Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

642 Small Animal Radiolo g y and Ultrasono graphy
The teeth should be examined carefully for evidence of tooth root abscess, and bones should
be examined for fractures. Absence of the fine trabecular pattern within the nasal cavity may
be caused by accumulation of fluid or soft tissue within the nasal cavity. The fluid may be
inflammatory or hemorrhagic, and the soft tissue may be associated with rhinitis or neoplasia.
Accumulation of fluid within the nasal cavity will cause some blurring of the normal parallel
pattern of the nasal conchae. 129 Loss of the larger bony turbinates usually indicates bone
destruction from tumor invasion or necrosis from fungal or chronic bacterial infection. Loss
of the turbinate pattern, especially in the ethmoid turbinates, is caused by destruction of the
conchae, which is most often associated with tumor or fungal rhinitis.
Rhinitis and Sinusitis. Rhinitis and sinusitis of bacterial origin may produce minimal,
marked, or no radiographic changes. The presence of a tissue density within the normally
air-filled nasal passages or paranasal sinuses may occur because of the presence of exudate
(Fig. 5-38). This density obscures the normally apparent fine bone pattern formed by the
turbinates. In many cases of rhinitis, the frontal sinuses also will contain exudate. This
increases their radiographic density from air to tissue dense. However, in dogs the lack of
frontal sinus involvement has been shown to have a relatively high positive predictive value
that the associated nasal disease is inflammatory rather than neoplastic. 130 In unilateral
nasal disease, comparison with the uninvolved side facilitates detection of increased opacity.
In bilateral disease, detecting increased opacity is more difficult. A triad of maladies
(sinusitis, situs inversus, and bronchiectasis) known as Kartagener’s syndrome has been
reported in the dog. 131,132 Rhinitis, pneumonia, and defective neutrophil function have
been reported in the Doberman. 133 When rhinitis is secondary to nonmetallic foreign
material in the nasal passages, the exudate usually obscures the outline of the foreign body.
Rhinitis may result from extension of infection around a tooth root, a periapical abscess,
into the nasal passages. 132 In this situation, the radiographic sign of a periapical abscess is
decreased density around the tooth root and will be evident in addition to the increased
nasal passage density. In many patients with bacterial rhinitis, the nasal turbinates appear
normal because the exudate drains to the outside and does not accumulate in the nasal cavity.
Obstruction to drainage will result in fluid accumulation within the nasal passages and
will obliterate some of the fine turbinate pattern. In chronic cases, destruction or obliteration
of the larger turbinates may be observed. Fungal rhinitis may present with radiographic
changes that are similar to those observed in association with bacterial rhinitis;
however, marked bone destruction with minimal exudate is more common, especially in
chronic cases. Destruction of the turbinates occurs and the vomer or nasal bones may be
destroyed partially or completely. The destroyed turbinate is not replaced with soft tissue,
resulting in a pattern that has been described as hyperlucent nasal passages (Fig. 5-39). 117
The presence of lucent foci in the nasal passage has been associated strongly with rhinitis
and not with neoplasia. 130 Bilateral destructive rhinitis, which does not destroy or deviate
the vomer, is more typical of fungal rhinitis than neoplasia.
Rhinitis and sinusitis of allergic or parasitic origin rarely produce radiographic
changes. Although turbinate destruction was reported in association with Capillaria sinusitis,
this amount of turbinate destruction is unusual. 66
Neoplasia. Tumors of the nasal passage most frequently appear as a soft-tissue density in
one or both nasal passages or frontal sinuses or both. Intranasal bone destruction, including
destruction of the vomer and nasal septum, may or may not be present. The tumor may
also extend through the maxilla into the retrobulbar space, externally resulting in a softtissue,
subcutaneous facial mass, or it may invade through the cribriform plate and result
in compression of the olfactory and frontal lobes of the brain. 115-117,124,134 This destruction
is the radiographic finding that has the highest positive predictive value for the diagnosis
of neoplasia. Occasionally new bone formation may be present within the nasal
cavity. A pattern of punctate, stippled, or globular calcification may be observed rarely in
nasal chondrosarcoma. However, because several tumor types occur in the nasal cavity and
most have no unique radiographic characteristic, it is only rarely possible to suggest a specific
cell type. 115-117,124,135 Deviation or destruction of the vomer with the presence of tissue
density in the nasal passages strongly suggests the presence of a neoplasm (Fig. 5-40).