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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.
- It is essential that the patient is immobile while the radiograph is
taken. (J29.10.w1)
- Usually, positioning used is similar to that used for cats and dogs. (J29.10.w1)
- Generally, chemical immobilisation is required.
(J15.24.w5, J29.10.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)
- Endotracheal intubation is preferable if a lengthy sequence of
radiographs is to be taken.
(B602.37.w37)
- For details of appropriate chemical restraint, see: Treatment and Care
- Anaesthesia and Chemical Restraint
- Required positioning can be achieved in the anaesthetised ferret using sandbags, radiolucent tape and foam wedges. (J15.24.w5,
B542.1.w1)
- Thorax:
- Lateral view - place the patient 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 patient 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 ferret 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 ferret 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 ferret 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
ferret's body in a straight lateral posture and have the legs
positioned symmetrically. (B542.1.w1)
- Dorsoventral view - Place the ferret 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.
(B602.37.w37)
- Taking both right and left lateral views can improve assessment
of unilateral lesions. (J29.10.w1)
- Thorax:
- Standard views are lateral plus ventrodorsal; maximum
information is obtained by taking both left lateral and right
lateral views in addition to the ventrodorsal view. (J29.10.w1)
- 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 ferret), enhances
evaluation of the lung fields. (J29.10.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)
- The field must include the thoracic inlet cranially and the last
rib caudally if the entire lung field is to be covered. (J15.24.w5)
- 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:
- Radiographs may provide information on the liver,
gastrointestinal tract, spleen, kidneys and urogenital tract.
- Lateral and ventrodorsal views are usually taken. (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)
Centre the beam between the last rib and the wing of the ileum,
with the ferret's legs extended caudally. (J15.24.w5)
- 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 ferret is at end expiration. (B542.1.w1)
- Head
- For the skull, standard views are lateral and dorsoventral;
sometimes a rostrocaudal view is taken also. (BJ29.10.w1)
- The dorsoventral view allows the tympanic bullae to be seen.
(J29.10.w1)
- Oblique views may be used for examination of particular
areas. (J29.10.w1)
- The rostrocaudal view is useful for imaging the frontal
sinuses and the temporomandibular joint. (B631.19.w19)
- 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)
- Note: Right and left oblique views (which separate the
dental arcades) allow the dental arcades to be viewed separately.
(B631.19.w19)
- For assessment of periodontal disease, including confirming the
true length of the tooth root, bisecting angle radiographs are
useful. For this view, the X-ray beam is positioned at 90 degrees
to the axis of the tooth being examined and 90 degrees to the
radiographic film, avoiding distortion and allowing the alveolar
socket to be assessed properly. (B631.19.w19)
- Limbs:
- Mediolateral views plus dorsopalmar (for the
front legs) or dorsoplantar (for the hind legs) views. (B339.1.w1)
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.
(J29.10.w1,
J34.23.w2, B631.19.w19)
- The higher end of the kVp is used where bone is thick or
superimposed (e.g. radiography of the skull). (J29.10.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, allowing magnification (which is particularly useful with
smaller patients). (B631.19.w19,
J34.23.w2)
- For enlarged radiographs, the focal-film distance is reduced to
80 cm with a focal size of 0 - 15 mm. (J29.10.w1)
Film and cassettes
- Generally no grid is needed for these small animals.
(B602.37.w37)
- Non-screen dental film is available in small sizes, ideal for
dental, including intra-oral, views, and for imaging the distal limbs.
(B631.19.w19, J29.10.w1)
- Non-screen mammography film is useful for enhancement of both soft
tissue and distal limb detail.
(B631.19.w19, J29.10.w1);
single-intensifying screen cassettes and single-emulsion mammography
film is also useful. (B602.37.w37)
- Human dental radiographic units combined with non-screen dental film
can produce fine-detailed imaging. However, the exposure time may be
relatively long (e.g. 0.3 s) requiring chemical restraint of the
patient to avoid image blurring. (B631.19.w19)
Contrast media
- Contrast
- 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)
Thoracic cavity
For assessment of the heart, lungs and mediastinum.
- Ferrets have a rapid respiratory rate, therefore short exposure
times are preferred. (B631.19.w19)
- Heart
- This is placed further caudally than in the dog or cat. (B631.19.w19,
J15.24.w5)
The apex is to the left of the midline. (J15.24.w5)
- The relatively narrow thoracic cavity means that the heart may
look large and globe-shaped even when normal. (B631.19.w19)
- To evaluate the size of the heart, measure the long axis and the
short axis on a right lateral view, and measure the
distance from the start of the fifth to the end of the eighth
thoracic vertebrae, all in centimetres. Long axis (cm) plus short
axis (cm) divided by T5-T8 length. This should be 1.35 (+/- SD
0.07) for males, 1.34 (+/- 0.06) for females.
- Cardiac enlargement may occur with: (B631.19.w19)
- The heart may appear elevated from the sternum due to (normal)
fat deposition in the pericardial ligament; this must be
distinguished from pneumothorax. (B631.19.w19,
J15.24.w5)
- Lungs
- In pneumonia, usually an interstitial pattern is visible
initially, with an alveolar pattern as the disease progresses.
Marked bronchial patterns may be seen with severe disease. (B631.19.w19)
- Perihilar lung oedema may be visible with congestive heart
failure. (B631.19.w19)
- Pleural effusion may indicate:
- Calcification of soft tissues (lungs, major thoracic blood vessels,
also kidneys) may be incidental or indicate calcium/vitamin D3
oversupplementation. (B631.19.w19)
- Oesophagus
- In normal ferrets this is not easily visible. (B631.19.w19)
- Megaoesophagus in Ferrets
may be seen on plain lateral views. Contast studies make
visualisation easier.
- Barium sulphate, 10-15 mg/kg given orally; this may be mixed
with a palatable food such as a meat-mased enteric suport
formula, or e.g. strawberry-flavoured barium sulphate may be
accepted. (B631.19.w19,
B631.28.w28)
- Radiographs with barium may show an enlarged cervical and
thoracic oesophagus which may be as large as 2 cm in diameter. (B631.28.w28)
- Note: Anaesthesia can cause dilatation of the
oesophagus; this should be taken into consideration. (B627.11.w11)
- The condition of the mucosa can also be assessed. (B627.11.w11)
- Barium sulphate paste may be used to assess strictures and
motility of the oesophagus. (B631.19.w19)
- Fluoroscopy may also be useful in assessing the oesophagus. (B627.11.w11)
Abdominal cavity
This is elongated in shape. retroperitoneal fat deposits help to delineate
the organs clearly. (B631.19.w19)
- The liver
- The spleen
- This is normally relatively large (B631.19.w19)
Gross enlargement may occur with:
- The stomach
- On a dorsoventral view the stomach should be visible on the
left, with its cranial border at the level of T13; on the lateral
view, it should be just caudal to the dorsal part of the liver
shadow. No gas should be visible, except a small gas cap may be
seen in the fundus if a ferret has been starved prior to
anaesthesia. The pylorus should be just right of midling on the
dorsoventral view and the pyloric opening points craniodorsally. (B631.19.w19)
- Large quantities of gas are abnormal. (B631.19.w19)
See:
- The intestines
- The duodenal loop descends on the right side, close to the body
wall before curving cranially in the mid-abdomen, while the
jejunum is found further ventrally and in the mid-abdomen; on a
lateral view it is caudal and ventral to the stomach and should
contain ingesta and small gas bubbles. The ileum and large
intestine are not easily visible (the descending colon and rectum
are most easily seen) unless abnormal (e.g. filled with gas due to
obstruction).
- Complete obstruction or radiodense foreign bodies may be visible
on plain radiographs. (J29.10.w1)
- Radiolucent gastrointestinal foreign bodies often
presented with distended intestines and gas in the stomach. (B232.7.w7,
B602.3.1.w3A,
B627.11.w11,
B631.19.w19)
- Contrast studies may show partial obstructions, lesions, and the
position of the small intestines. (J29.10.w1)
- A contrast (barium) study will show any blockages caused by a
radiolucent foreign
body. (B232.19.w19,
B602.3.1.w3A,
B628.11.w11,
B631.25.w25)
- It may be possible to detect intestinal thickening, focal e.g.
with Lymphoma in Ferrets
or Proliferative Bowel Disease in Ferrets
or more diffuse e.g. with Inflammatory Bowel Disease in Ferrets
or Eosinophilic Gastroenteritis in Ferrets(B631.19.w19)
- The kidneys are generally easy to see outlined by the
retroperitoneal (sublumbar) fat pads. (B631.19.w19)
- The bladder
- Urolithiasis in Lagomorphs and Ferrets
is common, particularly in male ferrets, in which urinary
obstruction may occur when uroliths get lodged behind the os
penis. (B631.19.w19)
- Usually these are easily seen radiographically because they are
usually struvite (magnesium ammonium phosphate), although small
uroliths at the os penis may not be easily visible. (B631.19.w19)
- The uterus
- Pyometra in Ferrets
may be seen. (B631.19.w19)
- Fetuses may be detected in the last third of pregnancy, when
skeletal ossification has started. (B631.19.w19)
- Os penis this is J-shaped and can be seen radiographically in
male ferrets. (B631.19.w19)
- Contrast studies:
- Gastro-intestinal:
Before a contrast study the ferret should be faster for 3-4 hours,
reducing the contents of the intestinal tract. Longer periods of
fasting have been used but risk hypoglycaemia, particularly in
ferrets with Insulinoma in Ferrets.
(B631.19.w19)
- 10-15 mL/kg liquid barium sulphate may be given orally (Oral Medication and Syringe Feeding of Ferrets)
or by stomach tube. Strawberry-flavoured barium, or barium mixed
with a palatable liquid meat-based food may improve palatability.
(B631.19.w19)
- Take views at 5, 10, 20, 40, 60, 120 and 150 minutes. (B631.19.w19)
- Expect almost immediate emptying of the stomach, with a
total time for passage through the GIT of 75 +/-45 minutes in
a conscious ferret, but up to 130 +/-40 minutes in a ferret
sedated with ketamine plus diazepam. (B631.19.w19)
- If there is concern about a possible rupture or perforation
of the GIT, use a radio-opaque iodine-based product such as
iohexol, diluted 1:1 with tap water and given at 10-15 mL/kg.
(B602.37.w37,
B631.19.w19)
- Urinary
- Positive contrast studies can be used but uretheral
catheterisation can be challenging, even in the anaesthetised
ferret.
(B631.19.w19)
- If catheterisation can be achieved, iothalamate meglumine
and be injected and used for contrast; if the bladder is
expanded until turgid, this allows filling defects or abnormal
bladder location to be detected. (B602.37.w37)
- An intravenous pyelogram can be used to assess kidney size,
position and perfusion (and, after a delay, the bladder),
highlight renal and ureteral calculi and show cystic changes
and neoplasia. A non-ionic iodine containing medium such as
iohexol is used at 720 mg/kg given intravenously e.g. into the
cephalic vein (B631.19.w19)
(or iothalamate sodium or iothalamate meglumine, Conray,
Mallinckrodt Medical, St Louis, USA, at 2 mL/kg). (B602.37.w37)
- Non-ionic iodine is preferred, to avoid osmotic diuresis.
- The ferret should be properly hydrated before the
contrast medium is given.
(B631.19.w19)
Head
- Radiography of the head is commonly used in assessment of dental
disease, also in investigation of masses.
(B631.19.w19)
- The dental formula in the adult ferret is I 3/3, C1/1, P3/3,
M1/2.
(B631.19.w19)
- A bisecting angle radiograph (as described above) is useful in
assessing periodontal disease (Periodontal Disease in Rabbits and Ferrets).
(B631.19.w19)
- Tumours which may be seen (Neoplasia in Ferrets)
include osteomas, visible as increased irregularly shaped
areas growing from the surface of the normal bone of the skull or
mandible, and gingival squamous cell carcinoms seen as
radioluscent areas as they invade the underlying bone.
(B631.19.w19)
Axial and appendicular skeleton
- The skeleton is of an elongated shape with a small skull and
short limbs. There are vestigial clavicals and, in males, a J-shaped
os penis. The vertebral formula is C7, T15, L5 to 7, S3 and Cd 18.
Growth plates often close only when the ferret is about seven months
old, particularly for the long bones and pelvis. (B631.19.w19)
- Spinal lesions to be investigated include Intervertebral Disc Disease in Rabbits and Ferrets,
vertebral body fractures (Spinal Injury in Lagomorphs and Ferrets)
and neoplasia (Neoplasia in Ferrets),
particularly chordoma (usually of the tail but sometimes seen in the
cervical region) but also plasma cell myeloma, and lymphoma (Lymphoma in Ferrets).
(B631.19.w19)
- Traumatic injury to the long bones (Fractures in Ferrets)
or joints (Elbow Luxation in Rabbits and Ferrets)
may be seen. Osteomyelitis (post-traumatic or post-operative), as in
cats and dogs, is visible as lysis, malunion and periosteal
proliferation. (B631.19.w19)
- Various neoplastic lesions of the musculoskeletal system have been
described (Neoplasia in Ferrets).
(B631.19.w19)
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