Page 13 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery

Diagnostic imaging The other soft tissues of the neck (e.g. oesophagus, salivary
glands, thyroid and parathyroid glands) may be imaged with
Radiography
VetBooks.ir Radiography is of limited use in the evaluation of aural thyroid and parathyroid glands, the clinical utility is limited.
ultrasonography. However, apart from examination of the
In animals with disorders of the upper respiratory tract
disease. Radiographs may reveal ear canal stenosis and
calcification of the ear canal cartilage, when it is present.
graphy allows some information to be gained in the con-
The tympanic bulla may have a soft tissue opacity, indi- (e.g. laryngeal paralysis, tracheal collapse), ultrasono-
cating the presence of fluid or soft tissue. Bony prolifera- scious animal. This enables the clinician to be ready for
tion or erosion of the bulla may be present with otitis the likely diagnosis prior to anaesthesia.
media or if a tumour is present. However, the changes Ultrasonography is most useful for:
seen in the external canal may all be appreciated clinically
and, apart from documenting bony lysis or proliferation, • Evaluation of cardiac disease
radiography is insensitive in identifying the presence of • Examination of the pleural space in animals with a
otitis media, and it does not play a large part in decision- pleural effusion
making. However, substantial bone lysis, for instance of • Evaluation of a lung mass or mediastinal mass if a
the bulla, when dealing with aural neoplasia suggests that suitable acoustic window exists (e.g. the mass is in
a total ear canal ablation/lateral bulla osteotomy is unlikely contact with the chest wall, heart or diaphragm, or
to obtain a surgical margin. Therefore, if ear canal neo- there is a pleural effusion).
plasia is suspected, imaging of the skull, and the thorax,
is indicated. Advanced imaging
The pharynx and cervical trachea are suitable for radio-
graphic examination because of the presence of air within Computed tomography (CT) and magnetic resonance
imaging (MRI) are becoming more widely available and are
the lumina of these structures, giving a high contrast.
However, superimposition of other structures, particularly particularly useful for areas of complex anatomy because
the vertebral column, limits the examination to a lateral they eliminate superimposition. Although they generate
view. Lesions affecting the bony parts of the skull and images differently, they both produce a cross-sectional
neck (e.g. oral tumours) are good candidates for radio- tomographic image. These modalities are both suitable for
graphic evaluation. The remainder of the structures are examination of the head and neck. CT is more suited to the
generally soft tissue and in close proximity to each other assessment of bony lesions, particularly where destruction
with no contrasting substance (e.g. fat or air) between is present (e.g. middle ear), and for evaluation of the thorax
them, so the value of radiographic examination is limited to (Figure 1.1). MRI offers superior soft tissue differentiation
(e.g. soft tissue sarcoma) and is more appropriate for the
the identification of radiodense foreign material.
Radiography is an excellent tool for the evaluation of evaluation of the central nervous system (e.g. in animals
with central vestib ular syndrome). Both of these tech-
thoracic disease. Right and left lateral thoracic radio-
graphs should also be obtained if neoplasia is suspected. niques may be used for the evaluation of the nasal
passages and the sinuses, pharynx and larynx.
A standard lateral and dorsoventral (DV) or ventrodorsal
(VD) view are recommended for most conditions.
Scintigraphy
Contrast radiography: This imaging modality is not
Scintigraphy has relatively few indications in small animal
commonly used. The upper airways have inherent natural practice. It may be used for investigation of ectopic thyroid
contrast because of the air they contain, and contrast tissue in hyperthyroid cats and for a skeletal survey for
studies of the lower airways yield relatively little infor mation occult metastases from a malignant lesion (e.g. osteo-
for the potential hazard they represent. Ultrasonography of sarcoma of the rib).
the heart has largely replaced angiocardiography, and
direct visualization of the airways is more useful than a
contrast examination. The role of contrast radiography in
the evaluation of ear disease is minimal.
Three techniques may be of use, however:
• Sialography – may be used to identify the location of
leakage of saliva in a patient with a salivary mucocele
• Fistulography/sinusography – may be of use in
identifying the nature and extent of a cutaneous
draining tract and the connection with other structures
• Oesophagography – this is a valuable technique for the
evaluation of oesophageal disease. Its usefulness is
increased if real-time images are obtained with
fluoroscopy.

Ultrasonography
Ultrasonographic imaging complements radiographic imag-
ing as it allows an assessment of patients in which the
region of interest consists of areas of similar radiopacity in
close proximity (e.g. pleural effusion, neck mass); radio-
graphy is unable to differentiate between structures of Spiral computed tomography creates excellent images of the
similar radiopacity. Use of ultrasonography in the evaluation 1.1 pulmonary parenchyma. A hyperdense mass (m) is present in
of diseases of the ear, oral cavity and pharynx is limited. the periphery of the left lung.

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