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Radiography is useful for determining the size, shape and position of
organs and lesions both within the body and in relation to one another. (J29.10.w1)
Restraint and positioning
- Proper restraint and correct positioning are essential for adequate
radiographs allowing proper diagnostic interpretation.
(B542.1.w1, B601.5.w5, B602.37.w37)
- It is essential that the patient is immobile while the radiograph is
taken. (J29.10.w1)
- Generally, chemical immobilisation is required.
(B339.1.w1, B601.5.w5, B602.37.w37,
B604.3.w3, J29.10.w1,
J72.49.w1)
- Safe, accurate positioning of the patient is facilitated. (B542.1.w1)
- Motion artefacts are reduced. (B542.1.w1)
- Personnel can remain well away from the area
during radiography. (B339.1.w1)
- It may be possible to obtain lateral and ventrodorsal views using
manual restraint. (B602.37.w37)
- However, it may be difficult to produce good positioning
with the limbs drawn well away from the body.
- Additionally, there is a risk of an unsedated rabbit suddenly
jumping up and off the table.
- Use of "trancing", followed by gentle placement of the
rabbit in lateral recumbency and restraint by use of a long
sandbag over the neck, may allow a lateral radiograph to be taken.
(J513.6.w)
- Note: "trancing", also known as tonic
immobility, is a fear response. Not all rabbits respond to
trancing (B600.3.w3,
J15.29.w2)
and the period of time for which the immobile state is invoked is
variable. (J15.29.w2)
However, use of this may be preferable to inducing anaesthesia
for a short, non-painful procedure. (B600.3.w3)
- Endotracheal intubation is preferable if a lengthy sequence of
radiographs is to be taken.
(B602.37.w37)
- For wild lagomorphs, radiography should be carried out with the animal
under general anaesthesia. (J213.9.w4)
- For details of appropriate chemical restraint, see: Treatment and Care
- Anaesthesia and Chemical Restraint
- Required positioning can be achieved in the anaesthetised rabbit
using sandbags, radiolucent tape and foam wedges. (B542.1.w1)
sandbags and limb ties may be used. (J72.49.w1)
- Thorax:
- Lateral view - place the rabbit in right lateral
recumbency on the cassette. Extend the pelvic limbs using a
sandbag or tape. Extent the thoracic limbs fully and tape them
to the cassette in an extended position, using radiolucent
tape. Gently extend the neck. (B542.1.w1)
- Dorsoventral view - place the rabbit on the cassette in
ventral recumbency. Extend the thoracic limbs cranially and secure
them with tape close to either side of the head, to minimise
superimposition of the scapulae and associated musculature
on the cranial thorax. Extend the pelvic limbs caudally and secure
with a sandbag. Position the ears to minimise their
superimposition on the thoracic cavity. (B542.1.w1)
- Abdomen:
- Lateral view - place the rabbit in right lateral
recumbency on the cassette. Extend the pelvic limbs caudally
and the thoracic limbs cranially, holding them in place
with sandbags or radiolucent tape. (B542.1.w1)
- Ventrodorsal view - Place the rabbit in dorsal
recumbency on the cassette. Gently extend the thoracic limbs
cranially and the pelvic limbs caudally, securing them e.g.
with tape. (B542.1.w1)
- Head:
- Lateral view - place the rabbit in right
lateral recumbency with its head on the cassette. Place a foam
wedge under the rostal part of the head to bring the sagittal
plane of the head parallel with the table; if necessary, use
radiolucent tape to maintain the head position. Keep the
rabbit's body in a straight lateral posture and have the legs
positioned symmetrically. (B542.1.w1)
- Dorsoventral view - Place the rabbit in ventral
recumbency, mandible resting on the casette. Extend the
thoracic limbs cranially and laterally at about a 45-degree
angle to the long axis of the body. (B542.1.w1)
Views
- Standard practice is to take two views, 90 degrees apart, of the
part of the animal which is of interest, generally a lateral and a
dorsoventral or ventrodorsal view.
(B601.5.w5, B602.37.w37,
B604.3.w3)
- Taking both right and left lateral views can improve assessment
of unilateral lesions. (J29.10.w1)
- Thorax:
- Exposing the radiograph when the patient is at maximum
inspiration (natural, if this point can be seen, or by use of
positive pressure ventilation in an intubated rabbit), enhances
evaluation of the lung fields. (B542.1.w1,
J29.10.w1)
- Standard views are lateral plus dorsoventral. (B339.1.w1)
- For the lateral view, centre the x-ray beam on the caudal
border of the scapulae (thoracic limbs extended forwards), with
the field of the x-ray beam including both the caudal neck and the
cranial abdomen. (B542.1.w1)
- Maximum information is obtained by taking both left and right
lateral views. (J29.10.w1)
- For the dorsoventral view, centre the x-ray beam on the
middle of the thoracic spine, in the midline, with the field of
the x-ray beam including the caudal neck and the cranial abdomen.
(B542.1.w1)
- Abdomen:
- Lateral and ventrodorsal views are usually taken; sometimes a
dorsoventral view is taken in addition to the lateral view. (B339.1.w1,
J29.10.w1)
- For the lateral view, centre the x-ray beam in the
mid-abdomen, with the field of the x-ray beam extending to include
the caudal thorax and the whole of the pelvis. (B542.1.w1)
- For the ventrodorsal view, centre the x-ray beam on the
middle portion of the lumbar spine, in the midline, with the field
of the x-ray beam including the caudal thorax and the whole of the
pelvis. (B542.1.w1)
- Expose when the rabbit is at end expiration. (B542.1.w1)
- Head
- For separate views of the dental arcades, oblique views are
needed.
(B601.5.w5, B602.37.w37,
B601.5.w5)
- For the lateral view, centre the x-ray beam just rostral
and ventral to the eye, with the field of the beam extending to
the cervical region. (B542.1.w1)
- For the dorsoventral view, centre the x-ray beam on the
midline directly between the eyes; a for the lateral view, the
field of the beam should include the cervical vertebrae. (B542.1.w1)
- A rostrocaudal view of the head is useful for visualising the
frontal sinuses or the temporomandibular joints.
(B601.5.w5)
- Note: Right and left oblique views (which separate the
dental arcades), in addition to lateral and ventrodorsal views,
provide optimum information; all four views can be obtained
on a single small x-ray plate. (V.w125)
- Limbs:
- Mediolateral views plus dorsopalmar (for the
front legs) or dorsoplantar (for the hind legs) views. (B339.1.w1,
B604.3.w3)
Equipment
Radiography unit and settings
- Because of their rapid respiratory rate, short exposure times (less
than 1/60th of a second) are needed. (B604.3.w3)
- A radiographic machine capable of
producing 40 - 70 kV, 300 mA and exposure times of 0.008 - 0.16 s (i.e. down
to 1/120 s) is recommended.
(B601.5.w5, J29.10.w1,
J34.23.w2)
- For thoracic and abdominal radiographs, kVp 45 - 60, 2 - 6 mAs
and a 1/30 to 1/120th second exposure time is suggested. (B604.3.w3)
- The higher end of the kVp is used where bone is thick or
superimposed (e.g. radiography of the skull). (J29.10.w1)
- A range of 40 - 100 kV, 5.0 - 7.5 mAs and rapid exposure times
(down to 0.017 of a second and faster) is suggested. (B542.1.w1)
- A tube stand allowing 90 degree rotation for horizontal beam
radiography is useful. (B602.37.w37)
- Equipment which allows alteration of the focal-film distance is
useful. (J34.23.w2)
- Usually the focal-film distance used in about 90 cm. (B604.3.w3)
- For enlarged radiographs, the focal-film distance is reduced to
80 cm with a focal size of 0 - 15 mm. (J29.10.w1)
- Human dental radiograph machines can be useful for fine detail views
of the head and distal limbs. However, these machines, which usually
have a fixed voltage and amperage, may require longer exposure times
(0.1 - 3.0 s) so that chemical restraint is essential.
(B601.5.w5)
- Preferably use a beam-limiting device. (B604.3.w3)
Film and cassettes
- Rabbits have low soft tissue density; it is useful if contrast can
be enhanced. (B604.3.w3)
- Generally no grid is needed for these small animals.
(B601.5.w5, B602.37.w37)
- A grid is necessary for larger rabbit breeds where the body
thickness is likely to exceed 10 cm.
(B601.5.w5, B602.37.w37)
- Fast, high-resolution, high detail rare earth intensifying screens should be
used. (B604.3.w3)
- For imaging the distal limbs as well as for dental imaging,
non-screen dental film is useful.
(B601.5.w5)
- These films are available in small sizes, ideal for intra-oral
views.
(B601.5.w5, J29.10.w1)
- Non-screen mammography film is useful for enhancement of both soft
tissue and distal limb detail.
(B601.5.w5, J29.10.w1);
single-intensifying screen cassettes and single-emulsion mammography
film is also useful. (B602.37.w37)
Contrast media
- Liquid barium sulphate, 10 - 15 mL by mouth or via an orogastric
tube can be useful for an upper GIT contrast study. (B602.37.w37)
- This is useful for demonstrating a gastric hairball (B604.3.w3)
which is often present in cases of gastric stasis.
- Iohexol (Omnipaque) can be used instead if there is a suspicion of
gastrointestinal perforation. (B602.37.w37)
- For excretory urogram:
- Iothalamate sodium or meglumine at 2 mL/kg intravenously. (B602.37.w37)
- Meglumine can also be administered into the bladder via a
urinary catheter for cystography; if the bladder is distended
until it is palpably turgid, filing defects etc. are visible. (B602.37.w37)
- Iodine-based contrast medium for myelography and urinary contrast
studies. (B601.5.w5,
P3.2005a.w1)
Radiographic Interpretation
"The most important requirements for radiographic interpretation
are a firm appreciation of normal anatomy and an awareness of the patterns
of radiographic change in response to disease processes." (J34.23.w2)
- Interpretation follows the same principles as for other species. (B602.37.w37)
- Note any changes in the size, shape, number, location, margins and
opacity of body parts on each view. (B602.37.w37)
- Interpret in conjunction with the known anatomy and variations, (B602.37.w37)
and in the light of clinical
signs. (J29.10.w1)
- Experience is needed for accurate interpretation. (B604.3.w3)
Thoracic cavity
For assessment of the heart, lungs and mediastinum.
- On lateral view, "The thorax is short cranio-caudally and
the heart lies well forward and in an upright position. The diaphragm
is long and sloping. The trachea runs dorsally almost parallel with
the thoracic vertebrae and its cartilage rings are usually well
mineralized." The cairina is at about the 4th or 5th
intercostal space. The aorta is generally not visible; the caudal vena
cava may be visible. (J8.22.w1)
- On the ventro-dorsal or dorso-ventral view, the cardiac silhouette
is approximately triangular and relatively large. Much of the dorsal
diaphragmatic lung field is covered by the liver density. The aortic
arch may be visible (overlying the left side of the hear. The scapulae
may overlie the caudal lung fields. J8.22.w1)
- Rabbits have a small thoracic cavity relative to their body size.
Radiographically, this means that the heart appears abnormally large
and occupies most of the cranioventral part of the thoracic cavity.
Additionally, the front legs are superimposed on the cranial thorax,
obscuring detail. It can be difficult to interpret thoracic
radiographs. (B339.1.w1,
B601.5.w5, B601.7.w7, J34.23.w2)
- The heart, trachea, aorta, vena cava and caudal lung lobes should be
visible. (J513.6.w5)
- The thymus obscures the cranial lung lobes and the cranial
border of the heart. (J513.6.w5)
- The heart is normally found between the fourth and sixth ribs. (B601.5.w5)
- In overweight rabbits, the heart shadow may be larger than usual
due to pericardial fat deposits. (B339.1.w1,
B601.5.w5)
- Pericardial and plural effusion may be imaged in a rabbit with
cardiac disease. (J513.6.w5)
- The heart can be enlarged with cardiomyopathy or valvular
disease. (B601.5.w5)
- Major blood vessels (e.g. aorta, subclavian arteries) may have increased density in: (B601.5.w5,
J513.6.w5)
- The heart may be displaced caudally with thymic neoplasia; the
thymus will also be visible as a precardiac shadow. (B601.5.w5)
- The lungs are small, particularly the cranial lobes. (B601.7.w7)
- Radiographic abnormalities include: (B601.5.w5)
- Consolidation of one or more lobes due to chronic infection or
abscess. (B601.5.w5)
- Note: indistinct radiographic contours may be due to
subcutaneous and pericardial fat rather than lung
consolidation. (J34.23.w2)
- Parenchymal masses such as metastases from neoplasia elsewhere in the body (e.g.
Endometrial Adenocarcinoma and other Uterine Neoplasia in Lagomorphs). (B601.5.w5,
B601.7.w7, J29.10.w1, J513.6.w5)
- Pleural effusion - caudal lung border rounded, pleural space
widened on dorsoventral view. (B601.5.w5,
B601.7.w7)
- Empyema - on lateral views, ventrally in the thorax, homogenous
increased density obscuring the cardiac silhouette. Trachea in a
normal position. On dorso-ventral views, homogenous increased
density and cardiac shadow obscured, with the trachea displaced to
one side in unilateral cases while in bilateral cases fluid
density was visible between the lung lobes (collapsed) and the
thoracic wall. With large amounts of pus, the diaphragm wa
displaced caudally and the ribs were spread wider than usual. (J8.22.w1)
- Possibly air alveolograms and air bronchograms in early lung
infection. (B601.5.w5)
Abdominal cavity
- The abdominal cavity is relatively large. (B601.5.w5)
- Large amounts of retroperitoneal and abdominal fat may displace the
abdominal contents ventrally. (J34.23.w2)
- The liver, kidneys, stomach, intestines and bladder should be
visible; the spleen is not visible. (J513.6.w5)
- Large amounts of gas in the GIT indicates reduced motility. (J513.6.w5)
- The liver is in the cranial abdomen, flattened, cranial to
the stomach, and is normally under the
caudal ribcage. (B339.1.w1,
B601.5.w5, J8.23.w1)
- The stomach
- Normally lies mainly within the costal arch. (J8.23.w1)
- Should always contain food and may have a small gas cap (normal). (B601.5.w5)
- Appears as mottled soft-tissue density plus gas. (J8.23.w1)
- Ventro-dorsal view: antrum, on the right, is considerably
cranial to the fundus which is on the left. (J8.23.w1)
- Large amounts of gas are abnormal. (B601.5.w5)
The stomach may contain only fluid and gas, or be empty, with
intestinal impaction. (J8.23.w1)
- With gastric stasis, the stomach may be full of gas and ingesta/trichobezoars
and is large; it may project caudal to the margin of the ribcage. (B339.1.w1,
B600.10.w10,
B601.5.w5, B602.16.w16,
J8.23.w1, J60.8.2)
- The typical trichobezoar is a soft tissue density,
ill-defined with a rim of gas outlining it. J34.23.w2
- May contain visible lead in rabbits with Lead Poisoning.
(J29.10.w1)
- The small intestines
- These are displaced dorsally and to the left in the abdomen by
the caecum. (J34.23.w2)
- Segments of small bowel containing gas may be distinguished from
large bowel by their curvilinear radioluscent configuration. (J8.23.w1)
- These may be full of gas for example with Mucoid Enteropathy.
(B600.10.w10)
- If the stomach and small intestines, but not the large
intestines, are severely distended, obstruction should be
suspected. (J34.23.w2)
- Complete obstruction or radiodense foreign bodies may be visible
on plain radiographs. (J29.10.w1)
- Contrast studies may show partial obstructions, lesions, and the
position of the small intestines. (J29.10.w1)
- The large intestines and caecum take up a large percentage of
the abdomen; the contents are of mottled radiographic density. (B339.1.w1,
B601.5.w5, J8.23.w1,
J29.10.w1)
- The caecum
- Is ventral and mainly on the right side of the abdomen. (B339.1.w1,
B601.5.w5)
- It is generally large and fluid-filled. (B604.3.w3);
it should always be filled with ingesta. (B339.1.w1,
B601.5.w5)
- Small amounts of gas may be present in the normal caecum. (B339.1.w1,
B601.5.w5)
- Excessive gas and fluid suggests colic and ileus. (B601.5.w5)
Some sections of intestines may be distended with gas and others
filled with ingesta. (J8.23.w1)
- The large bowel may be empty and distended with gas in gastric
impaction (while the stomach contains large amounts of dense
material). (J8.23.w10
- With Mucoid
Enteropathy in Rabbits
the whole caecum and large intestines may be full of fluid and
gas. (B601.5.w5)
- With Mucoid
Enteropathy in Rabbits, typically the small intestines are
full of gas, the stomach is full, the colon is grossly distended
with mucus and the contents of the caucum are dense and
dehydrated. (J513.6.w5)
- With Caecal Impaction a sausage-shaped
mass is visible in the ventral abdomen (B600.10.w10);
the colon is relatively empty and the small intestines are often
mildly or moderately distended with gas. (J34.23.w2)
- The descending colon and rectum contain faecal pellets. (B601.5.w5,
J8.23.w1) these
are generally but not always visible. (J8.23.w1)
- The kidneys are generally easy to see outlined by the
retroperitoneal (sublumbar) fat pads.
- A 1982 study noted that the left kidney was usually visible on
both lateral and ventro-dorsal views, while the right kidney was
only seen in about half of 27 normal rabbits, and was more easily
seen in the lateral view. (J8.23.w1)
- The right kidney is at about T13/L1 with the left kidney more
caudal, about L3 - L5. (J8.23.w1)
- Each kidney should measure about 1.8 (range 1.4 - 2.2) times the
length of the second lumbar vertebra. (B601.5.w5);
1.25 -1.75 times he
length of the second lumbar vertebra. (J8.23.w1)
- Common abnormal findings are renal and/or ureteral calculi (Urolithiasis in Lagomorphs). (B601.5.w5)
- Note: the kidneys are often pushed ventrally by the large
retroperitoneal (sublumbar) fat pads in pet rabbits. (B339.1.w1)
- The bladder normally contains calcium carbonate crystals
which assist in visualisation of the bladder as a radiodense structure
on plain radiographs. (B339.1.w1,
B601.5.w5)
- The bladder itself is not generally visible, but the urine
within it is generally visible as a homogenous soft tissue
density, ventral to the colon in the caudal abdomen. (J8.23.w1)
- Excessive amounts of calcium sludge results in an intense
bladder outline. (B601.5.w5)
- Uroliths in rabbits are usually composed mainly of calcium and
are radiodense; therefore large uroliths (calculi) may be clearly
visible on a plain radiograph (Urolithiasis in Lagomorphs). (B601.5.w5,
J29.10.w1, J34.24.w3,
J513.6.w1)
- There may be radio-opaque urolith "sand" in the
dependent part of the bladder; in an extreme case the whole
bladder may be distended and radio-opaque, and may displace other
abdominal organs cranially. (J4.217.w4)
- Note: it is important that the radiograph covers the whole pelvis if
urethral calculi are to be detected. (J513.6.w1)
- The uterus may be enlarged associated with pregnancy,
neoplasia (particularly adenocarcinoma - Uterine Neoplasia in Rabbits),
Endometrial Hyperplasia - Uterine Polyps in Rabbits
or pyometra (Uterine Infection in Lagomorphs).
(J8.23.w1)
- "Multiple large locular masses" in the
caudoventral abdomen, with craniodorsal displacement of the
intestines, may be seen with pyometra. These can be very large and
take up a large part of the abdomen. (J8.23.w1)
- Mummified fetuses (both intra- and extra-uterus) have been detected
radiographically as fetal skeletal remnants, sometimes in abnormal
configurations, in the caudo-ventral abdomen. (J8.23.w1,
J495.32.w5)
- Fetal malpresentation may also be seen (e.g. transverse
presentation). (J8.23.w1)
- The abdominal aorta and iliac arteries may be visible if
calcified (Soft Tissue Mineralization - Kidney Calcification in Rabbits).
(J29.10.w1)
- In parous does, the nipples can be seen - on ventro-dorsal
views these appear as small circular densities superimposed over the
abdominal contents, while in lateral views they are seen along the
ventral body wall. (J8.23.w1)
- Abdominal abscesses may be visible on radiography and may
have diffuse calcification; occasionally a calcified abscess may be
visible radiographically (circumscribed calcified mass) but not
causing any clinical signs. (J8.23.w1)
- Free fluid in the distended abdomen may be visible
radiographically and should be sampled by abdominocentesis (Abdominocentesis and Diagnostic Peritoneal Lavage in Rabbits).
Transudate
is present with heart failure (cardiomegally also seen). (J8.23.w1)
- Contrast medium:
- Gastro-intestinal
- An air gastrogram may be useful to highlight trichobezoars.
(B339.1.w1)
- 10 - 15 mL of positive contrast medium (barium sulphate) given by orogastric or
nasogastric tube, may be used to outline the gastric contents (B601.5.w5)
and may be useful in detection of gastro-intestinal foreign body,
although the presence of gas, and
recirculation of barium by caecotrophy, may make interpretation
problematic. (B602.16.w16)
- Take films at time zero and then every 20 minutes. (B339.1.w1)
- One study found that with a liquid marker, 32% reached the
caecum within an hour and 80% reached it within 12 hours.
- Urinary
- Negative contrast (5 - 8 mL/kg air injected into the bladder
through a 3.0 - 3.5 French urinary catheter). can be used to
outline the lining of the bladder. (B601.5.w5)
- Use of carbon dioxide rather than air removes the risk
of an iatrogenic air embolism. (B542.1.w1)
- Adding 2.0 - 3.0 mL of an iodine-based contrast medium
allows double-contrast radiographs. (B601.5.w5)
- Double-contrast studies are particularly useful in
rabbits with large amounts of radiopaque material in the
bladder. (B542.1.w1)
- Note: if, at the end of the study, the bladder is
prominently distended, use the catheter to withdraw urine
and contrast media. (B542.1.w1)
- An excretory urogram (Intravenous pyelography) can
be carried out by injection of 1- 2 mL/kg iodine-based contrast
medium intravenously, for evaluation of renal function
in rabbits with renal calculi. (B339.1.w1,
B601.5.w5,
B602.18.w18, J513.6.w1)
Head
- Normal rabbits with a wild-type head have a relatively elongated
skull, six cheek teeth in the upper arcade and five in the lower
arcade, four main incisors (two maxillary and two mandibular) and two
peg teeth behind the main maxillary incisors.
- There are no canines and there is a considerable diastema (gap)
between the incisors and the cheek teeth. (B601.5.w5)
- At rest, the cheek teeth should not be in contact; there should
be a zig-zag occlusal surface on each dental arcade. (B601.5.w5)
- The lower incisors should meet with the groove between the main
upper incisors and the peg teeth. (B601.5.w5)
- Brachycephalic rabbits are commonly seen. (B601.5.w5)
- Mandibular prognaithism is commonly seen. (B601.5.w5)
- Overall skull length is
reduced and length of the maxillary diastema is reduced, while
mandibular length is normal. (B614.13.w13)
- The rabbit has quite large rostral nasal passages, in which are fine
trabeculae which may be visible on a lateral radiograph. (B601.5.w5)
- To view the nasal passages on a dorsoventral view, use small
dental non-screen film placed inside the mouth. (B601.5.w5)
- On lateral view, "The cranial cavity is not clearly
delineated. The frontal sinuses are small and the frontal bones
overlying them are often slightly roughened. The nasal bone forms a
marked spicular prominence." (J8.22.w1)
- On ventro-dorsal view, "The cranial cavity is small and its
margins are indistinct. The zygomatic arches are flat and have
prominent bony projections at their rostral ends." (J8.22.w1)
- Radiography is an essential tool in the assessment of rabbit dental
disease. (B601.18.w18)
- Assess: (B601.18.w18)
- Length of the supragingival crown in the incisors and the cheek
teeth.
- Positions of the apices of the teeth.
- Occlusal surfaces of the cheek teeth.
- Condition of alveolar bone.
- Whether the palatine shelf and the dorsal border of the mandible
slightly converge rostrally (normal).
- Abnormalities which may be visible include: (B601.5.w5,
B601.18.w18, J8.22.w1,
J29.10.w1,
J513.6.w6)
- Malocclusion of the incisors;
- Abscess formation with bone lysis, and proliferation of new bone
around the abscess;
- Periodontal disease;
- Lysis of alveolar bone;
- Ankylosis - blurring of the boundaries between the alveolus and
the tooth.
- Dental arcades (cheek teeth) touching one another at rest;
- Palatine shelf and the dorsal border of the mandible parallel
(due to excessive length of the cheek tooth crowns forcing the
mandible away from the maxilla).
- Elongation of tooth roots;
- In the maxilla, tooth roots may extend into the nasal
passages and the orbit.
- In the mandible, tooth roots may distort the ventral surface
of the mandible.
- "Wave mouth" - occlusal surface between the dental
arcades irregular and uneven.
- Cheek teeth grossly irregular;
- Pathological fractures of the mandible.
- Fractures generally occur in the thin caudal section of the
mandubular ramus. (J513.6.w6)
- Assessment of the bony structures of the middle ears:
- A dorsoventral view is most informative; it is important to have
accurate alignment. (B600.12.w12,
B601.5.w5)
- The bullae are well developed, with relatively thicker bone than
in cats and dogs, and are easily distinguished particularly in
ventro-dorsal views. (J8.22.w1)
- Bone sclerosis and loss of fine trabecular bone structure may be
seen. (B601.5.w5,
J29.10.w1)
- With a unilateral disease process, the bone of one tympanic
bulla may be obviously thickened and proliferative compared to the
normal bulla on the other side. (J513.6.w6)
- Note: radiographic changes in the bullae are not always
easily correlated with clinical signs. (J513.6.w6)
- Other abnormalities which may be seen include traumatic jaw
injuries and skull neoplasia. (B601.5.w5,
B601.18.w18)
- Contrast studies are useful for assessment of the
nasolacrimal duct in Dacrocystitis in Rabbits
- Iodine-based contrast medium, 0.5 - 1.0 mL (B339.1.w1)
is injected into the punctum lacrimale - the single nasolacrimal ostium which is deep
in the craniomedial portion of the lower conjunctival sac. (B528.14.w14,
B600.11.w11, B601.5.w5,
J34.24.w3)
- Take films (lateral or oblique lateral) immediately after
injecting the contrast medium. (B339.1.w1)
- With blockage of the duct, the contrast material remains in
the portion of the duct, often dilated, caudal to the
blockage, and does not pass through to the nasal cavity.
- A dilute preparation (e.g. sodium/meglumine iothalamate,
Conray 280) is cheap and easy to inject into the duct.
- A concentrated solution is harder to inject but provides a
clearer image, and for a longer period of time.
- A good image of the duct is harder to achieve if the duct is
normal since it passes through to the nose where it may be
inhaled into the nasal passages, resulting in superimposition
on the radiographic film.
(B600.11.w11)
- An oblique lateral view allows assessment of both nasolacrimal
ducts, avoiding superimposition. (B601.5.w5)
Axial and appendicular skeleton
- The skeleton is relatively delicate (6 - 7% of total body mass).
Rabbits have a hamate process and a hooked suprahamate process on the
scapula; they also possess small clavicles. (B339.1.w1)
- Radiography is essential in the investigation of paresis or
paralysis. (B600.12.w12,
J513.6.w6)
- Radiography of the spine allows detection of fractures, luxations or
subluxations and spondylosis, as well as spinal abnormalities such as
scoliosis or hemivertebrae. (B600.12.w12,
B601.5.w5, B601.11.w11,
B602.20.w20, J15.28.w1,
J245.24.w1, J513.6.w6)
- Radiography allows assessment of skeletal mineralisation and
detection of osteopaenia and osteosclerosis. (B600.12.w12)
- Radiographic assessment of the limbs is useful in the diagnosis and
assessment of: (B601.5.w5,
J29.10.w1, J513.6.w6)
- Myelography
- This is extremely valuable for the detection of Intervertebral Disc Disease in Rabbits,
spinal abscesses and spinal tumours. (B601.5.w5,
N12.38.w1)
- Myelography is usually performed via the L5 - L6 or L6 - L7 intervertebral
space, but can also be performed via the cisterna magna. (J29.16.w7,
P3.2005a.w1)
- If contrast is injected at the lumbar site:
- 0.4 mL of iodine-based contrast medium, injected via a 23 G, 30 mm (1
1/4 inch) needle (for an average 2.5 kg rabbit) generally will provide contrast from T2 to L7
and demonstrate lumbar spinal lesions within a few minutes. (P3.2005a.w1)
- This site is generally preferred for myelography, since most
lesions are in the lumbar area. (J29.16.w7)
- 1.0 - 3.0 mL (depending on the rabbit's size) iohexol (300
mg iodine per mL, Omnipaque, GE Healthcare, Buckinghamshire,
UK) can be injected. (J29.16.w7)
- If contrast is injected at the atlanto-occipital junction (cisterna
magna): (J29.16.w7)
- Inject contrast agent (e.g. 1.0 - 3.0 mL (depending on the
rabbit's size) iohexol (300 mg iodine per mL, Omnipaque, GE
Healthcare, Buckinghamshire, UK), then withdraw the
needle.
- Place the rabbit in lateral recumbency with its head
elevated above its body; this allows gravity to assist
movement of contrast agent caudally.
- Periodically turn the rabbit over onto the other side so
that the contrast agent is not in contact with one side rather
than the other for too long.
- Take lateral and dorso-ventral radiographs as the contrast
medium moves caudally.
- Note: compared with lumbar injection of contrast, a
longer time is needed for the medium to reach the lumbar area
where lesions are most commonly found, and the contrast medium
will be diluted more, which may give poorer imaging.
(J29.16.w7)
- Note:
- Rabbits often appear weak and slightly sore in the hours
immediately after myelography, probably due to the spinal
manipulation associated with the procedure. Analgesics
should be given to rabbits undergoing myelography. (J29.16.w7)
- Seizures can occur post-myelography. Control with diazepam
and provide supportive care. (J29.16.w7)
See: Epilepsy and Convulsions in Bears and Lagomorphs
- Paralysis can occu post-myelography; in a reprted case,
resolution of the condition occurred within two days. (J29.16.w7)
Other uses of radiography
Radiography is also used for:
- Checking correct placement of a nasogastric tube or oesophagostomy
tube. (B601.2.w2,
J29.15.w2)
- Confirming adequate alignment of fractures after reduction and
placement of implants, and monitoring fracture repair. (B601.17.w17,
B606.10.w10, P112.1993.w1)
Records
- For wild lagomorphs, keep records of the species, age, weight,
region examined, radiographic techniques used and radiograph quality;
this will assist in developing the best techniques for future
examinations. (J213.9.w4)
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