B
Barium Enema
CONTRAINDICATIONS
Note: Organic iodine contrast material (e.g., sodium iothalamate, sodium diatrizoate, diluted 1 : 1 with water) should be used instead of barium if rectal or colonic perforation is suspected; contrast effect will be reduced, however (see p. 1284).
EQUIPMENT
• General anesthesia is usually required; otherwise, barium is often expelled from the rectum by the animal’s straining.
• Foley urinary catheter (e.g., 10-18 Fr tube for body range of cats to large dogs, respectively) or Bardex catheter
PREPARATION: IMPORTANT CHECKPOINTS
• Fecal occult blood testing is highly specific using O-tolidine-based test kits and may be performed to further increase an index of suspicion for a colonic abnormality.
• Prepare an adequate volume of barium. Using too low a barium dose is a very common problem, causing pseudolesions or missing lesions altogether.
• Barring excessive anal pain, any dog weighing 6 kg or more needs to have a simple but complete rectal palpation prior to barium enema to better localize any focal lesions.
• A maximum amount of feces is evacuated from the colon prior to the administration of the barium enema.
• Metastasis imaging (three-view thoracic radiographs; abdominal ultrasound to assess liver, lymph nodes, etc.) is indicated if malignancy is part of the differential diagnosis.
PROCEDURE
• Obtain preliminary abdominal radiographs to confirm adequate animal preparation (colon is as empty as possible) and to set radiographic technique. The barium contrast dose of 10 mL/kg is placed into enema reservoir.
• Lubricate catheter and insert sufficiently such that Foley balloon is well beyond the anus and within the rectum.
• Inflate Foley balloon to reduce or prevent outflow of contrast from the anus, and gently tug on catheter to bring Foley balloon to seal caudally and prevent contrast leakage from anus.
• Slowly administer barium, with the animal in right lateral recumbency, using gravity for colonic filling (raise the reservoir above the animal).
• Once the colon has been distended, clamp the infusion tubing to prevent backflow of the contrast material.
ALTERNATIVES AND THEIR RELATIVE MERITS
• Abdominal ultrasound: the potential for visualizing the structure of the colonic wall is often severely restricted by the pelvis and by presence of air in the colon.
• Plain radiographs: diagnostic test of choice for bony obstruction of the pelvic canal (fracture, malformation, mass); poor sensitivity for soft-tissue lesions of the colon
• Colonic biopsy: diagnostic test of choice once a focal or diffuse mucosal lesion is suspected or identified
Barium Esophagram, Dynamic
PREPARATION: IMPORTANT CHECKPOINTS
• Personnel needed for procedure (restraint and administration of contrast). This may require two to three people, depending on animal’s size and temperament.
POSSIBLE COMPLICATIONS AND COMMON ERRORS TO AVOID
• Aspiration of contrast agent: study is always begun with a liquid contrast agent and no food. Animals with disorders requiring these evaluations may be prone to dysphagia and aspiration of contrast. If a small amount of liquid contrast agent is aspirated, it can be coughed up. If the animal aspirates a substantial amount of liquid contrast agent, the study should be aborted.
• Ionic iodinated contrast agents: these agents should not be used because clinically significant (potentially fatal) pulmonary edema can occur if they are aspirated. Ionic agents include diatrizoate, iothalamate, and iodamide compounds. All must be avoided.
• Nonionic iodinated contrast agents: these agents can be used if esophageal perforation is suspected.
• Leakage of contrast agent: evidence or risk of esophageal perforation is considered a contraindication for this study. If contrast agent leakage is suspected at any time, the study should be aborted.
• Assuming the procedure is not stopped because of aspiration of contrast agent or evidence of leakage of contrast agent, it is important to perform the study with both liquid contrast agent and liquid contrast agent mixed with food to give as full an assessment of esophageal function as possible.
PROCEDURE
• Position animal in right lateral recumbency (if a C-arm fluoroscopy unit is used, it may be possible to place the animal in sternal recumbency and use a horizontal beam) with appropriate restraint.
• Administer liquid barium PO (∼5 mL for a cat and 5-10 mL depending on the size of the dog), and activate fluoroscopic unit. Image the oral and pharyngeal phases of swallowing (progression of barium from mouth to esophagus) and esophageal transit (progression from upper esophageal sphincter to stomach). Repeat two to three times even if no abnormality is defined.
• Administer barium and canned food mixture PO. Appropriately sized food balls (1-3 cm in diameter) may be fed to the animal or placed in the mouth. Activate fluoroscopic unit, and image the oral and pharyngeal phases of swallowing (progression of barium and food from mouth to esophagus) and esophageal transit (progression from upper esophageal sphincter to stomach). Repeat two to three times even if no abnormality is defined.
Dynamic esophagram, iodinated contrast agent:
• This study may be performed if esophageal rupture is suspected or if endoscopy is to be performed immediately following the esophagram. If an esophageal perforation is suspected, a static esophagram is usually performed instead, using a nonionic iodinated compound.
Behavioral Assessment
PROCEDURE
The specific overall goal is to determine the exact nature of the problem, resulting in appropriate intervention and prognosis when possible. With the increased use of electronic communication, sending and receiving histories before the consultation is a convenient and time-saving strategy. A sample set of history forms can be found at www.vet.cornell.edu/abc. Note: Many owners are more willing to divulge behavioral information to technicians than to veterinarians. In addition, the technician can demonstrate training procedures and behavior modification techniques.
1. Rule out medical disorders (e.g., urinary tract infection, feline lower urinary tract signs/disease, or ectopic ureters for soiling an area in the house; metabolic, central neurologic, endocrine, or pain-producing conditions for aggression), and treat appropriately if present.
3. Clarify the reaction of the owners and others to the animal’s misbehavior. Do they punish or soothe the animal?
4. Help the owner to avoid misdirected intervention, such as punishing after the fact, physically punishing the dog for aggressive behavior, or rewarding jumping up.
5. The owner should be given a reasonable treatment plan that does not involve risk to the owner or the public.
• If the dog was obtained from a kennel at 6 months of age, it may neither have been house broken properly nor socialized to people during the socialization period of 7-14 weeks of age.
• If the dog was obtained as a 3-week-old puppy or was hand raised, it may be too dependent on people and not properly socialized with dogs.
• If the dog was obtained from a pound or an animal shelter, it may have been placed there because it was destructive or aggressive in the original home.
7. Note: Canine aggression is much more complicated. The victim, time, place, and circumstances of the aggressive episode must be known. The owner should be asked to describe the dog’s posture: the position of its ears and tail as well as its vocalization and mouth position. Pupillary dilation and raised hackles indicate sympathetic stimulation. A temperament test should be performed. A toddler-sized doll can be walked toward the dog. Although some dogs are frightened, aggressive ones will bark at, and even bite, the doll. An artificial hand (Assess-a-Hand) can be used for determining how responsive the dog is to touching of its head, abdomen, paws, and tail. The artificial hand can also be used for pulling food from the dog in a safe manner.
Biopsy: Ultrasound-Guided Percutaneous
EQUIPMENT, ANESTHESIA
POSSIBLE COMPLICATIONS AND COMMON ERRORS TO AVOID
• Avoid overly rapid advancement and activation of the instrument:
○ A common, serious error of inexperienced veterinarians is to both advance and activate the instrument in one motion, which is contraindicated (poor placement/control of instrument tip).
• Identify and avoid large vessels in the organ being sampled or in those adjacent to the structure to minimize hemorrhage.
• Avoid penetrating bowel lumen, especially with larger-gauge instruments, owing to risk of peritonitis.
• Ensure that the ultrasound beam captures the full length and orientation of the instrument in the animal (see p. 1275).
• Sample the left aspect of the liver when possible to avoid the gallbladder and hilar vessels on the right. If the liver is small or cranially located, consider a caudal intercostal approach.
• In cases of bilateral renal abnormalities, the left kidney should be sampled because of its more caudal location.
• Avoid using preanesthetic drugs that cause splenomegaly or panting whenever possible (e.g., acepromazine/phe-nothiazines, hydromorphone/opiates, respectively).
PROCEDURE
• Thoroughly evaluate area of interest sonographically, characterize lesion, identify adjacent or internal vessels to be avoided, and determine least traumatic location and direction of needle placement.
• Automatic:
○ Note the throw length of the biopsy device before triggering it. This is the additional distance the instrument advances when triggered.
○ Manually advance the needle, stopping at this distance superficial to desired biopsy site. Caution: When triggered, needle will advance the full predetermined throw length to obtain biopsy.
POSTPROCEDURE
• If small amount of hemorrhage is noted, reevaluate after several additional minutes, ensuring that the patient is monitored (mucous membrane color, blood pressure) and is kept recumbent with the biopsied side down (e.g., sternal recumbency if a liver biopsy was near or on the ventral midline).
Blood Pressure Measurement
OVERVIEW AND GOALS
• The goal of noninvasive blood pressure (BP) assessment in animals in a veterinary setting is to accurately measure arterial BP and detect abnormal BP, particularly systemic hypertension.
INDICATIONS
• Presence of systemic disease known to be associated with systemic hypertension (e.g., renal disease, hyperthyroidism, hyperadrenocorticism, diabetes mellitus, pheochromocytoma)
EQUIPMENT, ANESTHESIA
Doppler method (used in dogs and cats; the preferred method for cats):
• Hair clippers and isopropyl alcohol, if desired, for preparation of site of piezoelectric crystal application
Oscillometric method (automated system; used in dogs, less reliable in cats):
PREPARATION: IMPORTANT CHECKPOINTS
• Be sure the animal has acclimated to the clinic’s environment and is calm and comfortable in lateral or sternal recumbency or sitting. BP values may be obtained in standing animals only if a tail cuff is used. Owner presence and assurance may help calm the animal.
• Be sure the cuff size used is appropriate and noted in the record for future reference. The width of the cuff should be (40% of the circumference of the limb or tail at the cuff site.
• During measurements with either method, the cuff should be at the level of the right atrium. This may involve elevating a forelimb during measurement if the animal is sitting.
POSSIBLE COMPLICATIONS AND COMMON ERRORS TO AVOID
• Erratic oscillometric readings may be obtained if an arrhythmia or very high heart rate is present.
• Turn volume knob to low or zero before turning Doppler amplifier on; then gradually increase volume to search for the pulse after contact is established between the crystal and the patient’s skin. Failing to do this can produce extremely loud static noise that is startling to the patient (if using speakers) or deafening to the operator (if using headphones).
PROCEDURE
• Restrain the animal in a comfortable position, and allow time and reassurance for acclimation. The position of the animal is dependent on the animal’s temperament and mobility and on the planned position of the cuff.
• Measure the circumference of the limb or tail at the intended cuff site, and select an appropriately sized cuff (as already described when preparing the animal).
• Clip or dampen hair as needed at site of Doppler crystal application distal to the cuff (palmar or plantar arterial arch, proximal to the metacarpal/metatarsal pad and slightly medial); apply coupling gel, and hold or tape crystal in position.
• The crystal is placed against the skin concave side down; the flat aspect of the crystal faces out.
• Turn volume knob to low setting, and turn amplifier on. Verify correct position of crystal by listening for clear pulsatile sounds of flow in the artery beneath the crystal. Adjust the crystal position or angle as necessary to improve signal strength if sounds are soft, distant, or muffled.
• While listening to sound of flow, inflate the cuff using the bulb manometer to approximately 20 mm Hg greater than the pressure needed to cut off flow sounds.
• Slowly deflate the cuff (1-3 mm Hg per second), and note the pressure at which pulsatile sounds of flow recur. This pressure is recorded as the systolic pressure.
• Completely deflate the cuff, and count the heart rate in the approximately 30 seconds between pressure readings. A contemporary heart rate can be recorded with each BP reading.
• Record at least 6 measurements in succession, allowing approximately 30 seconds to 1 minute between measurements to allow for limb reperfusion.
• Discard the first reading, and average the results of the remaining readings to obtain a representative number of systolic pressure and heart rate. High heart rate may indicate that increased levels of stress have affected readings.
• Restrain the animal in a comfortable position, and allow time and reassurance for acclimatization. The position of the animal is dependent on animal’s temperament and mobility and on the planned position of the cuff.
○ Cuff on distal hind limb at level of metatarsus (median artery): lateral recumbency preferred; sternal recumbency may be used if leg is in gentle extension during measurement.
○ Cuff on proximal tailhead: sternal or lateral recumbency or standing if animal is relatively immobile during readings (tailhead is preferred cuff site for oscillometric measurement technique in cats).
• Measure the circumference of the limb or tail at the intended cuff site, and choose an appropriately sized cuff (as already noted when preparing the animal).
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