Treatment
Therapy based on a definitive diagnosis is always preferable, and most likely to ensure the best outcome. However, in many cases owners do not have the financial resources to fund all the tests needed to reach a definitive diagnosis.
In cases like these, the author explains to owners that manageable ILDs generally respond to antibiotics/antiparasit- ics or corticosteroids. In rare cases, the author has diagnosed indolent bacterial infections fulminating as ILDs, especially in cats, but it bears mention that irrevocable pulmonary damage had been sustained in these cases. In some cases, especially in cats, if there is heart disease, it may be difficult to exclude cardiac causes of dyspnea without echocardiography, in which case a short trial of diuretics (furosemide) can be tried. Depending on the geographical location, parasitic migration (Dirofilariasis, Spirocerca lupi, Angiostrongylus vasorum, Paragonimus, Ancylostoma) may result in interstitial lung disease, and if there is a sufficient index of suspicion, it may be worthwhile treating with an appropriate therapeutic program for each of the aforementioned parasites. Treatment with either a macrocyclic lactone or febenda- zole may also be warranted as intestinal ver- minosis may have resulted in pulmonary parasitic migration. Infectious causes of ILDs include viruses (parainfluenza, distemper, adenovirus, influenza), and the vaccination status of the patient should be checked. Bacterial causes of ILD are probably rare, with Bordetella and Mycoplasma possibly being able to cause ILD. Bacteria may complicate ILDs, especially in cases of viral ILD, and therefore a judicious trial of antibiotics can be considered, if there is a clinical suspicion. In light of growing antibiotic resistance, the use of antibiotics should be carefully considered, and should be reserved for cases in which a reasonable possibility of a bacterial infection exists.Some cases of ILD, such as eosinophilic bronchopneumopathy (EB), may be exquisitely responsive to corticosteroids. The management of EB is beyond the scope of this chapter and the reader is referred elsewhere for a comprehensive review of the topic (Bexfield et al. 2006; Clercx and Peeters 2007; Mesquita et al. 2015).
ILDs are commonly associated with pulmonary hypertension (PH), which negatively impacts on the patient's quality of life (Heikkila-Laurila and Rajamaki 2014). A right-sided heart murmur and exercise intolerance should alert the clinician to the possibility of PH. Radiographic evidence of right heart enlargement, supports the diagnosis of PH, which is usually confirmed with echocardiography. Abrogation or attenuation of PH often significantly improves the patient's quality of life, even though it may not improve overall longevity. Based on the current evidence (which is scant) sildenafil is the drug of choice in managing PH, if the underlying cause cannot be addressed (Brown, Davison, and Sleeper 2010; Wung 2013). Another option is pimobendan, which has phosphodiesterase III inhibitory action. The author has used both of these drugs to manage PH. In the case of ILD such as pulmonary fibrosis the clinician should specifically screen for PH where possible, because it is commonly associated with this condition.
ILDs are typically monitored clinically, as there is limited value in serial evaluation of radiographs, BAL findings, or tissue sampling. Monitoring of the respiratory rate is a particularly useful appraisal of the respiratory system. In addition, reduction in the frequency of coughing (if present) or an improved tolerance of exercise, are also useful clinical indicators of improvement. Ultimately quality of life is the most important factor in the management of ILDs. Clinicians need to guide owners in the assessment of quality of life, as many owners do not have the medical background to appreciate the signs of suffering in their pets, and even compassionate owners may not appreciate the severity of a condition in pets that are still eating, or wag their tail when spoken to. The author finds that getting owners to keep a respiratory rate diary, and if present keeping a record of coughing and exercise tolerance, allows owners to visually track the progress of their pets, and provides objective data, rather than a subjective assessment of quality of life. In the case of PH, the author typically performs a repeat echocardiogram 2 weeks after instituting therapy. However, studies to date have failed to demonstrate the efficacy of drug therapy in reducing the echocardiographic severity of PH, but have shown an improvement in the quality of life, which re-emphasizes the importance of objectively assessing patient comfort as an overarching clinical assessment paradigm.