Page 331 - Feline diagnostic imaging

21.2 Contrast adiography 339
has been made. The stomach should be empty or contain Segmental contractions are more obvious in cats than in
only a coating of barium at this point. Although barium dogs and the duodenum may have a “string of pearls”
reaches the colon, the study should not be relied upon for appearance (Figure 21.7). Lymphoid follicles (Peyer’s
diagnosis of colonic disease. There may be remaining patches) appear similar to ulcers but are more symmetric,
material in the colon and the colon may not be adequately causing them to be referred to as “pseudo‐ulcers.” Barium
coated or distended. will be in the colon at 30–60 minutes and by 90 minutes,
Problems that result in a poor study include poor prepa- most of the barium will be in the colon. The cecum is non-
ration, inadequate dosage and failure to expose enough sacculated and has the shape of a comma. Normally the GI
films to allow recognition of persistence of lesions. The tract is continuously moving. True anatomic abnormalities
most common complication is aspiration of barium. will persist from one film to another. Repeatability helps to
Material in the trachea and main bronchi is usually confirm that a suspected lesion is real and is not secondary
coughed up but barium that reaches the alveoli will be to a temporary contraction.
retained. Because barium is inert and nonirritating, aspira- Unless a foreign body or mass is identified, most GI
tion of a small amount of barium is generally not life series do not yield a specific diagnosis but anatomic disease
threatening and adverse clinical signs are usually not seen. may be identified and the extent, location, and nature
The barium will be walled off and will remain visible on (mucosal or infiltrative, focal or diffuse, obstructive or non-
radiographs years later. Aspiration of a large amount of obstructive) of lesions might be noted.
barium such as that delivered by a gastrointestinal tube is
deadly.
Occasionally, administration of barium is made difficult 21.2.6 Contrast Studies with Iodinated
by an excited, frightened, or intractable patient. Sympathetic Contrast Media
stimulation can alter GI motility. If sedation becomes nec- Iodinated contrast media should be used for management
essary, drugs should be used that do not have a strong effect of PEG tubes or if perforation is suspected because barium
on GI motility. Ketamine/diazepam has been suggested. can cause a severe granulomatous response in the perito-
neal cavity [4]. It is also useful for esophagography if the
integrity of the esophagus is in question (Figure 21.8). For
21.2.5 Normal Gastrointestinal Series
cats, nonionic iodinated contrast is preferred over ionic
Gravity should be relied on to fill various portions of the contrast. Iodinated contrast is not used for routine studies
stomach (Figure 21.7). In right lateral recumbency, there because it does not coat the mucosa as well as barium and
will be maximum filling of the pylorus with barium while has a slightly blurred appearance compared to barium. In
some gas may be seen in the fundus. In left lateral recum- determining the amount of contrast to administer, both the
bency, gas may be seen in the pylorus while barium runs by amount of iodine per body weight and the total volume
gravity into the fundus. For the dorsoventral projection need to be considered. First, calculate the amount of iodine
(sternal recumbency), the body of the stomach will be as 600–800 mg iodine per kg. Calculate the total volume as
closest to the cassette and will have maximal filling with 10 mL per kg and dilute the iodine with sterile water to the
barium. For the ventrodorsal projection (dorsal recum- required volume [3]. The contrast is then given orally.
bency), gas may be present in the body of the stomach.
Most cats will have a J‐shaped appearance with the pylorus 21.2.7 Pneumogastrogram
on or to the right of the midline. A few cats will have a
stomach that extends further across to the right side. A pneumogastrogram is a negative contrast study of the
Gastric emptying and intestinal transit are faster in cats stomach performed by passing a nasogastric tube into the
than dogs, necessitating more frequent exposures over a stomach and inflating the stomach to slight‐to‐moderate
shorter period of time. All four projections should be degree. The procedure can be done to screen for a foreign
obtained immediately after administration of barium con- body or to determine the position of the stomach.
trast. Right lateral and ventrodorsal projections should be Preparation is usually minimal prior to the procedure.
made at 15, 30, and 60 minutes after the start of the proce-
dure. Subsequent exposures should be made at 30‐minute
intervals until the study is complete. 21.2.8 Double-Contrast Gastrogram
As barium proceeds through the small intestine, the A double‐contrast study requires preparation similar to that
contrast column should be continuous, sometimes referred of a barium series because the stomach should be empty to
to as a ribbon. Intestinal villi cause the margins of the allow for coating of the gastric mucosa with barium.
contrast column to be slightly irregular or “feathered.” 10–20 mL of barium is administered before inflating the