Page 337 - Small Animal Internal Medicine, 6th Edition

CHAPTER 20 Diagnostic Tests for the Lower Respiratory Tract 309

complication of BAL in people, and increased airway resis­ cells from the larger airways, and fluid from later boluses is
tance has been documented in cats after bronchoscopy and more representative of the alveoli and interstitium.
VetBooks.ir BAL (Kirschvink et al., 2005). Albuterol in a metered dose Nucleated cell counts are performed on undiluted fluid using
BAL fluid is analyzed cytologically and microbiologically.
inhaler should be on hand to administer through the endo­
tracheal tube or by spacer and mask if needed.
differential cell counts and qualitative analysis using cyto­
After extubation the mucous membrane color, pulses, and a hemocytometer. Cells are concentrated onto slides for
the character of respirations are monitored closely. Crackles centrifugation or sedimentation techniques. Slides then are
can be heard for several hours after BAL and are not cause stained using routine cytologic procedures. Differential cell
for concern. Treatment with oxygen supplementation is con­ counts are performed by counting at least 200 nucleated
tinued by mask, oxygen cage, or nasal catheter if there are cells. Slides are scrutinized for evidence of macrophage acti­
any indications of hypoxemia. Oxygen supplementation is vation, lymphocyte reactivity, neutrophil degeneration, and
rarely necessary for longer than 10 to 15 minutes after BAL criteria of malignancy. All slides are examined thoroughly
in patients that were stable in room air before the proce­ for possible etiologic agents, such as fungi, protozoa, para­
dure; however, the ability to provide supplementation for an sites, and bacteria (see Figs. 20.12 and 20.15 to 20.17). As
hour or longer is a prerequisite for performance of this pro­ described for tracheal wash, visible strands of mucus can be
cedure, in case decompensation occurs. Considerations for examined for etiologic agents by squash preparation.
patients who continue to require oxygen supplementation or Approximately 5 mL of fluid is used for bacterial culture.
whose condition deteriorates include pneumothorax, result­ Additional fluid is submitted for fungal culture if mycotic
ing from rupture of a bulla or other cavitary lesion; aspira­ disease is among the differential diagnoses. Mycoplasma cul­
tion, as a complication of anesthesia; or cardiogenic edema tures or PCR are considered in cats and dogs with signs of
from fluid overload. bronchitis.

SPECIMEN HANDLING INTERPRETATION OF RESULTS
Successful BAL yields fluid that is grossly foamy, as a result Normal cytologic values for BAL fluid are inexact because of
of surfactant from the alveoli. Approximately 50% to 80% of inconsistency in the techniques used and variability among
the total volume of saline instilled is expected to be recov­ individual animals of the same species. In general, total
ered. Less will be obtained from dogs with tracheobroncho­ nucleated cell counts in normal animals are less than 400 to
malacia (collapsing airways). The fluid is placed on ice 500/µL. Differential cell counts from healthy dogs and cats
immediately after collection and is processed as soon as pos­ are listed in Table 20.3. Note that the provided values are
sible, with minimum manipulation to decrease cell lysis. For means from groups of healthy animals. Values from indi-
convenience, retrieved boluses can be combined for analysis; vidual patients should not be considered abnormal unless the
however, fluid from the first bolus usually contains more values are at least one or two standard deviations above these

TABLE 20.3
Mean (±Standard Deviation [SD] or Standard Error [SE]) of Differential Cell Counts From Bronchoalveolar
Lavage Fluid From Normal Animals a
BRONCHOSCOPIC BAL NONBRONCHOSCOPIC BAL
CELL TYPE CANINE (%)* FELINE (%) † CANINE (%) ‡ FELINE (%) §

Macrophages 70 ± 11 71 ± 10 81 ± 11 78 ± 15
Lymphocytes 7 ± 5 5 ± 3 2 ± 5 0.4 ± 0.6
Neutrophils 5 ± 5 7 ± 4 15 ± 12 5 ± 5
Eosinophils 6 ± 6 16 ± 7 2 ± 3 16 ± 14
Epithelial cells 1 ± 1 — — —
Mast cells 1 ± 1 — — —

a The provided values are means. Normal ranges can be expected to extend two standard deviations from the mean. See text for further
discussion.
*Mean ± SD, 6 clinically and histologically normal dogs. (From Kuehn NF: Canine bronchoalveolar lavage profile. Thesis for masters of
science degree, West Lafayette, Indiana, 1987, Purdue University.)
† Mean ± SE, 11 clinically normal cats. (From King RR et al.: Bronchoalveolar lavage cell populations in dogs and cats with eosinophilic
pneumonitis. In Proceedings of the Seventh Veterinary Respiratory Symposium, Chicago, 1988, Comparative Respiratory Society.)
‡ Mean ± SD, 9 clinically normal dogs. (From Hawkins EC et al.: Use of a modified stomach tube for bronchoalveolar lavage in dogs, J Am
Vet Med Assoc 215:1635, 1999.)
§ Mean ± SD, 34 specific pathogen–free cats. (From Hawkins EC et al.: Cytologic characterization of bronchoalveolar lavage fluid collected
through an endotracheal tube in cats, Am J Vet Res 55:795, 1994.)