Page 282 - Small Animal Internal Medicine, 6th Edition

254 PART II Respiratory System Disorders

NASAL SWAB PINCH BIOPSY
The least traumatic techniques are the nasal swab and nasal Pinch biopsy is the author’s preferred method of nasal biopsy.
VetBooks.ir flush. Unlike the other collection techniques, nasal swabs can In the pinch biopsy technique, alligator cup biopsy forceps
(minimum size, 2 × 3 mm) are used to obtain pieces of nasal
be collected from an awake animal. Nasal swabs are useful
for identifying cryptococcal organisms cytologically and
tissue specimens can be obtained, and guided specimen col-
should be collected early in the evaluation of cats with mucosa for histologic evaluation (Fig. 14.14). Full-thickness
chronic rhinitis. Other findings are generally nonspecific. lection is more easily performed with this technique than
Exudate immediately within the external nares or draining with previously described methods. When possible, the
from the nares is collected using a cotton-tipped swab. Rela- biopsy forceps are passed adjacent to a rigid endoscope and
tively small swabs are available that can facilitate specimen directed to any gross lesions. If a flexible scope is used,
collection from cats with minimal discharge. The swab is biopsy instruments can be passed through the biopsy channel
then rolled on a microscope slide. Routine cytologic stains of the endoscope. The resulting specimens are extremely
are generally used, although India ink can be applied to small and may not be of sufficient quality for diagnostic
reveal cryptococcal organisms (see Chapter 97). purposes. Larger alligator forceps are preferred. If lesions are
not present grossly but are present radiographically or by CT,
NASAL FLUSH the biopsy instrument can be guided using the relationship
Nasal flush is a minimally invasive technique. A soft cath- of the lesion to the upper teeth.
eter is positioned in the caudal region of the nasal cavity After the first piece is taken, bleeding will prevent further
via the oral cavity and internal nares, with the tip of the visual guidance; therefore the forceps are passed blindly to
catheter pointing rostrally. With the animal in sternal the position identified during rhinoscopic examination (e.g.,
recumbency and the nose pointed toward the floor, approxi- meatus involved and depth from external naris). If a mass is
mately 100 mL of sterile saline solution is forcibly injected present, the forceps are passed in a closed position until just
in pulses by syringe. The fluid exiting the external nares before the mass is reached. The forceps are then opened and
is collected in a bowl and can be examined cytologically. passed a short distance farther until resistance is felt. Larger
Occasionally nasal mites can be identified in nasal flush- forceps, such as a mare uterine biopsy instrument, are useful
ings. Magnification or placement of dark paper behind for collecting large volumes of tissue from medium-sized to
the specimen for contrast may be needed to visualize the large dogs with nasal masses. No forceps should ever be passed
mites. A portion of fluid can also be filtered through a into the nasal cavity deeper than the level of the medial canthus
gauze sponge. Large particles trapped in the sponge can be of the eye without visual guidance to keep from penetrating
retrieved and submitted for histopathologic analysis. These the cribriform plate.
specimens are often insufficient for providing a definitive A minimum of six tissue specimens (using 2 × 3-mm
diagnosis. forceps or larger) should be obtained from any lesion. If no

FIG 14.14
Cup biopsy forceps are available in different sizes. To obtain sufficient tissue, a minimum
size of 2 × 3 mm is recommended. The larger forceps are particularly useful for obtaining
biopsy specimens from nasal masses in dogs.