Gastrointestinal Special Procedures in Veterinary Radiography

Transcription

Gastrointestinal Special Procedures in
Veterinary Radiography
CVM 6104, Spring Semester
Kari L. Anderson, DVM, Diplomate ACVR
Office: C350 VTH, Phone: 5-3762
kla@umn.edu
(additionally, you can often find me in radiology!)
Objectives:
1. Be able to answer questions pertaining to properties of GI contrast media.
2. Be able to list, or select from a list, specific indications for the GI special
procedures.
3. Be able to list, or select from a list, contra-indications for the GI special
procedures.
4. Be able to list, or select from a list, possible complications for the GI special
procedures.
5. Be able to answer questions pertaining to the technique, including
contrast/dose/views obtained, of the following GI special procedures:
esophagography, gastrogram/upper GI series, pneumocolon, barium enema.
6. Be able to answer questions pertaining to expected normal morphology,
emptying times, transit times, variations of normal, and species differences.
7. Be able to describe or answer questions pertaining to basic interpretation of
the abnormal study as presented in class.
8. Be able to asses a case presented with historical and physical information and
determine next appropriate imaging of the GI track, as well as offer basic
interpretation of the abnormal findings described.
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GI Contrast Media
Barium sulfate:
Barium sulfate is the contrast media of choice for gastrointestinal studies. The
barium sulfate preparation must be dense (for appropriate radiopacity) but flow easily,
must not foam, and must coat the mucosa evenly without artifacts. One should purchase
a commercially available preparation of barium sulfate. Commercially available barium
sulfate suspensions contain suspending agents, deflocculating agents, preservatives, and
flavoring agents.
Various gastrointestinal procedures utilize varying concentrations of barium
sulfate suspension. There are two different systems used to measure barium sulfate
suspensions:
1. Weight-to-volume
A certain weight of barium sulfate is added to enough water to obtain a
predetermined total volume.
Example: A 15% w/v suspension is prepared by adding 15g of barium sulfate
to enough water to obtain a total volume of 100ml.
2. Weight-to-weight
A certain weight of barium sulfate is added to enough water to obtain a
predetermined total weight.
Example: A 15% w/w suspension is prepared by adding 15g of barium sulfate
to 85g (85ml) of water to obtain a total weight of 100g.
The medical imaging department purchases a 100% w/v (56% w/w) suspension. This is
too dense (opaque) for general gastrointestinal use; therefore it is diluted 50:50 with tap
water.
Barium sulfate is also available in a paste, which is a thicker creamy suspension
of barium sulfate. This will adhere more readily to the mucosa, and is often used for
esophagography. The medical imaging department purchases a 70% w/v (44% w/w)
preparation that is used without dilution. This preparation is “pleasantly flavored” and
also contains artificial sweetener.
Iodinated contrast:
Water-soluble, iodine-containing contrast agents may be used for gastrointestinal
imaging in certain instances. Generally, this contrast may be chosen in cases of
suspected esophageal or gastrointestinal perforation.
Ionic iodinated contrast compared to barium sulfate
More expensive!
Hyperosmolar, thus will tend to draw fluid into the intestinal tract
» May cause or worsen dehydration (thus a lower dose is given)
» Dilutes the contrast for the GI series
» Can lead to fulminate pulmonary edema if aspirated
More likely to cause emesis
Has a more rapid transit through the intestinal tract due to irritation (shorter
emptying and transit times, thus a shorter study)
Small leaks can be difficult to visualize
The use of non-ionic iodinated contrast will have fewer of the above as these
solutions are not as hyperosmolar (but even yet more expensive).
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Esophagography
Definition:
Esophagography is the radiographic study that may permit evaluation of both esophageal
function and morphology. The study is best performed under fluoroscopic examination,
which allows the dynamic process of swallowing to be studied. This study is termed a
dynamic, or real-time, esophagogram. Conventional radiographic examination permits a
static momentary picture of the function of the esophagus. Multiple serial static
radiographs, or static esophagogram, may provide much information. A properly
performed conventional esophagogram (without the assistance of fluoroscopy) can
provide all the information needed on location, luminal size, shape, content, and integrity
of the esophagus.
Indications:
1. Further evaluation and definition of survey radiographic findings.
2. History of regurgitation, dysphagia, salivation, gagging, painful swallowing.
3. To outline lesions of the esophagus (masses, esophagitis, diverticula, strictures,
perforations, foreign objects).
4. To evaluate location of esophagus relative to conditions in the immediate vicinity
(cervical, mediastinal, pulmonary masses).
5. To study swallowing difficulties and motor dysfunctions (need fluoroscopy for
dynamic studies).
Contra-indications:
1. A dilated, fluid- or food-filled esophagus usually has sufficient contrast to
preclude the necessity for esophagography. The contrast material may be diluted
and a poor study obtained. This is not necessarily a contra-indication.
2. A patient with severe regurgitation/dysphagia is predisposed to aspiration of the
contrast. Small amounts of barium sulfate aspirated into the lungs usually have
no consequences, unless this is superimposed on severe lung disease. Aspirated
ionic iodinated contrast may cause fulminate pulmonary edema (use non-ionic).
3. If an esophageal perforation is suspected, iodinated contrast material should be
used. Barium sulfate can incite a severe granulomatous reaction in the
mediastinum.
Complications:
1. In a patient with swallowing disorders, megaesophagus and other esophageal
diseases, there may be an increased risk of aspiration of contrast.
2. If there is an esophageal perforation, barium sulfate can incite a severe
granulomatous reaction (use iodinated contrast if this is suspected). However,
iodinated contrast does not always demonstrate a small leak, and a negative study
for suspected perforation should be followed up with a routine barium swallow.
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Contrast Media Used/Dose:
A. Barium cream or paste is often the preferred contrast medium because it adheres
to the mucosal surface of the esophagus and allows the recognition of both gross
abnormalities and fine mucosal details. Radiographs can be made after passage of
the bolus.
B. Liquid barium suspensions fail to adhere to the mucosal surface and leave little or
no traces once the bolus has passed into the stomach. Thus, radiographs must be
made during the passage of the bolus. Liquid barium will often demonstrate
megaesophagus, foreign bodies, and masses.
C. Liquid barium suspension mixed with wet food and different sizes of dry kibble
may be used to demonstrate distensibility, regional motility disorders, and early
strictures that may allow liquid and paste to pass unhindered.
D. Iodinated contrast material should be used in suspected cases of perforation. This
is not recommended for routine use because of poor coating ability secondary to
low viscosity.
E. Approximately 5-20 ml of the selected contrast material is given to induce several
complete swallows for coating the pharynx and esophagus.
Preparation:
The only preparation needed is to fast the patient for 4-6 hours. This will allow for the
stomach to empty and may also increase the cooperation of the patient (hungry).
Sedation should be avoided as sedation generally affects esophageal transit time and
motility pattern.
Technique:
1. Survey radiographs should always be obtained immediately prior to
esophagography (lateral and VD view of thorax, lateral of neck)
Selection of suitable technique
Assessment of esophagus and surrounding tissues
2. Most sedatives, tranquilizers, and general anesthetics will affect motility and
possibly morphology of the esophagus (i.e., cause dilatation), so routine use is
contra-indicated. A fractious patient may be given a nominal amount of
phenothiazine tranquilizer.
3. For static esophagography, administer contrast material immediately prior to
making the radiograph, and repeat administration each time before a new
radiograph is made. Paste is spread on the hard palate and the mouth held closed
until patient swallows. Liquid is instilled into the buccal pouch and the mouth
held closed until the patient swallows.
4. Obtain lateral and left ventral to right dorsal oblique views (on a VD view, the
esophagus is superimposed over other midline structures). You may also take the
right dorsal to left ventral oblique view (DV oblique)
5. Obtain serial radiographs (repeating administration of contrast) until the entire
esophagus is demonstrated from the oropharynx proximally to the stomach
distally.
6. When barium soaked canned food and kibble is to be used, perform the
esophageal study with liquid barium first.
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Normal Interpretation:
The normal oropharyngeal region will have coating of the mucosa without
significant retention of contrast. A small amount of contrast may remain in the
valleculae and cranial esophagus. No contrast material should persist in the upper
airway or piriform recesses.
The normal esophageal mucosa appears as a series of longitudinal folds. These
folds may separate slightly at the thoracic inlet.
The mucosal surface should be smooth.
The caudal third of the esophagus in cats has a scale-like or transversely striated
pattern (“herringbone”).
In patients with a short neck, particularly puppies, the redundant esophagus may
form a fold or a sacular dilation which should not be mistaken for a diverticulum.
Normal location:
» On midline dorsal to the larynx
» To the left of the trachea in the lower cervical region and thoracic inlet
» Dorsal to the trachea and to the right of the ascending aorta in cranial thorax
» Near midline in the caudal thorax (as it passes dorsal to tracheal bifurcation)
DOG
CAT
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Abnormal Interpretation:
Retention of contrast or contrast/food in the oral pharynx suggests an
oropharyngeal disorder
Reflux of contrast or contrast/food into the nasopharynx may indicate failure of
the soft palate to close the nasopharynx or may indicate incoordination between
pharyngeal muscle contraction and closure of the nasopharynx by the soft palate.
Aspiration of contrast or contrast/food may indicate an abnormal larynx or
incoordination between pharyngeal contraction and relaxation of the
cricopharyngeal muscles.
Classification of lesions into extramural, mural, or intraluminal is helpful.
Infiltration of the wall (mural lesion) by neoplastic, inflammatory, or granulation
tissue usually distorts the mucosal surface, obliterating the longitudinal or oblique
folds and causing mucosal irregularity. Lesions may be circumferential or
eccentric. Small amounts of contrast may be trapped. Thickening of the
esophageal wall may also be demonstrated (only in the thoracic region). Mural
lesions rarely cause obstruction, but may cause focal distension from associated
dysmotility.

Esophageal foreign bodies (intraluminal lesion) will be demonstrated by a fillingdefect within the contrast, or by retention of contrast around the margins. Often
there is associated distension of the esophageal lumen. Foreign bodies may lodge
at the thoracic inlet, dorsal to the base of the heart (most common), or at the
cardia.
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Pedunculated esophageal masses may also show as filling-defects within the
contrast (intraluminal lesion). Obviously, one side of the mass will be continuous
with the esophageal wall. The mucosal surface may be smooth or irregular.
There may be associated proximal distension secondary to partial or complete
obstruction.

Diverticula of the esophagus are most often encountered cranial to strictures, but
may be congenital. Strictures are seen as persistent narrowing of the lumen with
or without associated mucosal irregularity.

Extrinsic esophageal masses (extramural lesion) often cause the esophagus to
gradually deviate around them. These may also cause partial obstruction of the
esophagus with distension.

Esophageal tears will have extravasation of contrast material outside of the
esophageal lumen.
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Upper GI Series
Definition:
The upper gastrointestinal series is the radiographic study of the stomach and small
intestine through the use of contrast material. The exam can provide both morphologic
and functional information, through evaluation of emptying and transit times. The study
generally utilizes positive contrast media; however, both negative contrast and doublecontrast studies of the stomach can also be performed. When only the stomach is
evaluated, the special procedure is known as gastrography.
Indications:
1. Acute or chronic vomiting
2. Hematemesis
3. Anorexia
4. Acute abdominal pain
5. Small intestinal diarrhea or melena
6. Suspicion of complete or partial obstruction (intraluminal or mural lesions)
7. Suspicion of linear foreign body
8. Cranial abdominal mass lesion
9. A need to determine size, shape, and position of stomach or small intestine
10. Suspect intestinal perforation (use iodinated contrast to be safest!)
Contra-indications:
1. If obstructive ileus can be determined on survey radiographs, an upper GI series
will only delay surgery and increase client cost (relative contra-indication).
2. High suspicion of bowel perforation (barium sulfate can cause severe
granulomatous peritonitis).
3. Prior use of drugs that affect intestinal transit time.
4. A morphologic study should not be performed if the stomach is not empty (delay
study).
Complications:
1. In a patient with severe, protracted vomiting, the risk of aspiration of contrast is
increased (vomiting is not a contra-indication to the study).
2. If there is a bowel perforation, barium sulfate can incite a severe granulomatous
peritonitis (consider iodinated contrast if this is suspected). However, iodinated
contrast does not always demonstrate a small leak, and a negative study for
suspected gastrointestinal leakage should be followed up with a routine barium
series. Therefore, as there would be the possibility of misdiagnosis of a small
leak, coupled with the fact that the abdominal cavity can be flushed during
laparotomy, it is recommended to use barium for almost all studies.
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A. Barium sulfate suspension (30% weight/weight) is the contrast medium generally
used.
B. The dose of barium sulfate suspension is 6 ml/lb for both dogs and cats.
C. Iodinated contrast (Gastrografin or any of the formulas for urinary or vascular
studies) should be initial contrast of choice if intestinal perforation is suspected.
D. The dose of iodinated contrast should be decreased to 1-2 ml/lb diluted with
water to obtain a volume of 6 ml/lb.
Preparation:
For an elective study, the patient should be fasted for 12-24 hours in order that the
stomach be empty. An enema the evening prior to, and the morning of, the study should
be given in order to empty the colon. Food and fecal material can cause delay in
emptying and transit times, as well as mimic or obscure abnormalities. For studies
performed to evaluate for obstruction, it is not necessary to have the colon empty.
Technique:
1. Survey radiographs of the abdomen must be performed.
Evaluate intestinal tract and determine the need for an upper GI series
Ensure that the patient is properly prepared
Select appropriate technique
2. Sedation should not be used, especially if the study is to be of a functional nature. If
the patient is intractable, a nominal dose of acepromazine (0.1-3.0 mg) may be given
to the dog. A small dose of ketamine (6 mg/lb) and diazepam (0.2 mg/lb)
combination may be given to the cat. These drugs appear to have little effect on the
transit times of liquid contrast.
3. The appropriate dose of contrast material should be administered via an orogastric or
nasogastric tube. Be sure to use a mouth gag with the orogastric tube.
4. Make lateral and VD views immediately following administration (0-time films) of
the contrast material. If the stomach is the area of interest, also make DV and the
opposite lateral views.
5. The exact timing of following radiographs may depend upon any abnormalities seen
and the transit time of the contrast. In general:
In the dog, make lateral and VD views at 15, 30, 60 minutes, and then hourly until
the majority of the contrast material has reached the distal small intestine and the
colon.
In the cat, make lateral and VD views at 15, 30, 45, 60 minutes, and then every
30-60 minutes until the majority of the contrast material has reached the distal
small intestine and the colon.
6. If iodinated contrast is used, the transit times will be faster.
7. If a double-contrast study of the stomach is to be performed, the stomach may be
distended with air after the majority of the positive contrast has emptied. Make
opposite lateral, VD, and DV views of the stomach. Assess for appropriate gastric
distension.
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Most common technical errors:
1. Improper patient preparation
2. Inadequate dose of contrast
3. Improperly penetrated radiographs (too light)
4. Too few radiographs at too long of time intervals
5. Administration of barium coated dry or wet food
Initial duodenal filling
Complete gastric emptying
SI transit time
SI emptying time
Dog (approx hrs)
By 0.25
2 (0.5-3)
1 (0.5-2)
3.5 (3-5)
Cat (approx hrs)
By 0.2
0.5 (0.25-1)
0.75 (0.5-1)
1. The rugal folds of the stomach appear as relatively radiolucent, linear filling
defects separated by barium in the interrugal spaces. The appearance of the folds
depends upon gastric distension. Rugal folds are smaller and fewer in number in
cats.
2. Gastric contractions should be apparent and should alter the gastric shape over
time.
3. Following contrast administration, gastric emptying should start within 15
minutes, and generally starts immediately. Stress may inhibit gastric movement,
and allowing the patient to calm down in a quiet environment will encourage
emptying to begin.
4. Delayed gastric emptying can also be caused by a low dose of contrast (must
standardize dose), medications, and fecal material in the colon.
5. Barium contrast within the small intestine should be seen in a continuous, ropelike, uniform column. Interruption of the column (segmentation) may be seen
normally, but is frequently an indicator of GI disease.
6. The mucosal surface should be smooth and even or finely fimbriated (fringing at
the barium-mucosal interface – a brush border).
7. The intestinal wall should be thin and uniform.
8. Normal peristaltic waves produce symmetric indentations along the bowel that do
not persist in the same bowel loop on serial radiographs.
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9. “Pseudoulcers” may be seen in the descending duodenum of the normal dog.
These are seen as distinct outpouchings (square or conical) in the antimesenteric
side of the bowel wall and result from the presence of gut-associated lymphoid
tissue. These are more commonly seen in younger dogs. Cats do not have this
finding.
10. In the normal cat, distinct bead-like segments of contrast medium are frequently
seen in the duodenum and proximal jejunum (“string of pearls”). This is due to
strong circular muscle contractions.
11. The normal cat duodenum and/or jejunum may be characterized by a
longitudinally oriented linear filling defect. This appearance is due to an
indentation of a mucosal fold into the lumen and is usually seen in poorly
distended segments (“pseudostring” sign).
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1. Lesions should be repeatable on two views and persistent on serial radiographs.
2. Chronic pyloric obstructive diseases will cause delayed gastric emptying
(pronounced delay with only a small amount of contrast passing in a few hours).
In addition, there will be stringing of contrast into the small intestine. Often,
fluoroscopy is needed to make the diagnosis of pyloric obstructive disease.
The “beak” sign is when barium fills only the entrance of the lumen at the
pyloric sphincter.
The “string” sign is when barium fills the length of the narrowed lumen
through the pyloric sphincter.
The peristaltic pouch is an outpouching of the pyloric antrum along the
lesser curvature.
3. Gastric neoplasia may present as a mass lesion that projects into the lumen as a
filling defect, or as a diffuse, infiltrative mural lesion.
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4. Ulcers produce craters in the wall that appear as outpouchings from the lumen.
The appearance may be variable (differentiate from pseudoulcers). Ulcers may be
benign or malignant.
5. Abnormal position of intestine may be secondary to herniation, abdominal masses
causing displacement, or linear foreign objects or adhesions causing
plication/extensively pleated appearance.
6. Intestinal neoplasia often appears as a focal, annular or “apple-core” lesion with
wall thickening and mucosal irregularity. There may be proximal distension of
the intestine secondary to partial obstruction.
7. Intraluminal foreign objects generally present as filling-defects within the barium.
There may be proximal distension of the intestine secondary to complete or partial
obstruction. If the lesion does not cause complete obstruction, the foreign object
may persist and be seen as a barium-coated luminal object after contrast has
passed.
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8. Severe inflammatory or infiltrative lesions may show numerous nodular filling
defects or “thumbprint” indentations along the mucosal surface. This finding may
be focal or diffuse. Lymphosarcoma may also present this way.
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Pneumocolon
Definition:
A pneumocolon is a study of the large intestine utilizing air as a negative contrast agent.
This study is quick and best used to determine position of the colon relative to the small
intestine and other organs or suspected masses. Some morphology of the large intestine
may be seen, such as large intraluminal or mural lesions; however, small lesions, such as
mucosal irregularities, cannot be studied.
Indications:
1. To determine the location of the large intestine relative to suspected caudal
abdominal or pelvic masses.
2. To differentiate between normal large intestine and dilated gas-filled loops of
small intestine.
3. Possibly to evaluate a suspected lesion such as a mass, stricture, ileo-colic
intussusception, or cecal inversion.
Contra-indications:
None specifically
A. Room air is injected per-rectally as a negative contrast agent
B. The dose is somewhat empirical. Less air may be needed when the information
wanted is only the position of the large intestine. In cats, 20-30 ml may be
injected. In dogs, 60-200 ml may be injected, depending upon size of the patient.
A rough guide would be 3-5 ml/lb.
Preparation:
Generally this procedure is utilized for location of the large intestine, and thus,
preparation is not necessary. An enema could be performed prior to the study.
Technique:
1. Survey radiographs should be made to assess the abdomen and to select an
appropriate technique.
2. Sedation is generally not needed.
3. Place a large diameter balloon-tipped catheter or a catheter-tip syringe into the
rectum.
4. Infuse appropriate amount of air.
5. Make lateral and VD radiographs.
6. Determine the need to repeat the study with more air based upon the radiographs.
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Interpretation:
Interpretation is based upon knowing the normal position of the large intestine.
» The cecum is located to the right of midline at approximately the level of L3.
» The ascending colon is to the right of midline.
» The transverse colon passes from right to left, cranial to the root of the
mesentery.
» The descending colon is generally located to the left of midline and then
courses toward midline when entering the pelvic canal.
» The rectum is located midway between the ventral surface of the sacrum and
the floor of the pelvis on the lateral view. It is on midline on the VD view.
See images for displacements of the colon caused by extracolonic disorders.
As previously mentioned, larger lesions of the colon may potentially be examined
with a pneumocolon. Do not mistake fecal material for intraluminal lesions.
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Barium Enema
Definition:
A barium enema is the study of the large intestine using positive contrast. This study is
morphologic in nature. Studies performed following the oral administration of positivecontrast media do not distend the large intestine and are complicated by the mixture of
contrast with colonic contents and, therefore, are not considered adequate for a large
intestinal study (although, this can demonstrate anatomic location of the large intestine).
A double-contrast study can be performed after the barium enema by emptying the
barium from the colon and then infusing air. This study will provide improved mucosal
detail.
A barium enema should be preceded by complete clinical examination, routine
radiographic study of the abdomen, and rectal and proctoscopic examinations. A barium
enema should not be used as a substitute for rectal examination and proctocolonoscopy.
Indications:
1. To diagnose or confirm the existence of disease.
2. To evaluate the extent of a disorder prior to treatment.
3. Abnormal defecation characterized by excessive mucus or bright red blood
coating the stool.
4. Ribbon-like feces or difficulty defecating secondary to suspected mass or
stricture.
5. Pain or difficulty during defecation.
6. Suspected perforation (use iodinated contrast!).
7. Locate large intestine.
8. Evaluation of specific lesions: mural tumor, extramural mass causing
displacement of colon, ileocolic intussusception, cecal inversion, mucosal lesions.
Contra-indications:
1. Suspected perforation of the colonic wall (use iodinated contrast).
2. Previous colonic biopsy that might have weakened the colonic wall and
predisposed to rupture.
3. Fecal contents that create filling-defects and make evaluation of the mucosal
surface difficult.
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Complications:
1. Possible perforation of the colon secondary to catheterization or over-distension
of a weakened or diseased colon.
2. Barium sulfate contrast that leaks into the peritoneal cavity will incite a severe
granulomatous reaction.
3. Retrograde filling of the distal small intestine. This is not detrimental to the
patient but may hinder evaluation of the colon.
A. Barium sulfate suspension of 10% or 20% weight/weight is generally used. You
will most likely have to dilute the concentration of your available barium sulfate
suspension.
B. Iodinated contrast should be used in cases of suspected perforation.
C. Contrast material should be warmed to body temperature.
D. Dose for a complete barium enema is approximately 3-5 ml/lb injected perrectally. In cats, 20-30 ml should be sufficient. Less contrast may be used if the
position of the colon is the only information wanted.
Preparation:
It is important that the colon be empty of fecal material prior to the study. The patient
should be held off food for 24 hours prior to the study. Ideally, a warm water enema
should be performed the night before and the morning of the study. The enema is used
partially for cleansing and for stimulating defecation. A soapy or cold-water enema may
cause spasm and is thus contra-indicated.
Technique:
1. Survey radiographs should be obtained to assess the colon for preparation and to
select an appropriate radiographic technique.
2. The patient should ideally be placed under a light plane of general anesthesia, or
should be heavily sedated.
3. Insert a large balloon-tipped catheter rectally and inflate the balloon. Consider
cutting off the tip of the catheter to avoid producing colonic spasticity from the tip
contacting the colonic wall.
4. Infuse the contrast material by gravity or by minimal pressure on the syringe. An
enema bag or commercial enema set may be used to infuse by raising the reservoir
slightly above the level of the patient.
5. The contrast material should be infused slowly (over 5-7 minutes) in order to prevent
reflux into the ileum.
6. Make lateral and VD radiographs. Opposite lateral views may provide additional
information.
7. Assess the need for administration of additional contrast material.
8. The contrast can be drained and the colon then infused with air in order to perform a
double-contrast study.
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See information on normal location under pneumocolon.
The normal colon has a uniform diameter when distended.
The mucosal surface should appear smooth and continuous when distended with
barium. There should be smooth coating of the mucosa with barium on a doublecontrast study.
Normal longitudinal mucosal folds may be seen on a double-contrast study.
Normal lymph follicles in the mucosa of the cecum and colon may appear as
spicules on a barium enema study or as pinpoint radiopacities when seen en face
with a double-contrast study (must differentiate from mucosal ulcers). These are
most common in the young dog. These are not commonly seen in the cat.
The normal cat cecum is cone like.
The normal dog cecum is corkscrew or C-shaped.
Filling defects in the barium may be secondary to fecal material or mucus and
would then be a “normal” finding.
Irregularity of the barium-mucosal interface or mucosal ulcerations.
Narrowing of the bowel lumen secondary to spasm or constriction due to
neoplasia, scar tissue or direct trauma to the bowel wall.
Partial or complete occlusion of the bowel lumen.
Outpouching of the bowel lumen due to a hernia or diverticulum.
Displacement of the colon (see images under pneumocolon).
Mural or intraluminal filling defects due to neoplasia. These may have a smooth
or irregular margin.
Assess base and length of defect, the mucosal surface, and the mural involvement
when evaluating a constriction.
An intussusception generally appears as a filling defect within the colon and a
coiled-spring appearance of barium outlining the intussusceptum.
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References
Radiographic Diagnosis of Abdominal disorders in the dog and Cat: Radiographic
Interpretation, Clinical Signs, Pathophysiology, O’Brien, TR ed., Covell Park Vet
Company, Davis, CA, 1981.
Techniques of Veterinary Radiography, 5th ed., Morgan, JP ed., Iowa State University
Press, Ames, Iowa, 1993.
Textbook of Veterinary Diagnostic Radiology, 2nd ed., Thrall, DE ed., W.B. Saunders
Company, Philadelphia, Pennsylvania, 1994.
Thoracic Radiography: Thoracic Diseases of the Dog and Cat, Suter, PF ed., Peter F.
Suter, Switzerland, 1984.