Radiographic and histopathologic characteristics of pulmonary fibrosis in nine cats

A Retrospective Study of Sildenafil Administration in 55 Cats with Cardiopulmonary Disease (2009-2021)

Sildenafil is a drug used to successfully manage a variety of cardiopulmonary disorders in people and dogs, but there is limited information on its use in cats. The objective was to review the medical records of cats that received sildenafil as part of their clinical management. Medical records and pharmacy databases were searched for cats that received sildenafil for ≥24 h between 2009 and 2021, and data were collected from medical records. Fifty-five cats received sildenafil for ≥24 h and were included in the study: 43 with primary cardiac disease (acquired, n = 28; congenital, n = 15) and 12 with primary respiratory disease. Side effects possibly attributed to sildenafil were identified in two cats (systemic hypotension, n = 1; polydipsia, n = 1), and sildenafil was discontinued in the cat with hypotension. Sildenafil was discontinued in an additional three cats due to a lack of improvement in clinical signs. No cat was documented to develop worsening pulmonary edema within 72 h of starting sildenafil. Median duration of sildenafil administration was 87 days (range, 2-2362 days). Sildenafil administration in cats appeared to be generally well-tolerated. Studies are needed to determine whether sildenafil administration to cats with cardiopulmonary disease improves the quality of life or survival times.

Retrospective study of 540 cats with respiratory diseases in Japan (2003-2020)

BACKGROUND

Few epidemiological studies on respiratory medicine and the relationship between clinical signs and various respiratory diseases in cats have been reported.

OBJECTIVES

This retrospective study aimed to investigate the prevalence and breed predisposition to feline respiratory diseases in Japan and determine the association between clinical signs, duration and type of respiratory diseases.

METHODS

The medical records of cats with feline respiratory diseases were examined to obtain information on age, sex, breed, final diagnosis, clinical signs and duration. The odds ratios (ORs) and 95% confidence intervals were calculated to evaluate breed predispositions. Mann-Whitney U, Kruskal-Wallis and Dunn's tests were used to assess the duration of clinical signs.

RESULTS

This study included 540 cats with 615 respiratory diagnoses. The American Shorthair breed was predisposed to bronchopneumonia (BP; OR: 5.0) and pulmonary tumour (PT; OR: 3.6), while the Russian Blue breed exhibited a predisposition to inflammatory lower airway diseases (OR: 3.4), BP (OR: 6.1) and interstitial lung diseases (OR: 11.1). Similarly, the Scottish Fold breed displayed predisposition to PTs (OR: 5.8). The duration of clinical signs among nasal diseases, nasopharyngeal diseases and lower tracheal/bronchial and pulmonary diseases differed significantly (p = 0.001, p = 0.012, p < 0.0001, respectively).

CONCLUSIONS

The results suggest that some popular breeds in Japan are predisposed to feline respiratory diseases, especially the American Shorthair, Russian Blue and Scottish Fold breeds. The characteristics of occurrence, clinical signs and duration of each disease will aid in diagnosing, treating, preventing and elucidating the pathophysiology of feline respiratory disease.

Developmental lung disease in a cat associated with high probability of severe pulmonary hypertension: natural history, histopathology and genetic analysis

Case summary

This report describes the diagnostic findings, natural history and genetic analysis of the candidate gene Forkhead Box F1 (FOXF1) in a young cat with developmental lung disease and high probability of pulmonary hypertension. A 1-year-old male entire Chartreux cat was referred for cardiac murmur investigation and exercise intolerance. Echocardiography identified a high-velocity tricuspid regurgitant jet with right-sided cardiac changes, supporting a high probability of pulmonary hypertension. No congenital cardiac shunts or left-sided cardiac changes were found to support a primary cardiac cause of pulmonary hypertension. Extensive laboratory work, thoracic radiographs and CT were performed. Histopathological characterisation (lung biopsy and later post mortem) was necessary to reach the final diagnosis. Eight months after diagnosis, the cat developed right-sided congestive heart failure, eventually leading to euthanasia. Survival from diagnosis to death was 12 months.

Relevance and novel information

Developmental lung disease belongs to a group of diffuse lung diseases in humans associated with pulmonary hypertension. The veterinary literature describing lung growth disorders in cats is sparse, and the present report provides information on clinical presentation and progression alongside a thorough diagnostic workup, which may aid clinicians in identifying this condition. Lung biopsy was pivotal in reaching the final diagnosis. No causal variants in FOXF1 were identified.

Veterinary radiologic error rate as determined by necropsy

A large-scale postmortem auditing of antemortem imaging diagnoses has yet to be accomplished in veterinary medicine. For this retrospective, observational, single-center, diagnostic accuracy study, necropsy reports for patients of The Schwarzman Animal Medical Center were collected over a 1-year period. Each necropsy diagnosis was determined to be either correctly diagnosed or discrepant with its corresponding antemortem diagnostic imaging, and discrepancies were categorized. The radiologic error rate was calculated to include only clinically significant missed diagnoses (lesion was not reported but was retrospectively visible on the image) and misinterpretations (lesion was noted but was incorrectly diagnosed). Nonerror discrepancies, such as temporal indeterminacy, microscopic limitations, sensitivity limitations, and study-type limitations were not included in the error rate. A total of 1099 necropsy diagnoses had corresponding antemortem imaging; 440 diagnoses were classified as major diagnoses, of which 176 were discrepant, for a major discrepancy rate of 40%, similar to reports in people. Seventeen major discrepancies were diagnoses that were missed or misinterpreted by the radiologist, for a calculated radiologic error rate of 4.6%, comparable with error rates of 3%-5% reported in people. From 2020 to 2021, nearly half of all clinically significant abnormalities noted at necropsy went undetected by antemortem imaging, though most discrepancies owed to factors other than radiologic error. Identifying common patterns of misdiagnosis and discrepancy will help radiologists refine their analysis of imaging studies to potentially reduce interpretive error.

No evidence of pulmonary hypertension revealed in an echographic evaluation of right-sided hemodynamics in hyperthyroid cats

OBJECTIVES

Hyperthyroidism is a common endocrinopathy affecting middle-aged to elderly cats, with multisystemic repercussions. Hyperthyroid humans show decreased lung compliance and increased cardiac output with subsequent left heart failure leading to pulmonary capillary congestion. Prognosis worsens with the development of increased pulmonary vascular pressures (ie, pulmonary hypertension [PH]) in hyperthyroid humans. The effect of excess thyroid hormone concentration on pulmonary arterial hemodynamics is unknown in cats. Assessing pulmonary vascular pressures in veterinary medicine relies heavily on echocardiographic measurements performed at the level of the heart and pulmonary trunk. This study investigated right-sided cardiac and pulmonary arterial hemodynamics in hyperthyroid cats using echocardiography.

METHODS

Echocardiographic examinations of hyperthyroid cats identified through a bi-institutional database search were reviewed for the determination of systolic pulmonary arterial pressure (PAP) and 20 other metrics. Values were compared with those of a healthy cat group using non-parametric statistical analyses.

RESULTS

Systolic PAP could not be determined in 23/26 hyperthyroid and 13/14 healthy cats owing to unmeasurable tricuspid regurgitation flow velocity. Hyperthyroid cats were roughly twice as old (P <0.001) and had 2-4-fold higher respiratory rates (P <0.001) than healthy cats. Hyperthyroid cats showed an increase in acceleration time-to-ejection time ratio of pulmonary flow (1.4-fold, P = 0.001), pulmonary artery velocity time integral (1.2-1.6-fold, P = 0.001), maximal pulmonary velocity (1.3-1.7-fold, P = 0.002), stroke volume (1.5-fold, P = 0.001) and cardiac output (1.6-fold, P <0.001) vs healthy cats. None of the other echocardiographic metrics reached statistical significance.

CONCLUSIONS AND RELEVANCE

Systolic PAP estimation proved unsuitable as a sole measurement for the assessment of PH in hyperthyroid cats owing to the frequent inability to interrogate tricuspid regurgitant flow velocity. Hyperthyroid cats have altered echocardiographic measures of pulmonary hemodynamics dissimilar to those reported in hyperthyroid humans. Differential effects of thyrotoxic cardiomyopathy on ventricular systolic function may underlie species differences.

Feline pulmonary hypertension: are we overlooking an important comorbidity?

Pulmonary hypertension (PH) is a potential complication in many disease states, yet it has been largely overlooked in feline medicine. Recently, increased awareness of potential underlying causes has led to a wider understanding of the disease process in humans, with a focus on tailoring therapy to include specific treatment of the underlying etiology. Most of these treatments are not yet available in veterinary medicine, but as they move from the human to the veterinary field, it would be beneficial to better understand the forms of PH encountered in different species. Recently, diagnosis and classification of PH in dogs has been the focus of an American College of Veterinary Internal Medicine consensus statement, yet this condition has received little attention in cats. It is therefore our intention to raise awareness of this condition in cats and to propose a classification system for the types of PH seen in feline patients. As new medications are developed for the treatment of PH, it is important to recognize which forms of PH are seen in feline patients and understand the etiology of the disease. There are many reports of PH (or suspected PH based on echocardiographic assessment) in cats. In this review, we highlight the large number of conditions, and different etiologies, that are associated with PH. Improving understanding of this condition will bring us closer to being able to investigate the benefits of potential new diagnostics and therapies as they become available.

Imaging and endoscopic diagnosis of lung diseases in small animals. A review

Diagnostic imaging plays a fundamental role in the diagnosis of pulmonary diseases. Radiography, ultrasound, computed tomography, and endoscopy are important tools for achieving a diagnosis. The choice of diagnostic procedure varies according to the patient, the suspected diagnosis and the risk/benefit ratio. Culture, cytology and histology are nearly always necessary to obtain a definitive diagnosis. Several biopsy sampling techniques are described. Surgical biopsies are the gold standard for the diagnosis of bronchiolitis or interstitial lung diseases but often not performed due to the high risk. In humans, the introduction of transbronchial cryobiopsies has led to excellent results in the study of interstitial lung diseases.

Left Pulmonary Artery Coarctation Associated with Pneumonia and Pulmonary Hypertension in a Cat

A five-month-old European shorthair female kitten was referred because of recurrent episodes of respiratory distress. Results of physical examination, thoracic radiography, and echocardiography led to a presumptive diagnosis of severe precapillary pulmonary hypertension (PH) and interstitial pneumonia associated with right-sided cardiac remodeling. The cat rapidly died because of respiratory insufficiency. Pulmonary and cardiovascular pathological findings evidenced left pulmonary artery coarctation, severe right-sided cardiac hypertrophy, and bilateral pneumonia. This is the first report of pulmonary artery coarctation associated with pneumonia and PH in a cat.

Reversibility of clinical and computed tomographic lesions mimicking pulmonary fibrosis in a young cat

Background

In humans with idiopathic pulmonary fibrosis (IPF), specific thoracic computed tomographic (CT) features in the correct clinical context may be used in lieu of histologic examination. Cats develop an IPF-like condition with similar features to humans. As few cats have invasive lung biopsies, CT has appeal as a surrogate diagnostic, showing features consistent with architectural remodeling supporting “end-stage lung”.

Case presentation

A 1-year-old female spayed Domestic Shorthair cat presenting with progressive respiratory clinical signs and thoracic CT changes (reticular pattern, parenchymal bands, subpleural interstitial thickening, pleural fissure thickening, subpleural lines and regions of increased attenuation with traction bronchiectasis and architectural distortion) consistent with reports of IPF was given a grave prognosis for long-term survival. The cat was treated with prednisolone, fenbendazole, pradofloxacin and clindamycin. Five months later, while still receiving an anti-inflammatory dose of prednisolone, the cat was re-evaluated with owner-reported absent respiratory clinical signs. Thoracic CT demonstrated resolution of lung patterns consistent with fibrosis.

Conclusions

Fibrotic lung disease is irreversible. Despite this cat having compatible progressive respiratory signs and associated lung patterns on thoracic CT scan, these abnormalities resolved with non-specific therapy and time, negating the possibility of IPF. While the cause of the distinct CT lesions that ultimately resolved was not determined, infection was suspected. Experimental Toxocara cati infection shows overlapping CT features as this cat and is considered a treatable disease. Improvement of CT lesions months after experimental heartworm-associated respiratory disease in cats has been documented. Reversibility of lesions suggests inflammation rather than fibrosis was the cause of the thoracic CT lesions. This cat serves as a lesson that although thoracic CT has been advocated as a surrogate for histopathology in people with IPF, additional studies in cats are needed to integrate CT findings with signalment, other clinicopathologic features and therapeutic response before providing a diagnosis or prognosis of fibrotic lung disease.

Airway Remodeling in Feline Lungs

Airway remodeling encompass structural changes that occur as the result of chronic injury and lead to persistently altered airway structure and function. Although this process is known in several human respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD), airway remodeling is poorly characterized in the feline counterpart. In this study, we describe the spontaneous pulmonary changes in 3 cats paralleling the airway remodeling reported in humans. We observed airway smooth muscle cells (ASMCs) hyperplasia (peribronchial and interstitial), airway subepithelial and interstitial fibrosis, and vascular remodeling by increased number of vessels in the bronchial submucosa. The hyperplastic ASMCs co-expressed α-SMA, vimentin and desmin suggesting that vimentin, which is not normally expressed by ASMCs, may play a role in airway thickening, and remodeling. ASMCs had strong cytoplasmic expression of TGFβ-1, which is known to contribute to tissue remodeling in asthma and in various bronchial and interstitial lung diseases, suggesting its involvement in the pathogenesis of ASMCs hyperplasia. Our findings provide histologic evidence of airway remodeling in cats. Further studies on larger caseloads are needed to support our conclusions on the value of this feline condition as an animal model for nonspecific airway remodeling in humans.

Fatal Pulmonary Hypertension and Right-Sided Congestive Heart Failure in a Kitten Infected with Aelurostrongylus abstrusus

Simple Summary

Infections caused by lungworms are an emerging issue in feline medicine. Clinical features in cats may vary from subclinical infections to a severe disease, occasionally including fatal pneumonia, depending on different factors, e.g., lungworm species, parasitic burden, and age of the animal. A case of infection caused by Aelurostrongylus abstrusus in a domestic kitten presenting acute dyspnoea and ascites is presented here. Clinical, radiological, echocardiographic, parasitological, molecular, and pathological data are described. This is the first report of life-threatening pulmonary hypertension inducing congestive heart failure caused by A. abstrusus infection in a domestic kitten.

Abstract

Aelurostrongylus abstrusus is considered the most important respiratory nematode of domestic cats worldwide. This parasite inhabits the alveoli, alveolar ducts, and bronchioles and causes a subacute to chronic respiratory clinical disease. Clinical signs may occur in domestic cats of any age, though they are more often described in young animals. Physical examination, echocardiography, thoracic radiography, pulmonary and cardiac pathological findings, classical, and molecular parasitological analysis of a six-month-old kitten referred at the Veterinary Teaching Hospital of the University of Pisa (Italy) led to a diagnosis of parasitic bronchopneumonia caused by A. abstrusus, which was complicated by severe pulmonary hypertension (PH) and right-sided congestive heart failure (R-CHF) that caused the death of the animal. Cases of reversible PH associated with A. abstrusus infection have been seldom reported in cats. This is the first report of fatal PH and R-CHF in a kitten with clinical aelurostrongylosis.

Clinical, computed tomographic and histopathological findings in two cats with pulmonary fibrosis of unknown aetiology

Case series summary

Two cats were presented for further investigation of respiratory signs. One cat had a history of a cough and the other, tachypnoea. In each case, thoracic CT was performed, which revealed a generalised marked reticular pattern in the first cat and focal consolidation of the right caudal lung lobe in the second cat. The first cat was euthanased following completion of the imaging study and a post-mortem examination was performed. The second cat underwent surgical excision of the abnormal lung lobe and survived for 4 years after diagnosis. Histopathology performed on lung tissue removed from each cat was consistent with pulmonary fibrosis.

Relevance and novel information

This small case series adds to the existing literature and highlights the heterogeneous clinical course and variable appearance of pulmonary fibrosis on CT of affected cats. These cases provide evidence that pulmonary fibrosis in cats incorporates a wide spectrum of fibrotic lung disease and demonstrates the possibility for prolonged survival following diagnosis where disease is localised and amenable to surgical resection.

Perspectives in veterinary medicine: Description and classification of bronchiolar disorders in cats

This Perspectives in Veterinary Medicine article seeks to define, describe putative causes, and discuss key diagnostic tests for primary and secondary bronchiolar disorders to propose a classification scheme in cats with support from a literature review and case examples. The small airways (bronchioles with inner diameters <2 mm), located at the transitional zone between larger conducting airways and the pulmonary acinus, have been overlooked as major contributors to clinical syndromes of respiratory disease in cats. Because the trigger for many bronchiolar disorders is environmental and humans live in a shared environment with similar susceptibility, understanding these diseases in pet cats has relevance to One Health. Thoracic radiography, the major imaging modality used in the diagnostic evaluation of respiratory disease in cats, has low utility in detection of bronchiolar disease. Computed tomography (CT) with paired inspiratory and expiratory scans can detect pathology centered on small airways. In humans, treatment of bronchiolar disorders is not well established because of heterogeneous presentations and often late definitive diagnosis. A review of the human and veterinary medical literature will serve as the basis for a proposed classification scheme in cats. A case series of cats with CT or histopathologic evidence of bronchiolar lesions or both, either as a primary disorder or secondary to extension from large airway disease or interstitial lung disease, will be presented. Future multi‐institutional and multidisciplinary discussions among clinicians, radiologists, and pathologists will help refine and develop this classification scheme to promote early and specific recognition and optimize treatment.

Doppler-derived echocardiographic evidence of pulmonary hypertension in cats with left-sided congestive heart failure

INTRODUCTION

Pulmonary hypertension (PH) caused by left-sided congestive heart failure (L-CHF) is common in dogs and contributes to clinical signs and outcome. The aim of this study was to evaluate the prevalence of Doppler echocardiography-derived PH in a population of cats with L-CHF.

ANIMALS

The study involved 131 cats with L-CHF and 56 control cats.

METHODS

The study design is retrospective, observational study. Tricuspid regurgitation velocity, right atrial dimension, right ventricular (RV) dimension and function, RV wall thickness, pulmonary artery (PA) dimension, Doppler-derived systolic time intervals of PA flow, and presence of septal flattening were evaluated. Pulmonary hypertension was considered if tricuspid regurgitation velocity was >2.7 m/s.

RESULTS

Tricuspid regurgitation was present in 57/131 (44%) of cats with L-CHF and 24/56 (43%) in control cats based on color flow Doppler. Doppler-derived of PH was identified in 22/131 cats with L-CHF (17%). In 15/22 cats, PH was associated with cardiomyopathy, in 5/22 cases with congenital heart disease, and in 2/22 cases with other causes. Cats with Doppler-derived PH more often had chronic L-CHF, as opposed to acute L-CHF (p<0.05). All cats with Doppler-derived PH had subjectively-assessed right-sided heart enlargement, with larger right atrial and RV diameters (p<0.001), increased RV wall thickness (p<0.05), and higher prevalence of septal flattening (<0.001) and PA enlargement (p<0.05).

CONCLUSIONS

Pulmonary hypertension identified by Doppler echocardiography is not a common finding in cats with L-CHF. Right-sided heart enlargement, more frequently observed, may raise the suspicion of PH in cats with L-CHF.

Interstitial lung diseases in dogs and cats part I: The idiopathic interstitial pneumonias

Interstitial lung diseases (ILDs), also called diffuse parenchymal lung diseases, are a large heterogenous group of non-infectious, non-neoplastic disorders characterized by varied patterns of inflammation and fibrosis (Travis et al., 2002). In humans, accurate classification of interstitial lung diseases (ILDs) requires multidisciplinary collaboration between clinicians, radiologists and pathologists. The same is likely to be true for canine and feline ILDs; however, this collaborative approach is rarely taken, leading to a paucity of knowledge of ILDs in small animal species. A proposed classification scheme of canine and feline ILDs, modified from a human classification scheme, consists of three major groups: idiopathic interstitial pneumonias (IIPs), ILDs secondary to known causes, and miscellaneous ILDs (Travis et al., 2002). The focus of this review is on the IIPs in dogs and cats. A framework of what is known about the major IIPs in humans will be used to draw parallels when relevant to the canine and feline species. Differences will also be highlighted. When available from the veterinary literature, clinical presentation, diagnostic results, treatment and/or prognosis will be reported. The review underscores that to advance in our knowledge of veterinary IIPs and other ILDs, clinicopathologic features, advanced imaging and histopathology must be carefully integrated and larger groups of animals studied.

Dispneia expiratória restritiva em um gato com fibrose pulmonar idiopática: relato de caso

RESUMO As doenças pulmonares intersticiais constituem um grupo de doenças difusas do parênquima pulmonar, no qual a fibrose pulmonar intersticial está incluída. Histologicamente, esta se caracteriza por hiperplasia de pneumócitos tipo II, hiperplasia ou hipertrofia de músculo liso e fibrose. Embora a patogenia da fibrose pulmonar intersticial não esteja bem elucidada, devido às semelhanças microscópicas encontradas nos pneumócitos tipo II em felinos e na forma familiar da doença em humanos, acredita-se que haja caráter genético para o seu desenvolvimento. Os sinais clínicos frequentemente relatados incluem desconforto respiratório, cianose, letargia e perda de peso. Devido ao caráter progressivo e à ausência de tratamento específico, a doença apresenta prognóstico desfavorável. Foi atendida uma gata de 12 anos de idade, com histórico de dispneia há 20 dias. Ao exame clínico, o animal apresentou dispneia expiratória restritiva, crepitação à ausculta torácica e foi visualizado padrão intersticial ao exame radiográfico do tórax. A paciente foi submetida à punção com agulha fina de tecido pulmonar e veio a óbito algumas horas após o procedimento, apresentando insuficiência respiratória aguda. No exame histológico do tecido pulmonar, foi verificada a ocorrência de fibrose pulmonar idiopática. O objetivo do presente trabalho é relatar um caso de dispneia expiratória restritiva em um felino doméstico devido à fibrose pulmonar idiopática, já que, segundo o conhecimento dos autores, não há nenhum relato da ocorrência da doença no país.

Academic and private practice partnerships in veterinary radiology residency training

As veterinary radiologists devote greater time to telemedicine consultation, residency training must evolve to reflect the skills of these services. The contribution of private practice/consultant radiologists to residency training has traditionally been minimal but academic and private practice partnerships in education and research can provide the framework for a well-rounded residency. These partnerships can also lessen the impact of workforce shortages in academia and provide financial compensation to academicians through external consultation. The purpose of this commentary is to review existing collaborative interactions between academic and private practice veterinary radiologists; with a focus on ways to sustain, improve, and cautiously increase the number of veterinary radiology training programs.

Computed tomography, radiology and echocardiography in cats naturally infected with Aelurostrongylus abstrusus

Objectives The aims of the study were to describe the radiographic and computed tomographic features in cats naturally infected with Aelurostrongylus abstrusus, and to identify signs of pulmonary hypertension with echocardiography. Methods Fourteen cats positive on Baermann test for A abstrusus were included in the study. All cats underwent thoracic radiography, CT and echocardiography. Results The most common clinical signs were coughing (10/14) and dyspnoea (5/14). Radiographic findings included a generalised unstructured interstitial pulmonary pattern (8/14), mixed bronchointerstitioalveolar pattern (3/14) and bronchointerstitial pattern with bronchial wall thickening (3/14). Sternal lymphadenopathy was detected on thoracic radiographs in six cats. On CT, features were mixed bronchointerstitioalveolar pattern with ground-glass appearance in six cats, interstitioalveolar with multiple pulmonary nodules in five, interstitial ground-glass infiltrates in three, regional lymph node enlargement in 11 (10 sternal, three cranial mediastinal and three tracheobronchial lymph nodes) and subpleural thickening in four. None of the thoracic radiographs revealed subpleural thickening. In all cases, pulmonary vessels were normal in terms of size, shape and attenuation on both radiography and CT. Pulmonary hypertension and cardiac abnormalities were not observed in any cat during echocardiography. Conclusions and relevance CT provided a more thorough characterisation of pulmonary and mediastinal lesions compared with thoracic radiographs in cats naturally infected with A abstrusus. Although feline aelurostrongylosis has been previously associated with histopathological lesions in lung arteries, in this cohort clinical evidence of pulmonary hypertension was not documented.

Vasoproliferative process resembling pulmonary capillary hemangiomatosis in a cat

BACKGROUND

Pulmonary capillary hemangiomatosis is a rare, vascular obstructive disorder that uniformly causes pulmonary arterial hypertension. Clinically, pulmonary capillary hemangiomatosis is indistinguishable from primary pulmonary arterial hypertension and histology is required for definitive diagnosis. The distinctive histologic feature of pulmonary capillary hemangiomatosis is non-malignant extensive proliferation of capillaries in the alveolar septae. Vasodilator treatment of humans with primary arterial hypertension due to pulmonary capillary hemangiomatosis can result in fatal acute pulmonary edema. Computed tomography is thus critical to discern pulmonary capillary hemangiomatosis from other causes of pulmonary arterial hypertension prior to vasodilator therapy. This is the first report of a vasoproliferative process resembling pulmonary capillary hemangiomatosis in the feline species.

CASE PRESENTATION

A 15-year-old, male castrated, domestic shorthair cat presented for persistent labored breathing presumptively due to congestive heart failure despite treatment with diuretics for 7 days. Echocardiography showed evidence of hypertrophic cardiomyopathy with severe pulmonary hypertension; however, a normal sized left atrium was not consistent with congestive heart failure. Thoracic computed tomography was performed and showed evidence of diffuse ill-defined nodular ground glass opacities, enlarged pulmonary arteries, and filling defects consistent with pulmonary thromboembolism. The cat acutely decompensated after a single dose of sildenafil and was euthanized. Histopathology of the lungs showed severe multifocal alveolar capillary proliferation with respiratory bronchiolar infiltration, marked type II pneumocyte hyperplasia and multifocal pulmonary arterial thrombosis.

CONCLUSION

This is the first description in a cat of a vasoproliferative disorder resembling pulmonary capillary hemangiomatosis complicated by multifocal pulmonary arterial thrombosis. Inspiratory and expiratory ventilator-driven breath holds with angiography revealed lesions predominantly characterized by ground glass opacification and vascular filling defects with absence of air trapping. The results from this report suggest that, as in humans, the cat can develop a pulmonary capillary hemangiomatosis-like disease in which vasodilator therapy to address pulmonary hypertension may lead to fatal pulmonary edema.

Studying human respiratory disease in animals--role of induced and naturally occurring models

Respiratory disorders like asthma, emphysema, and pulmonary fibrosis affect millions of Americans and many more worldwide. Despite advancements in medical research that have led to improved understanding of the pathophysiology of these conditions and sometimes to new therapeutic interventions, these disorders are for the most part chronic and progressive; current interventions are not curative and do not halt disease progression. A major obstacle to further advancements relates to the absence of animal models that exactly resemble the human condition, which delays the elucidation of relevant mechanisms of action, the unveiling of biomarkers of disease progression, and identification of new targets for intervention in patients. There are currently many induced animal models of human respiratory disease available for study, and even though they mimic features of human disease, discoveries in these models have not always translated into safe and effective treatments in humans. A major obstacle relates to the genetic, anatomical, and functional variations amongst species, which represents the major challenge to overcome when searching for appropriate models of respiratory disease. Nevertheless, rodents, in particular mice, have become the most common species used for experimentation, due to their relatively low cost, size, and adequate understanding of murine genetics, among other advantages. Less well known is the fact that domestic animals also suffer from respiratory illnesses similar to those found in humans. Asthma, bronchitis, pneumonia, and pulmonary fibrosis are among the many disorders occurring naturally in dogs, cats, and horses, among other species. These models might better resemble the human condition and are emphasized here, but further investigations are needed to determine their relevance.

A case of atypical diffuse feline fibrotic lung disease

An 11-year-old cat presented for respiratory distress and weight loss. Thoracic radiographs were interpreted as a diffuse bronchointerstitial pattern with bronchiectasis and a mild ventral alveolar pattern on the lateral views. Computed tomography revealed a severe diffuse reticular pattern, relatively hyperattenuating in subpleural regions, with diffuse traction bronchiectasis and some degree of honeycombing. Despite the absence of basal predominance, this pattern was considered to be suggestive of usual interstitial pneumonia (UIP). Other differentials (other types of interstitial lung disease, infectious pneumonitis, neoplasia, or early edema or hemorrhage) were considered less likely based on history and other test results. The cat was discharged without any treatment, and euthanased 5 months later. Post-mortem histological analysis of the lung revealed end-stage lung, with extensive fibrosis that was more severe in subpleural regions, fibroblastic foci and honeycombing, suggestive of UIP. A probable diagnosis of idiopathic pulmonary fibrosis (IPF) was made. The diffuse distribution of the lesions was atypical compared with previous tomographic and histologic descriptions of IPF in cats. This case report suggests a heterogeneity of the pulmonary fibrotic disorders in cats that warrants further investigation for better characterization and classification.