Page 377 - Small Animal Internal Medicine, 6th Edition

CHAPTER 22 Disorders of the Pulmonary Parenchyma and Vasculature 349

alveolar opacity and consolidation of the lung lobes can occur excessive bone marrow suppression resulting from the cyclo-
as well. phosphamide. Attempts to discontinue therapy can be made
VetBooks.ir diagnosis. In some cases, particularly those with bronchial after several months of remission. It may be necessary to
Pulmonary specimens must be examined to establish a
discontinue the cyclophosphamide earlier than this because
involvement, evidence of eosinophilic inflammation may be
cystitis. (See Chapter 77 for further discussion of the adverse
found in tracheal wash fluid. More aggressive techniques for long-term treatment is associated with sterile hemorrhagic
collecting pulmonary specimens, such as bronchoalveolar effects of cyclophosphamide therapy.) The effectiveness of
lavage, lung aspiration, or lung biopsy, are required to iden- other immunosuppressive drugs, such as cyclosporine, has
tify the eosinophilic response in other cases. Other inflam- not been reported.
matory cell populations are frequently present in lesser
numbers in such specimens. Prognosis
Potential antigen sources should be considered, and pul- A wide spectrum of disease is seen in terms of both the
monary specimens should be carefully examined for the severity of signs and the underlying causes. The prognosis is
presence of infectious agents and features of malignancy. generally fair to good. However, the prognosis is guarded in
Heartworm tests and fecal examinations for pulmonary par- dogs with severe eosinophilic pulmonary granulomatosis.
asites (including sedimentation, Baermann and flotation-
concentrating techniques) are indicated in all cases.
IDIOPATHIC INTERSTITIAL PNEUMONIAS
Treatment
Any primary disease identified during the diagnostic evalu- The term idiopathic interstitial pneumonia generally denotes
ation of these animals is treated directly. Eliminating the inflammatory infiltration and/or fibrosis of the lungs involv-
source of the antigen that may be triggering the excessive ing primarily the alveolar septa. Small airways, alveoli, and
immune response may result in a cure. the pulmonary vasculature may also be affected. The alveolar
Antiinflammatory therapy with glucocorticoids is indi- septa include alveolar epithelium, epithelial basal lamina,
cated for dogs in which an antigen source cannot be identi- capillary endothelial basal lamina, and capillary endothe-
fied, and for dogs with heartworm disease if the eosinophilic lium. Other cells include fibroblasts and alveolar macro-
inflammation is causing respiratory compromise (see phages. For a diagnosis of idiopathic disease, the known
Chapter 10). Dogs with eosinophilic granulomatosis often etiologies of interstitial lung disease must be ruled out as
require more aggressive immunosuppressive therapy. completely as possible. Causes of interstitial lung disease are
Dogs are typically treated with glucocorticoids, such as numerous and include many infectious agents and some
prednisone, at an initial dosage of 1 to 2 mg/kg orally every toxins and neoplasia.
12 hours. Clinical signs and thoracic radiographs are used to Idiopathic pulmonary fibrosis is the best described idio-
monitor the animal’s response to therapy, and initially these pathic interstitial pneumonia in dogs and cats. Some of the
should be assessed every 1 to 2 weeks. Once the clinical signs eosinophilic lung diseases (not including allergic or idio-
have completely resolved, the dosage of glucocorticoids is pathic feline bronchitis) may also be part of this group of
decreased to the lowest effective one. If signs have remained diseases. Other inflammatory lung diseases of the intersti-
in remission for 3 months, discontinuation of therapy can be tium in which a cause cannot be identified are occasionally
attempted. If signs are exacerbated by glucocorticoid therapy, seen in dogs and cats. The lesions may represent a form of
immediate reevaluation to search for underlying infectious vasculitis, a component of systemic lupus erythematosus,
agents is indicated. immune complex disease, or some other hypersensitivity
Inhaled steroids administered from a metered-dose response. These diseases are rare, however, and are not well
inhaler using a spacer and mask may be effective in control- documented. A lung biopsy must be performed for a defini-
ling signs, minimizing the systemic effects of oral steroids. tive diagnosis to be made. A clinical diagnosis is made only
This route of administration is most likely to be effective after extensive testing has been done to rule out more
in patients with predominantly bronchial involvement or common causes of lung disease, particularly infectious
to maintain remission of signs after initial treatment with agents and neoplasia, and after a prolonged positive response
oral steroids. The use of inhaled steroids is described in to immunosuppressive therapy.
detail with treatment for feline bronchitis (idiopathic) in
Chapter 21. IDIOPATHIC PULMONARY FIBROSIS
Dogs with large nodular lesions (eosinophilic granuloma- In people idiopathic pulmonary fibrosis is the clinical diag-
tosis) should be treated with a combination of glucocorti- nosis that is defined by the histopathologic diagnosis of usual
coids and a cytotoxic agent. Prednisone is administered to interstitial pneumonia. However, the histopathologic pattern
these animals at a dosage of 1 mg/kg orally every 12 hours, of usual interstitial pneumonia can be seen as a result of
in combination with cyclophosphamide at a dosage of other diseases; according to the American Thoracic Society/
2
50 mg/m orally every 48 hours. Clinical signs and thoracic European Respiratory Society/Japanese Respiratory Society/
radiographs are evaluated every 1 to 2 weeks until remission Latin American Thoracic Association consensus statement
is achieved. CBCs are also done every 1 to 2 weeks to detect (Raghu et al., 2011), the diagnosis of idiopathic pulmonary