturdy three-pronged (tripod) graspers usually require a 2.8-mm channel. Sheathed four-pronged graspers can be purchased for use in small working channels, but these instruments do not tend to be as durable. Alligator-jaw forceps (Figure 7-3) are particularly useful for grasping smooth flat objects. Rat-tooth forceps (Figure 7-4) have excellent gripping power and are especially useful for retrieving heavy cloth objects such as large socks or towels or large trichobezoars.

Figure 7-2 Two-pronged grasping forceps. The width between the grasping teeth (when fully separated) is approximately 1.4 cm. This is a versatile instrument because of its grasping teeth and long arms, as well as the adequate space between the grasping ends when the arms are fully extended.

(Courtesy of Olympus America, Inc., Center Valley, Pa.)

Figure 7-3 Alligator-jaw grasping forceps.

(Courtesy of Olympus America, Inc., Center Valley, Pa.)

Figure 7-4 Sharp (rat-tooth) grasping forceps with an opening width of 4.7 mm. This instrument requires a 2.8-mm instrument channel. (The two-pronged instrument shown in Figure 7-2 can be passed through a 2-mm instrument channel.) The grasping strength of the rat-tooth forceps is excellent, and the instrument is particularly suited for retrieving heavy cloth (e.g., socks, towels) and other pliable or relatively thin objects.

(Courtesy of Olympus America, Inc., Center Valley, Pa.)

Polypectomy snares are among the most versatile instruments for removing foreign bodies (Figure 7-5). The snare loop can be extended around an object to provide a much stronger grasp than can sometimes be achieved by the single-end grasp applied by a pronged instrument. Round objects with a smooth surface (e.g., balls) are much more easily grasped with a snare than with a pronged instrument, which typically slips off the object as the prongs are closed around it (Figure 7-6). Basket retrievers (Figures 7-7 and 7-8) are less commonly required but may be a little more effective in extracting smooth, rounded objects. The large basket shown in Figure 7-8 has improved capabilities for retrieving larger objects. It was designed by Dr. Vicente Torrent, a veterinarian from Spain with extensive case experience in endoscopic removal of bones and other large objects, including many cases of golf ball ingestion. Net retrievers (Figure 7-9), such as the Roth Net, feature a flexible, durable pouch that can be helpful in the removal of round, blunt, or otherwise hard-to-grasp foreign bodies. We have found the net retriever to be useful for coin removal. When a stack of coins is present, they can often be scooped out simultaneously with a net instead of individually. Standard endoscopic biopsy forceps generally are not useful for removing foreign bodies other than thin, light objects. In fact, it is strongly advised that endoscopic biopsy instruments not be used for foreign body retrieval because such use may damage the forceps or cause the edges to become dull and thus less effective for procuring adequate-size tissue samples.

Figure 7-5 Oval (left) and crescent (right) grasping snares.

(Courtesy of Olympus America, Inc., Center Valley, Pa.)

Figure 7-6 Snare technique used to remove a hard, smooth-surfaced ball from the stomach. A prong-type instrument would be inadequate for grasping this object.

Figure 7-7 Basket-type grasping forceps. This instrument can be passed through a 2-mm instrument channel.

(Courtesy of Olympus America, Inc., Center Valley, Pa.)

Figure 7-8 Large six-wire foreign body basket. A, Full instrument including tubing and basket extended and opened. This large instrument requires a 2.8-mm instrument channel. B, Close-up with basket opened to full extent. When opened completely, the basket is 14 cm long and 10 cm wide (spacing between the wires), which makes this a very versatile instrument for retrieving large objects.

(Courtesy of Karl Storz GmbH & Co. KG, Tuttlingen, Germany.)

Figure 7-9 Roth Net retriever. This instrument is useful for scooping up stacks of coins.

(Courtesy of US Endoscopy, Mentor, Ohio.)

Experienced endoscopists have personal preferences regarding the types of grasping instruments they like to use in certain situations. Our advice to veterinarians who are purchasing foreign body retrieval instrumentation is to obtain high-quality sturdy instruments that are built to last. Avoid, if possible, disposable endoscopic foreign body retrieval equipment as it tends to be less sturdy and of lower quality. Lower quality instruments may cost less, but they tend to be somewhat less effective and less durable, and significant frustration often results from their use. A minimum of two types of instruments is advised: a two-prong grasper with long arms (see Figure 7-2) and a snare loop instrument (see Figure 7-5). Once experience has been gained, an endoscopist can successfully retrieve a majority of gastric foreign bodies with one of these two instruments. Our next preference would be a rat-tooth instrument (see Figure 7-4) if the endoscope working channel can accommodate an instrument of this size. Finally, net and basket instruments complete the basic endoscopic instrument armamentarium.

Another invaluable instrument in esophageal foreign body removal is a rigid grasping forceps designed for laparoscopic use (e.g., Duval forceps, Figure 7-10). While visualizing the foreign body using a flexible endoscope, the endoscopist advances the forceps alongside the endoscope and grasps, firmly holds, and removes the offending object. These forceps have significantly more holding power than any other piece of equipment used through the scope and have been particularly helpful in removing large bones. As they are such firm graspers, care must be taken to apply only gentle traction during removal to avoid esophageal perforation. Even larger graspers are now available for retrieving objects such as golf balls from the stomach (Figure 7-11).

Figure 7-10 A, Duval atraumatic laparoscopic grasping forceps (bottom) and Claw grasping forceps (top). These instruments provide exceptional gripping strength and are particularly useful for esophageal bone foreign body retrieval. Instrument specifications: Duval: 5-mm diameter and 36-cm long, double-action jaws with length of 4 cm, opening 4 cm at full extent; Claw: 10-mm diameter and 43-cm long, single-action jaws with length of 3 cm, opening 3 cm at full extent. B, Close-up of jaws of the Duval grasper. C, Close-up of jaws of the Claw grasper.

(Courtesy of Karl Storz GmbH and Company KG, Tuttlingen, Germany.)

Figure 7-11 Rigid instrument set for removal of esophageal and gastric foreign bodies (Richard Wolf GmbH, Knittlingen, Germany). The set includes a long telescope, two types of optical foreign body grasping forceps (one designed for small and the other for large objects), and a scope sheath for examination with the telescope. For object retrieval under direct visualization, the telescope is inserted directly into the optical grasping forceps. Air can be insufflated through the Luer fitting on the sheath and the grasping forceps. Instrument specifications: The telescope is 98 cm long and 8.5 mm in diameter. The sheath is 13.5 mm in diameter. The optical grasping forceps are 97.4 cm long (for large objects) and 95.5 cm long (for small objects) and 15.8 mm in diameter. A, Telescope (top), sheath (middle), and optical grasping forceps (bottom). B, Telescope inserted and locked into optical grasping forceps. C, Large grasping forceps with jaws closed. D, The large grasping forceps has oversized jaws capable of grasping large objects such as the golf ball shown in this photo. E, Smaller grasping forceps with jaws open. These instruments were designed by two Spanish veterinarians (Dr. Vicente Torrent and Dr. Elena Mora) with extensive experience in endoscopic retrieval of large foreign bodies from dogs (e.g., bones and golf balls).

An overtube is another extremely useful ancillary instrument that protects the esophageal mucosa when sharp or pointed foreign bodies must be removed. This tube fits over the endoscope, and sharp objects are drawn into its lumen before the endoscope and tube apparatus are withdrawn from the patient. Overtubes may be purchased commercially, or they can be made from tubing. The inner diameter of an overtube should be approximately 2 mm larger than the outside diameter of the endoscope. The end should be beveled smooth to facilitate passage and to prevent mucosal trauma from sharp edges. An endotracheal tube or rigid endoscope can also be employed as an overtube. For use in the stomach, an overtube should be 50 to 60 cm long; a shorter tube usually suffices in the esophagus.

The tube is first passed over the endoscope to the level of the control handle (Figure 7-12). The endoscope is then inserted in the usual manner, and the overtube is advanced as needed. The inner walls of the overtube should be well lubricated to allow easy passage of the endoscope through it. When a foreign body is being removed, the grasping forceps should withdraw the foreign body into the overtube, thereby protecting the mucosal surface (Figure 7-13). An overtube can be useful even if a sharp object cannot be completely drawn into its lumen. Because it has a wider diameter than the endoscope, the overtube serves to maintain better dilation at the lower and upper esophageal sphincters, thus making it less difficult to pull an object through these orifices.

Figure 7-12 Overtube in position on a flexible endoscope.

Figure 7-13 Example of the usefulness of an overtube in the removal of a sharp foreign body. A, An opened safety pin is grasped firmly at the blunt end with a forceps instrument before withdrawal into an overtube. B, The endoscope with safety pin is being pulled into the overtube. C, The safety pin has been totally withdrawn into the overtube. The use of this technique keeps the sharp point of the safety pin from coming into contact with mucosa. The overtube and endoscope can be safely withdrawn at the same time.

Use of an overtube has several minor disadvantages. With an overtube in place, it may be more difficult to read the measure markings on the endoscope; thus the total length of insertion may not be readily apparent. A more troublesome problem is that the overtube may interfere with torquing of the endoscope, which makes thorough scanning in the stomach somewhat more difficult. Therefore, when dealing with a gastric foreign body, the endoscopist should usually complete the diagnostic portion of the procedure before or after using the overtube.

In our experience it has rarely been necessary to use an overtube in retrieving foreign bodies from animals. The most significant advantage provided by an overtube has been in facilitating passage of wide foreign bodies through the narrow areas of the lower and upper esophageal sphincters.

Endoscopic Removal of Esophageal Foreign Bodies

Safe extraction of an esophageal foreign body requires an adequate preliminary evaluation and the selection of proper equipment, including the appropriate grasping forceps or snare. An overtube, laryngoscope, and curved grasping forceps should also be readily available in case their use becomes necessary. Patient evaluation includes a thorough physical examination that would identify problems directly related to the foreign body, such as dyspnea, gagging, bloody saliva, fever, and dehydration, and problems that may complicate the use of general anesthesia, such as preexisting cardiac disease. After the physical examination is performed, analgesia must be provided to enhance patient comfort. If there is concern about analgesics causing vomiting (e.g., pure opioid agonists), a problem that should be controlled if at all possible in an animal with an esophageal foreign body, maropitant (Cerenia) or dolasetron (Anzemet) are highly effective antiemetic drugs that can be administered to control this potential problem. Preanesthetic laboratory work should be performed to help identify other preexisting conditions such as renal disease or complications from the foreign body. Leukocytosis with a left shift may be present in some cases of long-standing bone impaction causing secondary infection of the esophageal mucosa or in cases of esophageal perforation with resulting pleuritis or mediastinitis. Cervical and thoracic radiographs are carefully reviewed to determine foreign body conformation and location and to look for evidence of esophageal perforation. If pleural fluid is present, the chest should be tapped to obtain a sample for cytology, Gram stain, and culture and sensitivity studies. Pyothorax is best managed with the placement of a chest tube for drainage and lavage. Once the patient is stabilized, a thoracotomy is done as soon as possible, either alone or in conjunction with endoscopy, to remove the foreign body and to evaluate and repair the esophageal wall. In general, it is rare for bone foreign bodies that have been lodged in the esophagus for several days to weeks to cause complete esophageal perforation.

As with any type of esophagogastroduodenoscopy procedure, the patient is maintained under general anesthesia in a left lateral recumbent position. In this position the esophagus lies above the aorta. A properly inflated endotracheal tube is especially important in preventing tracheal compression as a large foreign body is pulled retrograde through the esophagus and in preventing aspiration of any object that might be inadvertently dropped in the pharynx during retrieval. After complete oral examination, the endoscope should be passed under direct visual guidance through the pharynx and upper esophageal sphincter to avoid striking any foreign body material that may be present in the proximal esophagus and that subsequently may damage the mucosa. As the endoscope is advanced, the esophageal mucosa should be carefully evaluated for any foreign body–related damage. For enhanced visualization, air should be insufflated to distend the esophageal walls, but the patient’s respiratory status must be carefully monitored while this is done. Air may be forced around an impacted foreign body and into the stomach, which can lead to significant gastric distension with resultant respiratory and cardiovascular compromise. Cats and small dogs are most at risk. The distension should be relieved as quickly as possible. In most cases this can be done by periodically passing the endoscope or narrow diameter tubing around the foreign body and into the stomach so that the air can be suctioned. Air insufflation to a perforated esophagus can also result in acute respiratory signs. The anesthetist is advised to monitor both respiratory character and degree of gastric distension during the procedure.

Successful extraction of a foreign body requires adequate visualization, a firm grasp of the object, and removal with minimal force so that further damage is avoided. The endoscope tip should not be used as a ramming rod to dislodge or advance an object because significant damage could be incurred to the endoscope. Once freed, most objects can be pulled back to the tip of the endoscope. The endoscope and foreign body are then gently removed simultaneously. Undue force should never be exerted; gentle manipulation is the rule. If possible, pointed objects such as bones and needles should be withdrawn with the pointed edge trailing. If a sharp end is positioned proximally, the grasping prongs can sometimes be used to cover it (e.g., toothpick or needle), thus protecting the esophageal mucosa, or the object can be advanced to the stomach and repositioned so that the sharp end trails. This latter technique works well when irregular pieces of a material such as plastic are involved. Alternatively, objects with sharp or irregular edges can be removed with the aid of an overtube to prevent mucosal damage. After an esophageal foreign body is removed, the scope should be reintroduced; the entire esophagus should be inspected for damage, and the stomach should be examined for the presence of any foreign material. Some degree of mucosal laceration usually occurs at the site of foreign body impaction in the esophagus. The extent of damage should be carefully evaluated, and appropriate medication should be instituted after the procedure.

The most commonly encountered esophageal foreign bodies in dogs are bones and fishhooks. Techniques for their removal are discussed in detail in the following sections. Rigid sections of plastic may also become impacted, and these objects behave similarly to bones. Esophageal foreign bodies are encountered much less commonly in cats, but the management principles are identical.

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