Page 381 - Small Animal Internal Medicine, 6th Edition

CHAPTER 22 Disorders of the Pulmonary Parenchyma and Vasculature 353

pattern (see Fig. 20.8). In cats primary lung tumors often In animals with a large mass lesion, respiratory signs may
have a diffuse distribution by the time of presentation, and abate after excision, even if metastatic lesions are present
VetBooks.ir the radiographic pattern may be suggestive of bronchitis, throughout the lungs. If the lesions cannot be removed surgi-
cally, chemotherapy can be attempted (see Chapter 76). No
edema, or pneumonia.
Pulmonary neoplasia is occasionally associated with
lung tumors.
hemorrhage, edema, inflammation, infection, or airway protocol is uniformly effective for the treatment of primary
occlusion that can contribute to the formation of alveolar Metastatic neoplasms of the lungs are treated with che-
patterns and consolidation. Lymphadenopathy, pleural effu- motherapy. In most animals the initial protocol is deter-
sion, or pneumothorax can also be identified by radiography mined by the expected sensitivity of the primary tumor.
in some patients with neoplasia. Unfortunately, metastatic neoplasms do not always have the
Non-neoplastic disease, including fungal infection, lung same response to specific agents as the primary tumor.
parasites, aspiration of mineral oil, eosinophilic granuloma- Multicentric tumors are treated with standard chemo-
tosis, atypical bacterial infection, and inactive lesions from therapeutic protocols, regardless of whether the lungs are
previous disease, can produce similar radiographic abnor- involved. Multicentric tumors are discussed in Chapter 78.
malities. Pulmonary specimens must be evaluated to estab-
lish a diagnosis. Prognosis
Tracheal wash fluid cytology rarely results in a definitive The prognosis for animals with benign neoplasms is excel-
diagnosis. It is generally necessary to evaluate lung aspirates, lent, but these tumors are uncommon. The prognosis for
bronchoalveolar lavage fluid, or lung biopsy specimens. Mass animals with malignant neoplasia is potentially related to
lesions located adjacent to the body wall are readily sampled several variables, which include tumor histology, the pres-
by transthoracic lung aspiration. Accuracy and safety are ence of regional lymph node involvement, and the presence
improved with ultrasound guidance. Seeding of tumor as a of clinical signs. Survival times of several years are possible
result of aspiration of a pulmonary adenocarcinoma has after surgical excision. Ogilvie et al. (1989) reported that, of
been reported (Warren-Smith et al., 2011). This complica- 76 dogs with primary pulmonary adenocarcinoma, surgical
tion appears to be rare, but if the identified lesion will likely excision resulted in remission (i.e., elimination of all macro-
require surgical excision regardless of cause, the argument scopic evidence of tumor) in 55 dogs. The median survival
can be made to proceed directly to surgery. time of dogs that went into remission was 330 days, whereas
It may be appropriate to delay the collection of pulmonary the survival time in dogs that did not achieve remission was
specimens in asymptomatic animals with multifocal disease 28 days. At the completion of the study, 10 dogs remained
or in animals with significant unrelated problems. Rather, alive. McNiel et al. (1997) found that the histologic score of
radiographs are obtained again in 4 to 6 weeks to document the tumor, the presence of clinical signs, and regional lymph
the progression of lesions. Such delay is never recommended node metastases were significantly associated with the prog-
in dogs or cats with potentially resectable disease. nosis in 67 dogs with primary lung tumors. Median survival
The confirmation of malignant neoplasia in other organs times for dogs with and without clinical signs were 240 and
in conjunction with typical thoracic radiographic abnor- 545 days, respectively. Median survival times for dogs with
malities is often adequate for a presumptive diagnosis of and without lymph node involvement were 26 and 452 days,
pulmonary metastases. Overinterpretation of subtle radio- respectively. Median survival time for dogs with papillary
graphic lesions should be avoided. Conversely, the absence carcinoma was 495 days, compared with 44 days for dogs
of radiographic changes does not eliminate the possibility of with other histologic tumor types. Survival times ranged
metastatic disease. from 0 to 1437 days. A report of 21 cats with primary lung
Evaluation of the thorax by computed tomography should tumor described a median survival time of 115 days after
be considered in patients with known or suspected neopla- surgery (Hahn et al., 1998). Cats with moderately differenti-
sia. Computed tomography is much more sensitive than tho- ated tumors had a median survival time of 698 days (range,
racic radiography in the detection of metastatic disease (see 13-1526 days), whereas cats with poorly differentiated
Chapter 20). In patients with localized disease for whom tumors had a median survival time of 75 days (range, 13-634
surgical excision is being planned, computed tomography days). The prognosis for animals with multicentric neo-
provides more detailed anatomic information regarding the plasms is not known to depend on the presence or absence
involvement of adjacent structures and is more accurate in of pulmonary involvement.
identifying involvement of tracheobronchial lymph nodes,
compared with radiography.
PULMONARY HYPERTENSION
Treatment
Solitary pulmonary tumors are treated by surgical resection. Etiology
To obtain clear margins, usually the entire lung lobe that is Pulmonary hypertension is diagnosed when pulmonary sys-
involved must be excised. Lymph node biopsy specimens, as tolic pressure exceeds 30 mm Hg. The diagnosis is most
well as biopsy specimens from any grossly abnormal lung, accurately made by direct pressure measurements obtained
are obtained for histologic analysis. via cardiac catheterization—a procedure rarely performed in