Gastrointestinal
Endoscopy in Dogs
Introduction
Endoscopy is a Greek word comprising of “Endo” for Inner and “Skopein” to view or observe with a purpose and Fiberoptic
endoscopy is a noninvasive technique for evaluating the lumen and mucosa of the
gastrointestinal tract of dogs. It is a fundamental method for investigation of
the digestive tract, and is important in the diagnosis and prognosis of a
variety of gastrointestinal disorders.
It is indicated mainly if history and physical
examination of a patient reveals abnormalities in the area of the gastrointestinal
tract. In addition to this further investigations like plan and contrast
radiography, ultrasonography and functional tests may permit tentative
diagnosis. Until recently clinician had been limited in their ability to
diagnose GI diseases morphologically because of the need to carry out an
exploratory laparotomy in order to obtain biopsy samples and has been largely
replaced by endoscopy.
Endoscope’s Structure and Equipment for
Endoscopy
According
to their structure endoscopes are divided into two groups: rigid endoscopes which are hermetically mounted in a metal tube and
have an optical lens system, and flexible
fiberscope which have a flexible working part and transmit the imagine via
the light fiber optics. Mobility of the distal end of endoscope and its
controlled movement in one or two dimensions provides an examination and a
biopsy in the necessary place.
Rigid
tubes endoscopes (otoscopes, esophagoscopes, rectoscopes, and laparoscopes) are
simpler devices that look like metallic tubes through which the cavities are
examined by the naked eye. Such devices are used for shallow entering. Flexible
endoscopes with fiber optics (fiber endoscopes) differ from the rigid by its
flexible working part. It allows the endoscope to go down the bent anatomical
channels deep located cavities. To transmit the images the fiber light path
with orderly structure of certain fibers is used in flexible endoscopes that
helps to prevent image distortion.
Endoscopes Disinfection
and Sterilization
Before the examination it is necessary to check the
quality of the image, water and air supply, the integrity of the outer hull
system. After conducting the examination the biopsy channel of the endoscope
should be washed with a Luke-warm water (30-35° C; 2 liters)), followed by
washing in running water with neutral detergent. After washing the endoscope
should be carefully wiped with a soft cloth. The surface of the flexible tube
is wiped with 70% alcohol.
The valves of the biopsy channel
should be taken off and wiped with a sponge and washed by alcohol. After
washing the biopsy channel of the endoscope is dried in the air from the
insufflator. Biopsy forceps and loops are thoroughly washed in warm water with
soap, wiped with alcohol and dried. The final disinfection of fiber endoscopes
and instruments is made by plunging them in glutaraldehyde solution, or by gas
sterilization with ethylene oxide or formaldehyde. Autoclaving can be used only
for tools and parts of the device that cannot be damaged under the influence of
heat and pressure.
Preparation of
Animal for the Examination
Preparation starts with withholding of food for 36 hours and water for 4
hours prior to examination. A plain Radiograph should be taken prior to
examination that may rule out any foreign body obstruction. Endotracheal intubation
should be done by tying the endotracheal tube to
the mandible instead of maxilla that aids in the passage of the endoscope into
the oesophagus. The patient is
placed in the left lateral recumbence.
Anesthesia
for gastrointestinal endoscopic examination
Animal must be properly
restrained during endoscopic examination by giving general anesthesia using
mainly intravenous anesthetic products and also preanesthetic like atropine before
30-40 minutes of the examination must be give that reduces the secretion of
salivary and other digestive glands and decreases muscle tonicity of
gastrointestinal tract. Diazepam is a widely used tranquilizer (2-10 mg intramuscularly).
Endoscopic
Procedure
Endoscopy of esophagus, stomach, and duodenum is
performed after withholding food for about 36 hours. The endoscope is
introduced with the dog in left lateral recumbence. During the examination the
presence and character of contents, and the appearance of the mucosa, are
noted. In dogs with a body weight of about 15 kg or more, examination of the
descending duodenal portion may be possible with this typical endoscope.
Biopsies of the various gastric and duodenal areas are taken and the different
views are photographed.
Endoscopy of colon and rectum is
performed under general anesthesia, as mentioned above, after fasting for some
48 hours. Prior to the examination the colon and rectum are cleansed with a
water enema. The endoscope is introduced through the anus via a speculum. With insufflation
of air, the rectum of colonic canal is followed proximately, if possible to the
caeca and ileac region. Examination of the colon and rectum is best performed
while the probe is being withdrawn. Biopsies of various areas are taken and
different views are photographed.
DIFFERENT
ENDOSCCOPIC CHARACTERISTICS OF GIT DISEASE
Endoscopy is useful in the diagnosis of some of the gastrointestinal
diseases only and is contraindicated in some conditions like gastro esophageal
reflux and mega esophagus.
Esophageal
disorders
The endoscopic examination of the esophagus is
applied with principal indications of dysphagia and regurgitation. The functional disorders of esophagus are
studied with radiographic examination instead of endoscopic examination.
Foreign body
obstruction is not uncommon in dogs particularly in the terrier breeds (rather
than cats) because the esophagus is a highly distensible organ. Ulcerative
esophagitis is result of esophageal foreign bodies and must
be treated as a matter of urgency.
Endoscopic forceps are very helpful in
the removal of the foreign body in many animals, provided the entity is minor
and restricted in the cervical or cranial thoracic region, and the risks of
perforation are low. Esophagitis follows inflammation resulting from various affronts,
both acute and chronic. The most common causes of esophagitis
are persistent esophageal foreign bodies, ingestion
of acidic substances, persistent vomiting. Peptic esophagitis and reflux
esophagitis are far less obvious on endoscopy and vary in severity. Erythema or
erosions may be seen, particularly in the distal esophagus. In severe cases,
the erosions may progress to ulceration and stenosis may result.
Strictures following reflux esophagitis may also
present as diffuse or strip-like areas of erosion or generally occur in the
form of a regular, concentric narrowing of the lumen,. Successive inflation of
balloon catheters introduced via the operating channel of the endoscope helps
in the alleviation of the strictures. Strictures occur following ingestion of acidic
substances are often far-reaching and carry a very guarded prognosis and it
makes the treatment unsuccessful.
Gastric
disorders
Indications for gastric endoscopy are chronic vomiting, hematemesis, melena,
or severe anemia as a consequence of gastrointestinal bleeding. Acute
gastritis is a vague clinical entity associated with loss of integrity of the
gastric mucosa. Various etiological agents may be associated with acute
gastritis for example, ingestion of a foreign body or caustic materials and
infectious disease. Reflux gastritis is usually chronic, but occasionally it
may present as an acute syndrome. It follows retrograde movement of irritant
biliary and pancreatic secretions which may disrupt the mucosa to cause erosions,
particularly on the top of the mucosal folds in the antrums.
Metabolic disorders and hepatic diseases may
result in ischemia of the gastric mucosa. The ischemia is visualized as
multiple hemorrhagic mucosal erosions. Chronic gastritis may cause vomiting,
weight loss and anorexia. Endoscopic examination and endoscope-guided biopsy
have revealed three basic patterns of chronic gastritis. Atrophic type of
chronic gastritis is characterized by abnormally pale mucosa with visible sub-mucosal
blood vessels and atrophy of the fundic folds.
Nodular type of chronic gastritis is characterized
by a papular or nodular reaction, often around the pylorus. Granulomatous type
of chronic gastritis is characterized by diffuse or localized hypertrophy of
mucosa of antral region which is called chronic hypertrophic pyloric
gastropathy or antral pyloric hypertrophy. Pyloric obstruction is a relatively
common disorder and results from congenital or acquired stenosis or blockage of
the pyloric lumen by a foreign body. CHPG is most common
in older, small breed dogs.
It is characterized by the appearance of a diffuse
or localized hypertrophy of the anteropyloric mucosa which results in delayed gastric
emptying. The clinical signs include chronic vomiting and weight loss. The
possibility of visualization of almost pathognomonic hypertrophy may be in the
pyloric region, it must be differentiated from neoplastic conditions by biopsy.
Congenital pyloric stenosis appears most commonly in Boxers, French Bulldogs,
and Boston Terriers, and has an endoscopic appearance that is similar to CHPG. Gastric
ulceration appears to be much more common than was supposed before the
widespread use of endoscopy.
Gastric ulceration may reflect a variety of
etiologies, such as systemic illness or the use of ulcerogenic drugs
(particularly nonsteroidalanti-inflammatory agents). Ulcers that occur as a
consequence of these drugs are often small, concentrated in the antropyloric area
and appear as linear or lenticular erosions with adjacent, often multiple, superficial
bleeding points. Gastric tumors may be either benign or malignant. Many benign gastric
tumors are discovered serendipitously at endoscopy. Benign, adenomatous polyps
may occur in the antrum and may cause pyloric stenosis. In contrast, leiomyoma’s,
typically found in older dogs; appear as ulcerated masses, frequently in the
fundus and occasionally at the gastro esophageal junction. Malignant gastric neoplasia
in dogs is usually a carcinoma or adenocarcinoma, whereas lymphoma is the most
common tumor type in cats. Endoscopically, these gastric neoplasms are
pleomorphic.
The principal indications for endoscopy of the
proximal intestinal tract are chronic vomiting, small intestinal-type diarrhea,
and putative malabsorption syndromes. The use of endoscopic catheters to
collect duodenal chyme for quantitative bacteriological culture is essential for
definitive diagnosis of small intestinal bacterial overgrowth. Endoscopic
examination of the intestinal tract may reveal evidence of hyperemia or ulceration,
but it is not easy to correlate these signs with disease. In many cases with histopathologically
confirmed disease, the endoscopic appearance is normal.
There are no pathognomonic presentations of
intestinal disease, and in most cases histopathological examination of biopsy material
is necessary to make a diagnosis. Intestinal (duodenal) ulceration is rare in
animals. When it does occur, it is generally associated with chronic inflammatory
bowel disease or neoplasia, and is often situated close to the pylorus.
Intestinal ulcers may perforate, resulting in acute abdominal crisis. Lymphangiectasia
presents endoscopically with a multi-focal, pale, papular, almost granular
appearance. The mucosa may sometimes have a mucoid appearance due to exudation
of lymph nodes.
Intestinal tumors are not readily diagnosed by
endoscopy, although occasionally a friable, hemorrhagic mass may be seen. Most
commonly a thickening or swelling is noticed and histopathological examination
of biopsy samples is necessary to make the diagnosis.
Large intestinal
and colorectal disorders
Colonoscopy is necessary if the distal intestinal
tract is to be visualized. The principal indications are large bowel diarrhea,
tenesmus, and hematochezia . As with the investigation of gastric and small
intestinal disorders, it may prove difficult to correlate histopathological
evidence of disease with endoscopic appearance, and the clinician must be
prepared to take serial biopsy samples from the area under investigation. Colitis
may result in discontinuous lesions interspersed between areas of
endoscopically normal mucosa, although it is most often diffuse. Lesions may be
superficial or extend deep into the sub mucosa. Healing of these deeper lesions
causes fibrosis that result in stenosis and formation of pleomorphic pseudo
polyp. Chronic inflammation may result in thickened, excessively folded,
friable mucosa.
Histological classification of representative
lesions, and of apparently normal mucosa, is mandatory. Ileocolic
intussusception is not uncommon, particularly in young animals with intestinal
motility disorders accompanying diarrhea. It appears endoscopically as a
smooth, intraluminal mass. Whip worm infection is associated with Trichuris
vulpis, a parasite with a widespread distribution. However, the
routine use of gastrointestinal endoparasiticides removes these parasites and
thus clinical disease is regional. Trichuriasis is associated with tenesmus,
hematochezia, and the presence of colonic inflammation of varying degrees of
severity
Colonic and rectal neoplasia may be benign or
malignant. The most common manifestation is benign polyp formation, which has a
pleomorphic presentation. These polyps may protrude through the rectum and
cause tenesmus and bleeding. Malignant tumors also have a pleomorphic
presentation, dependent to some extent on the underlying type and size.
Stenosis may result if they are large.
CONCLUSIONS
Endoscopy
has proved to be a very valuable and useful tool in the diagnosis of
gastrointestinal diseases in the dogs. The use of endoscopy is limited mainly
to specialized clinics. It is mainly indicated in dogs with signs of chronic
gastrointestinal disease, in which a diagnosis cannot be made with the available
diagnostic tools.
1. Tams, T. R. Small Animal Endoscopy. St
Louis: The CV Mosby Company, 1990: 417.
2. Simpson,
K. W. Gastrointestinal endoscopy in the dog. Journal of Small Animal
Practice
1993; 34: 180–188.
3. Sullivan,
M., Miller, A. Endoscopy of the oesophagus and stomach in the dog with persistent
regurgitation and vomiting. Journal of Small Animal Practice 1985; 26:
369–379.
4. Lecoindre
Pan Atlas of gastrointestinal endoscopy in dogs and cats.
5. Edward J Hall, James W. Simpson, David A Williams
BSAVA manual of canine and feline gastroenterology.
No comments:
Post a Comment