Flexible endoscopy is minimally invasive surgery, and as with all surgical procedures, things can go wrong. The problem is that most of the time it is an internist doing the endoscopy, and he/she is not really aware that endoscopic mishaps can be just as life threatening as those that occur with the more classic, “maxi-invasive” surgery. Typically, not having possible complications in the forefront of his/her thought, it is easy for the endoscopist not to notice the warning signs that problems are brewing. This often means that when complications do occur, the endoscopist is not prepared to deal with them in an expeditious fashion. Consequently, when things do go wrong, the patient can suffer and/or die.

The main complications that can occur directly as a result of any flexible endoscopy of the gastrointestinal tract are: a) perforation/rupture resulting in septic inflammation and/or accumulation of air in a body cavity, and b) laceration causing severe haemorrhage. There are other complications that are somewhat unique to specific procedures.

Oesophagoscopy

Oesophagoscopy is typically done in patients that are also having a gastroduodenoscopy. However, there are some indications for just doing oesophagoscopy. Suspicion of or rechecking known oesophagitis, benign strictures, oesophageal foreign body, tumour, and/or hiatal hernia are all potential reasons to do oesophagoscopy without gastroduodenoscopy. Occasionally oesophagoscopy is appropriate to look for Spirocerca lupi infestation and other rare causes of oesophageal disease in pets that are regurgitating. However, oesophagoscopy is seldom useful for evaluating oesophageal motility problems caused by muscular weakness. Oesophageal mucosa is seldom biopsied in dogs unless a mass or an obvious infiltrative lesion is seen. It might be useful to biopsy cats, but that is an area we are now learning about.

The equipment for oesophagoscopy is the same as for gastroduodenoscopy; however, it is generally not as critical to have a small diameter endoscope if one is not interested in entering the pylorus and duodenum. Flexible scopes are typically very superior to rigid scopes when seeking to evaluate the oesophageal mucosa. On the other hand, rigid scopes are much better when trying to remove foreign objects. By using a rigid endoscope, one can use rigid retrieval forceps which allow a firmer hold on objects. However, rigid colonoscopes are not especially long, and it is rare that they can be used to remove foreign objects in dogs that are more than 25 to 30 pounds. Unfortunately, flexible scopes typically must be used in these large dogs.

Preparation is less important as the oesophagus generally does not retain food unless there is weakness or an obstruction, and neither situation is likely to be substantially improved by waiting.

While no special preparation is needed for oesophagoscopy, it is clearly best to avoid barium contrast oesophagrams because they can make the procedure much more difficult.

Anaesthesia is the same as for gastroduodenoscopy. Inhalant anaesthesia is best as it allows one to maintain a patent airway, which is especially important when removing large foreign objects that have the potential to put pressure on the trachea. In addition, it is important to carefully monitor the patient when using a rigid scope because a malpositioned scope can put too much pressure on the heart, great vessels, and airways. The patient is usually best placed in lateral recumbency. If you are using a rigid scope, it is very important to keep the oesophagus as straight as possible. After the patient is adequately anaesthetized, you should pass the scope through a protective mouth gag to the larynx. You must always look through the scope as it is advanced. Air insufflated into the oesophagus can pass into and fill the stomach; therefore, you must be cognizant of the amount of air insufflated. You should keep the center of the oesophageal lumen in the center of the scope’s viewing field. Insufflate sufficient air to distend the oesophagus as the tip of the scope is advanced through the cricopharyngeal sphincter and down the oesophagus.

The normal oesophageal mucosa is pale and smooth except just caudal to the cricopharyngeal sphincter; at this point it may be slightly roughened. Submucosal blood vessels can be seen, especially when one is looking at the lower oesophageal sphincter. The distal feline oesophageal mucosa has many small folds. These folds correspond to the site of the herringbone pattern seen on barium oesophagrams. Be sure that you do not over insufflate as you pass the scope through the oesophagus because an excessively distended stomach can put so much pressure on the diaphragm that it becomes difficult for the patient to breathe. In addition to that, over inflation can increase the distance that the tip of the endoscope must travel along the greater curvature as it approaches the pylorus. Thus, excessive distention of the stomach may “make” the scope too short to enter the pylorus. The lower oesophageal sphincter may be open but often appears as a slit. Do not push the scope blindly through this sphincter if it is closed. Instead, you should aim the tip toward the slit and carefully advance it.

Visualization Problems

Sometimes there is so much foam in the oesophagus, stomach, or intestines that visualization is significantly impaired. Instilling a solution of 1-part dimethicone or simethicone plus 9-parts water through the biopsy port into the foam will often cause the foam to disappear or at least become thin enough that it can easily be aspirated.

Oesophagitis

Oesophagitis is usually obvious to the endoscopist. One can typically see erythematous, bleeding, and/or ulcerated areas; however, exudate can make it difficult to perceive the ulcerations.

Strictures

Cicatrix (i.e., scarring) may occur after an episode of severe oesophagitis from any cause (including foreign objects). It is particularly easy to miss this problem on a barium swallow if only liquid barium is used. If radiographs using liquid barium are nonrevealing, repeat the study using barium mixed with food, which is more likely to stop at a partial obstruction. Endoscopy is very good at finding these lesions; however, you must keep in mind the size of the patient as you evaluate the oesophageal lumen. A partial stricture will be very obvious in a 5 kg dog or cat but may not be apparent in a 40 kg animal. Balloon-dilatation or bouginage is usually effective; it is also more likely to be successful than surgery and resection of the affected area. In general, surgical resection should be a last-ditch resort and only used if oesophageal ballooning or bouginage has failed despite repeated dilatations. However, you must use proper oesophageal balloons because Foley catheters and endotracheal tubes with inflatable cuffs will often not allow you to dilate a dense or mature stricture. More difficult cases (i.e., those with extensive strictures or with concurrent severe oesophagitis) may benefit from a couple of techniques.

Endoscopic administration of intralesional steroids may help minimize reformation of the stricture. Typically, we put 1–2 ml of Vetalog at the site of the stricture either before or after ballooning. Another technique is to make 3–4 equidistant cuts into the stricture using an electrocautery device (i.e., either a snare or a knife) prior to ballooning. This helps the stricture to “break” open at multiple spots with the idea that there will be 3 or 4 smaller, less deep lacerations at the stricture site instead of one major, deep laceration which is more likely to restricture. However, you should not attempt to use cautery through an endoscope unless you have some training lest you cause too much trauma to the tissues or destroy your endoscopic equipment.

Another technique is to “paint” the site where the stricture was broken down with Mitomycin C (not Mythromycin C, there is a difference). A 5 mg bottle is reconstituted and soaked up into a gauze sponge. Then this sponge is endoscopically placed on the site where the stricture was broken up for 5 minutes. Then it is flushed off with 60 mL of water.

Finally, for particularly difficult cases, stents may be placed in the oesophagus. These must be sutured in place. The major point to remember is that if an animal starts to have problems days to weeks after anaesthesia, consider strongly the possibility that an oesophageal stricture has developed secondary to oesophagitis. If you are treating an oesophageal stricture, remember that you may need to do 1–15 dilatations. If oesophagitis is diagnosed, you need to treat it aggressively in order to help prevent the stricture from recurring quickly.

Foreign Objects

Foreign objects usually consist of bones but may be rawhide treats, food, dental chew toys, toys, balls, rocks, wood, etc. They usually lodge at the thoracic inlet, base of the heart, or lower oesophageal sphincter. A history of a patient that begins to regurgitate (as opposed to vomit) acutely is very suggestive of acquired oesophageal obstruction due to a foreign object. These patients may continue to drink water, but they typically refuse solid food because the food bolus cannot pass by a partial oesophageal obstruction and causes pain whenever it tries to. A casual, careless history that fails to raise the suspicion of regurgitation will typically lead the clinician to suspect an acute gastritis. However, the realization that the patient is regurgitating (as opposed to vomiting) should be a “red flag”. Too often, a pet which has ingested a foreign object is treated conservatively while we wait and see if the supposed gastritis spontaneously resolves. This is problematic because foreign bodies can erode and perforate the oesophagus much quicker than they would stomach or intestines.

Plain radiographs should be performed first. Bones are a common cause of obstruction, and plain films that are made with proper technique and then carefully evaluated are diagnostic in most cases. Remember that poultry bones are not as radiodense as the patient’s bones, which means that excellent radiographic technique is required to see them. Foreign bodies in the oesophagus can perfectly mimic pulmonary or mediastinal masses; you often cannot tell the difference with plain radiographs. If poor contrast in the region of the oesophagus, pleural effusion, or pneumothorax are seen, one must seriously consider oesophageal perforation and mediastinitis. If plain films are not diagnostic, then contrast films can be performed. Barium provides better contrast, but iodide is safer if there is an unsuspected perforation. Oesophageal perforation may occur at variable times after ingestion of a foreign object. Even a blunt object, if tightly lodged in the oesophagus, can cause ischaemia and perforation in 2–3 days. The prognosis for animals with oesophageal perforation and severe mediastinitis is guarded to poor, depending upon their condition at the time of diagnosis.

Endoscopy is almost always the preferred method of removing foreign objects, but fluoroscopic and surgical techniques can be effective if the operator is well trained. Rigid endoscopes allow much more control of the foreign object and are preferred to flexible scopes for removal of these foreign objects. It is especially useful to be able to pull the object into a rigid endoscope and then withdraw it and the scope as a unit, thus protecting the oesophagus. The main disadvantage of rigid endoscopes is that they are often not long enough in larger dogs. Finesse is required; brute force can easily lacerate/perforate the oesophagus. If a large object or a bone cannot be easily dislodged, do not force it lest you perforate a previously intact oesophagus; instead, you can use rigid equipment to “chew” it up and hopefully dislodge it. If that fails, passing a large Foley catheter behind the foreign object and inflating the balloon often helps; it distends the oesophagus (thus freeing the foreign object) and then is used to pull the object out. If you cannot pull a foreign object out of the oesophagus, you can try to push it into the stomach. However, do not push bones or other foreign objects into the stomach unless you are sure that it is smooth on the aborad side and will not further damage the mucosa. Finally, be careful if you insufflate the oesophagus lest you rupture a weakened area in the mucosa and/or cause a fatal tension pneumothorax.

Fish hooks terrify many clinicians, but they can often be successfully removed endoscopically. Fish hooks have usually penetrated the mucosa (and sometimes the muscular tunics); you will often have to use rigid equipment to carefully force the tip of the hook back out of the mucosa. A small hole is left, but there are very seldom any complications. After removing the foreign object, retake plain chest radiographs to be sure that a pneumothorax (which would indicate a perforation) is not present. Antibiotics are indicated if there is substantial oesophageal mucosal ulceration (and especially if you remove a fish hook which had been used with various baits that can harbor anaerobic bacteria). Depending upon the amount of damage, corticosteroids may be used to try to prevent cicatrix formation; however, it is not clear that they are effective. Rarely there may be severe haemorrhage.

Gastroduodenoscopy

The patient should be prepared by holding it off food for at least 24–36 hours as animals with gastrointestinal pathology may not empty their stomachs readily. The patient must be completely anaesthetized (i.e., one bite on your scope may cost you $4,000–6,000 to repair). Avoid narcotic pre-anaesthetics such as fentanyl as they may make it harder to pass the instrument through the pylorus. The procedure will tend to stimulate the patient, so have the anaesthesia watched carefully. Also remember that as the stomach is distended with air, it will become harder for the patient to take deep breaths, and one may have to bag the patient to ensure that an adequate plane of anaesthesia is maintained.

The basic principles to remember are:

1.  Only go where you can see. Do not advance the instrument blindly.

2.  If you cannot see well, put more air in and distend the lumen.

3.  If you cannot see well, pull the scope back and try to get a panoramic view.

4.  If you cannot see well, try aiming the scope into the center of the lumen (i.e., centralize).

I place the patient in left lateral recumbency and insert a mouth gag. One observes through the scope as it is advanced into the mouth and through the cricopharyngeal sphincter. Air is insufflated and one then advances the scope into the oesophageal lumen, observing the mucosa. When the lower oesophageal sphincter is seen, the tip of the scope is advanced through it, and the stomach is insufflated with air (an exception to this is the very large patient in which case it is better to advance the scope into the duodenum first, so that dilation of the stomach does not result in being unable to enter the duodenum.). Once the stomach is dilated with gas, one examines the greater curvature which is front of the scope. The scope is then advanced along the greater curvature and the tip is retroflexed so that the antrum, the incisor angularis, and the body of the stomach (with the lower oesophageal sphincter through which the endoscope is entering) can be seen. Now, the body of the stomach is examined.

Next, the scope is advanced into the antrum until the pylorus is seen. If it is hard to make the tip of the instrument go into the antrum, placing the patient in dorsal recumbency often helps the operator to manipulate the instrument into this area. With the patient in left lateral recumbency, the pylorus is usually off to the left. If the pylorus appears polypoid, it may be particularly hard to pass through. Metoclopramide has not proven useful in passing the instrument into the pylorus, but ketamine seems to cause some degree of relaxation in some cases. The opening of the pylorus should be kept in the center of the viewing field as the scope is advanced. If necessary, push the tip against the pylorus, being sure to keep the opening in the centre of your field of view. Remember that the duodenum often turns to the right, just after one passes through the pylorus. If it seems difficult to get through the pylorus, one may try to sweep the tip to the right while pushing it against the opening, in an effort to slip into the duodenum.

Do not extensively reposition the patient during the procedure lest you cause gastric volvulus. If a gastric volvulus occurs because of your manipulations while the patient has a distended stomach, wait and see. These usually spontaneously resolve.

Hiatal Hernias

Hiatal hernias may be more common than suspected. Shar Peis seem to have a relatively high incidence of hiatal hernias. They can be difficult to diagnose unless you know how to look for them. Sometimes seen on plain radiographs and simple barium contrast radiographs, the more occult cases sometimes need more aggressive diagnostics. Sometimes one must manually put pressure on the abdomen during film exposure to try to push the stomach through the hernia and into the chest so that it can be diagnosed radiographically. Endoscopic diagnosis is not always straightforward. You may need to put the endoscope into the stomach and retroflex it in order to see the abnormality. Even when found, the big question is whether the hiatal hernia is causing a problem or is an “innocent bystander.” In particular, if you have an older dog or cat (i.e., >1–2 years old) that just started having clinical signs, you should strongly consider that the hiatal hernia is a fortuitous finding that is not responsible for the clinical signs.

Foreign Bodies

Gastric foreign objects require a variety of special retrieval instruments to reliably remove. The most useful devices include a coin-retrieval device (also called a W-tooth retrieval device, which is effective for many other objects besides coins), a rat’s tooth or shark’s tooth forceps (which is especially useful for firmly grabbing cloth), and a 4-wire basket. The basket should be made of very flexible wire in order to facilitate its being passed over and around an object; however, this quality makes it easier to bend the wire and ruin the basket. They must open up to a relatively wide diameter (e.g., 40 mm) and be made of very pliable wire. If their maximal diameter is less or if the wire is stiff, it becomes very difficult to get the foreign object into the basket and snare it. By the same token, the best baskets are easily damaged and ruined because they are made of very pliable wire. Other retrieval devices include wire snares, 3-wire grabbers, magnetic tipped probes, and forceps with non-skid rubber. However, these latter instruments are seldom required. Three wire grabbers (i.e., tripod type retrievers) are very popular with salesmen, but not so popular with busy endoscopists. Unless they are very well made, they usually do not do a very good job of holding onto large objects, heavy objects, and those which generate a lot of resistance when being removed (e.g., panty hose).

Each foreign object to be removed must be considered individually lest an ill-planned endoscopic removal be more damaging to the patient than the foreign object. Poor technique may damage or perforate the alimentary tract (or the scope). It is also possible to “grab” a foreign object and then find that it cannot be removed or released, thus necessitating surgery to retrieve the endoscope. This could be extremely embarrassing.

There are numerous techniques for foreign body removal; only a few basic principles will be discussed. The animal is always radiographed immediately before anesthetizing it to remove the object. Some foreign objects that have been present for weeks will pass out of the animal or out of reach of the scope just before the endoscopic procedure is to be performed. A retrieval forceps that will allow a firm grasp on the object is selected. The object may have to be manipulated until the best possible purchase upon it is possible. Once an object is snared, it should not be pulled out against undue resistance. Resistance is expected at the lower oesophageal sphincter (gastric cardia), the base of the heart, the thoracic inlet, and the cricopharyngeal area.

Snare the gastric foreign object, then, draw the object up next to the tip of the endoscope. Flex the tip so that it goes through the cardia without pressing against one side more than the other. If the object is still difficult to pull into the oesophagus, pass the flexible endoscope through a larger diameter rigid endoscope or rubber tube (i.e., an “over-tube”). “Grab” the foreign object and remove it from the stomach by carefully passing the over-tube down the flexible scope until the over-tube enters the stomach. Then, carefully draw the flexible scope, with the foreign object as close to the tip as possible, as far into the over-tube as possible. Remove both the scope and the foreign object as one unit. This technique is also useful for pulling objects through the cricopharyngeal sphincter as well as removing objects with sharp edges (e.g., glass, razor blade, safety pin, etc).

Whenever a foreign object has been removed, the mucosa should be re-evaluated to look for erosion/ulceration and the presence of other foreign objects or lesions. If a foreign object which could penetrate the alimentary tract has been removed, one should radiograph the appropriate body cavity to look for evidence of perforation (i.e., pneumothorax or pneumoperitoneum).

Linear Foreign Objects Lodged at the Pylorus

When removing linear foreign objects which are trailing off into the duodenum, one should attempt to pass the endoscope through the pylorus so that one can grab the distal end (or at least near the distal end) of the object. The distal end is then pulled into the stomach, meaning that little or none of the object remains in the intestine. If there is still a little bit of the foreign object in the intestine, it can usually be removed simply by pulling it into the stomach. If the foreign object is relatively thick (e.g., cloth, cotton), as opposed to thin (e.g., twine, string, narrow strips of cloth), one can try to pull it into the stomach simply by grasping it near the pylorus and pulling. However, this approach risks rupturing the duodenum, especially if the foreign object has been present for more than 2–4 days. Therefore, this approach should only be tried with caution.

Biopsies

While not too exciting to many people doing endoscopy, taking superb tissue samples is the difference between the mediocre, so-so endoscopist and the superb diagnostician. Many clinicians doing endoscopy of the small intestines are taking inferior biopsies and consequently are missing important diagnoses. This is very common. Unfortunately, most people are not too interested in learning to take good biopsies, possibly because some pathologists call everything “mild to moderate, lymphoplasmacytic something or the other,” and hence the client can be handed a diagnosis (regardless of whether it is right or wrong). We will not discuss interpretation of biopsies at this time. The clinician’s job is to provide the pathologist with the absolute best possible tissue sample. That is what we will spend some time discussing now.

Biopsy is typically the major purpose of intestinal endoscopy. If you cannot take a biopsy that is adequate for diagnosis, then you should probably not be doing endoscopy. This takes a lot of practice and patience, plus direct contact with the pathologist so that you know if you are taking good biopsies or not. There are various types of biopsy forceps for use with flexible endoscopes.

I prefer ones that have jaws that are:

1.  Ellipsoid

2.  Fenestrated

3.  Have serrated jaws

The ellipsoid jaws allow one to obtain a larger mucosal sample than the round jaws, simply because the ellipsoid jaw forceps can encompass more volume. The fenestration in the jaws minimizes compression artifact when larger samples are obtained. I don’t know that the serrated jaws make much difference, but they look better and I feel better about using them. I distinctly dislike biopsy forceps with a blade or needle in the center. Forceps with such a blade or needle are designed to allow you to drive the needle into the area you want and then exert more force or pressure against the mucosa without having it slip off the lesion. However, I find that these forceps typically result in a distinctly smaller mucosal sample. Sometimes the sample is literally cut in two by the blade.

Flexible endoscopic biopsy of the alimentary tract has several advantages. It is:

1.  Quick (i.e., usually <20 minutes to obtain gastric and duodenal samples)

2.  Safe

3.  Of minimal stress to very ill animals

4.  Allows you to see and biopsy mucosal lesions which typically cannot be seen from the serosal surface

5.  Typically diagnostic, if done correctly

However, flexible endoscopy is starting to get a bad reputation because of all the inaccurate diagnoses that have occurred in animals that were sampled using this technique. This centres on the comment that flexible endoscopy is typically diagnostic if done correctly. There is a lot of endoscopy that is incorrectly done, especially in regards to obtaining tissue samples. The problem is that while the smaller diameter endoscopes are very easy to use (i.e., it is easy to put them into small orifices and pass them through small pylori), these are the scopes with the smaller biopsy channels. It is particularly easy to obtain mediocre (or outright inadequate) tissue samples with biopsy instruments designed for scopes with a biopsy channel that is 2.2 mm in diameter. Scopes with a biopsy channel of 2.8 mm typically allow excellent tissue samples to be consistently obtained; however, these scopes are often large in diameter (e.g., >9.0 mm), making them harder to use in cats and dogs <3 kg. Therefore, the clinician must make a decision based upon how often he/she will be performing endoscopy, because that usually determines how accomplished they will become and what they can afford. One should use fenestrated, ellipsoidal forceps with a serrated edge. Then, you keep taking sample after sample until you obtain good samples that encompass the full thickness of the mucosa down to and preferentially including the muscularis submucosa. If the sample fragments easily, then it is primarily villus tips and is inadequate. You may submit it, but do not count it. At least 6–8 good tissue samples should be obtained in hopes that at least 2 or 3 will be well oriented. Immediately after obtaining the sample, it is carefully removed from the biopsy forceps with a 25-gauge needle and gently spread out on a tissue cassette sponge such that the luminal side (i.e., the side with the villi) is oriented upwards and the sample is no longer folded. The samples are allowed to adhere to the sponge, but are not allowed to dry out. The sponge with the tissue samples is placed in formalin promptly. The most important points to take home are that substantial attention to tissue handling is critical in order to give the pathologist optimal tissue samples. A lot of endoscopic procedures have been a complete waste of time and money because the tissue samples were either of poor quality or were mishandled. Always take multiple biopsies of an area because some lesions are very spotty and will be found in less than half of the samples from that area. The value of the endoscopic procedure is totally dependent upon how exacting and demanding you are when taking biopsies.

As alluded to, there are some disadvantages to flexible endoscopy of the alimentary tract:

1.  It requires expensive equipment

2.  It is easy to take inadequate samples

3.  Some lesions are out of reach of the endoscope

4.  Some lesions are so dense that you cannot obtain a diagnostic biopsy of them with this equipment.

Scirrhous carcinomas and pythiosis are the two major examples of such lesions.

Colonic and Ileal Biopsies

It is becoming apparent that biopsying both the small and large intestines is useful in many patients (especially cats), even though the clinical signs suggest that only the small or large intestine is involved. It is desirable to use a flexible scope when obtaining colonic samples (in addition to the rigid scope) so that the ileo-colic valve area can be inspected and one may obtain ileal mucosal samples. We can usually enter the ileum of dogs weighing >5–7 kg, but it is rare that the tip of the scope can be advanced into the ileum of cats. However, even in small dogs and cats, the biopsy forceps can usually be passed through the ileocolic valve and ileal tissue obtained by performing blind biopsies of the mucosa.

Flexible colono-ileoscopy is indicated in any animal with signs of large bowel disease (e.g., haematochaezia, mucoid stool, diarrhoea without weight loss), but especially when rigid colonoscopy and biopsy are nondiagnostic. It is also useful for obtaining ileal biopsies in animals with signs of small intestinal disease (e.g., diarrhoea, weight loss, vomiting) and animals with signs of ileal intussusception (e.g., protein-losing enteropathy in young dogs; persistent vomiting/diarrhoea after an acute enteritis such as parvovirus; elongated mass in abdomen; sudden onset of scant, bloody stools in a vomiting animal with abdominal pain; sudden deterioration in an animal with prior abdominal surgery/disease), or caecal intussusception (e.g., haematochezia despite relatively normal stools, bloody diarrhoea not diagnosed with rigid colonoscopy). Flexible gastroduodenoscopes are preferred; however, larger diameter human colonoscopes can be used. If ileoscopy is desired, it is best to use smaller diameter (i.e., <9.8 mm) equipment.

Perform a digital rectal examination before the endoscope is inserted into the rectum, to be sure there is not a lesion close to the anus that may be missed or perforated by the rigid scope. Lubricate the tip of the colonoscope and insert it approximately 2–8 cm into the rectum.

With flexible colonoscopy, bends and twists are even more common as the ileo-caeco-colic valve area is approached. In the dog, the ileo-colic valve may vary in appearance, but it usually has a “mushroom” shape and is relatively easy to identify, if the area is clean. However, it is easy to slide past a normal ileo-caeco-colic valve area and into the caecum without realizing that the caecum has been entered. If this happens, the endoscopist will find that the “colon” is making turns that the scope cannot go past and the caecum may be perforated. This area may be less well prepared than the rest of the colon.

The caecal lumen should be examined for whipworms and growths and then biopsied. After that, one should attempt to enter the ileum or blindly pass a biopsy instrument into the ileum. The scope is passed into the ileum in much the same manner as for the pylorus. However, the ileo-colic valve is rarely open and one will usually have to gently push the tip of the scope into the ileum. There may be paradoxical movement (i.e., the tip of the scope does not move even though the insertion tube is being advanced into the colon because the middle of the insertion tube is pushing laterally on the colonic wall and causing it to move to the side) when attempting to push the tip of the scope into the ileum.

The cat caecum is a short, blind pouch whereas in the dog it is a longer, coiled chamber that is easy to enter by mistake. However, it is easier to enter the ileum of the dog than it is the ileum of the cat. The main reason for this is that the feline colon (especially the transverse and ascending) is relatively short and it is difficult to position the tip of the endoscope so that you have a good view of the ileocolic valve or can approach it with the tip of the endoscope in the manner that you desire. Most of the time, all we can do is blindly pass a biopsy instrument into the ileum, and even that can be very difficult.

Rigid colonoscopy is very useful to examine and biopsy the descending colon. Rigid endoscopy is perhaps the easiest and the most cost-effective endoscopy of the alimentary tract that one can learn. Rigid endoscopes are less expensive and yet typically allow the operator to obtain all the information that is needed in the majority of cases. This technique will be diagnostic in probably greater than 80% of cases which need colonoscopy. The rigid scopes used for rigid colonoscopy can also be used for oesophagoscopy, and they are in fact my favorite tools for removing oesophageal foreign objects. Rigid colonoscopy is usually performed using rigid human sigmoidoscopes. In general, one should use the scope with the largest diameter and longest length that a given patient can accept; this maximizes the ability to examine the mucosa. In all but toy dogs, one can usually use endoscopes with diameters of 19 to 27 mm. Cats often require endoscopes with diameters of 11 to 15 mm.

Rigid proctoscopes are very useful for examining lesions at or near the anus. They absolutely do not replace colonoscopes, but they do have their place. They come in various lengths (e.g., approximately 70 to 130 mm) and diameters (e.g., approximately 8–25 mm). Some have areas of the distal wall cut out and are referred to as operating proctoscopes. This cut-out area allows the clinician to position the scope such that a mass protrudes into the lumen of the scope, making it easier to biopsy or remove it. Proctoscopes are usually used on top of a battery handle, much like an otoscope. Some proctoscopes use transformers that plug into electrical outlets.

The alligator biopsy instrument used with rigid endoscopes needs to be of high quality in order to obtain optimal mucosal samples. One must be able to insert it into the rigid endoscope and have the tip extend beyond the opening (preferably several cm). The author prefers biopsy instruments that have tips that cut and shear the mucosa as opposed to clam-shell biopsy cups that pinch off a piece of mucosa. The latter rapidly become dull and often tear off mucosa, producing substantial artifact. It is helpful to have the tip of the biopsy tip at a 30° or 45° angle, instead of being a straight continuation of the cannula. This alligator biopsy instrument should only be used for sampling soft mucosa; use on foreign objects or other hard material can produce nicks and dulling which will result in inferior biopsy samples.

Electrocautery Procedures

If you are using any of the various endoscopic instruments that have electrocautery capability, you would do very well to spend more time reading the instructions than playing with the instrument, at least the first time you do the procedure. It is important to understand that if the tip of the cautery instrument is too close to the tip of the endoscope, applying an electric current may result in electricity being directed up the endoscope and into the video processor and light source, thereby blowing them out and leaving you with a huge repair bill.

As far as the patient is concerned, there are several potential pitfalls, especially when using electrocautery loops to resect lesions such as polyps. First, do not apply so much current that the burn you create in the mucosa causes worse signs than the original lesion caused. Start with a relatively low voltage (I typically blend cutting and coagulation and use a setting of about 15–20 on each) and work your way up. Second, when you are tightening the snare around the base of the polyp or mass, do not use excessive force or you may end up cutting through the polyp without the benefit of adequate coagulation (and cause substantial haemorrhage as a result). Never blindly grab anything with the snare; you need to be able to see well enough to have confidence that you did not include anything in the snare that you do not want to cut.