Pulmonary interstitial emphysema and spontaneous pneumomediastinum are more prevalent in sighthounds than other dog breeds undergoing thoracic CT.

Spontaneous pneumomediastinum is an uncommon condition described in veterinary medicine with concurrent respiratory disease. It can be caused by the Macklin effect, which is when gas leaks from the alveoli into the surrounding interstitial lung tissue. Pulmonary interstitial emphysema (PIE) is the presence of gas within the pulmonary vascular sheaths and indicates the presence of the Macklin effect. In the authors' experience, spontaneous pneumomediastinum and PIE are more prevalent in sighthound dogs than in other breeds and are often considered incidental findings. This retrospective, observational, cross-sectional study compared the prevalence of PIE and subsequent pneumomediastinum in sighthound with other purebred dogs. It characterized the appearance of PIE in CT and analyzed a possible association with concomitant pulmonary pathologies or with the use of general anesthesia. Medical records and thoracic CTs of sighthounds and nonsighthound dogs from two institutions were reviewed. A total of 256 dogs, comprising 127 sighthounds and 129 other purebred dogs, were included. The prevalence of PIE and pneumomediastinum was statistically higher in sighthound (14.2%) compared with other nonsighthound dogs (2.2%). There was no statistical association between the presence of PIE and pneumomediastinum with different age and weight groups or with sex. There was no statistical difference in the prevalence of PIE and pneumomediastinum between dogs with and without pulmonary pathology or in dogs undergoing CT with sedation or general anesthesia. Spontaneous pneumomediastinum in sighthounds is more prevalent than in other breeds, and its prevalence is not associated with the presence of pulmonary pathology or the use of general anesthesia.

Classification of the quality of canine and feline ventrodorsal and dorsoventral thoracic radiographs through machine learning.

Thoracic radiographs are an essential diagnostic tool in companion animal medicine and are frequently used as a part of routine workups in patients presenting for coughing, respiratory distress, cardiovascular diseases, and for staging of neoplasia. Quality control is a critical aspect of radiology practice in preventing misdiagnosis and ensuring consistent, accurate, and reliable diagnostic imaging. Implementing an effective quality control procedure in radiology can impact patient outcomes, facilitate clinical decision-making, and decrease healthcare costs. In this study, a machine learning-based quality classification model is suggested for canine and feline thoracic radiographs captured in both ventrodorsal and dorsoventral positions. The problem of quality classification was divided into collimation, positioning, and exposure, and then an automatic classification method was proposed for each based on deep learning and machine learning. We utilized a dataset of 899 radiographs of dogs and cats. Evaluations using fivefold cross-validation resulted in an F1 score and AUC score of 91.33 (95% CI: 88.37-94.29) and 91.10 (95% CI: 88.16-94.03), respectively. Results indicated that the proposed automatic quality classification has the potential to be implemented in radiology clinics to improve radiograph quality and reduce nondiagnostic images.

Vertebral heart size and vertebral left atrial size reference ranges in healthy Miniature Schnauzers.

OBJECTIVE: The inclusion of vertebral heart score (VHS) and, more recently, the inclusion of the vertebral left atrial size (VLAS) in radiographic evaluation have become important screening tools for identifying dogs with occult cardiac disease. Several recent papers have shown there are interbreed variations in the VHS reference range. Our hypothesis is that the Miniature Schnauzer would also have a higher reference range for its VHS. ANIMALS: The electronic medical records of IDEXX Telemedicine Consultants were searched for Miniature Schnauzers undergoing thoracic radiographs between March 1, 2022, and February 28, 2023. METHODS: Dogs were included if they had 3 view thoracic radiographs performed and no evidence of cardiopulmonary disease was detected. Dogs with incomplete radiographic studies or cardiac or extracardiac disease were excluded. The VHS and VLAS measurements were performed by 2 board-certified cardiologists independent of one another. RESULTS: A total of 1,000 radiographs were obtained of which 272 were included for the study. The overall range for the VHS in this cohort was 9.68 to 12.07 with a median of 10.9. For VLAS measurements, a range of 1.71 to 2.4 was documented with a median of 2.0. CLINICAL RELEVANCE: The VHS for Miniature Schnauzers without cardiac disease was confirmed to be higher than the canine reference range.

Radiographic and computed tomographic characteristics of intraluminal tracheal adenoma in a cat.

A 13-year-old spayed female Persian cat presented with dyspnea and nasal discharge. Thoracic radiography revealed a dome-shaped soft-tissue opacity in the carina. Computed tomography confirmed a soft tissue-attenuating mass in the carina and the left and right proximal main bronchi that appeared to arise from the tracheal wall. Tracheoscopy revealed an intraluminal broad-based mass with multilobulated borders at the same location. Histopathological evaluation revealed a benign neoplastic process of the glandular epithelial lineage, which was considered an adenoma. Tracheal adenomas should be included in the differential diagnosis of tracheal masses.

Physical examination and CT to assess thoracic injury in 137 cats presented to UK referral hospitals after trauma.

OBJECTIVES: The aim of the study was to describe clinical examination and thoracic CT (TCT) findings in cats after trauma, and to identify physical examination findings associated with both abnormalities on TCT and the need for therapeutic interventions. METHODS: A multicentre, retrospective, observational study was conducted. Cats admitted to the participating hospitals with a history of blunt trauma and that underwent TCT were eligible. Data were collected on signalment, history, physical examination, TCT findings and subsequent interventions. RESULTS: In total, 137 cats were included. Road traffic accidents (RTAs) were the most frequently reported cause of trauma (69%). Tachypnoea (32%), pale mucous membranes (22%) and dyspnoea (20%) were the most common abnormal findings on thoracic examination. The most frequently identified thoracic pathologies on TCT were atelectasis (34%), pulmonary contusions (33%), pneumothorax (29%) and pleural effusion (20%). Thoracocentesis was the most commonly performed intervention (12%), followed by chest drain placement (7%). A total of 45 (33%) cats had no physical examination abnormalities but did have abnormalities detected on TCT; six of these cats required interventions. Increasing numbers of thoracic abnormalities on clinical examination were associated with increasing likelihood of having abnormal findings on TCT (odds ratio [OR] 2.04, 95% confidence interval [CI] 1.21-3.44, P = 0.008) and of requiring an intervention (OR 1.82, 95% CI 1.32-2.51, P <0.001). CONCLUSIONS AND RELEVANCE: RTAs were the most common reported cause of blunt trauma. Atelectasis, pulmonary contusions and pneumothorax were the most common abnormalities identified on TCT, and thoracic drainage was the most utilised intervention. TCT may be useful in identifying cats with normal thoracic physical examination findings that have significant thoracic pathology, and a high number of abnormal findings on thoracic examination should raise suspicion for both minor and major thoracic pathology. The results of this study can be used to assist in selecting appropriate cases for TCT after blunt trauma.

An AI-based algorithm for the automatic evaluation of image quality in canine thoracic radiographs.

The aim of this study was to develop and test an artificial intelligence (AI)-based algorithm for detecting common technical errors in canine thoracic radiography. The algorithm was trained using a database of thoracic radiographs from three veterinary clinics in Italy, which were evaluated for image quality by three experienced veterinary diagnostic imagers. The algorithm was designed to classify the images as correct or having one or more of the following errors: rotation, underexposure, overexposure, incorrect limb positioning, incorrect neck positioning, blurriness, cut-off, or the presence of foreign objects, or medical devices. The algorithm was able to correctly identify errors in thoracic radiographs with an overall accuracy of 81.5% in latero-lateral and 75.7% in sagittal images. The most accurately identified errors were limb mispositioning and underexposure both in latero-lateral and sagittal images. The accuracy of the developed model in the classification of technically correct radiographs was fair in latero-lateral and good in sagittal images. The authors conclude that their AI-based algorithm is a promising tool for improving the accuracy of radiographic interpretation by identifying technical errors in canine thoracic radiographs.

Performance of a commercially available artificial intelligence software for the detection of confirmed pulmonary nodules and masses in canine thoracic radiography.

Advancements in the field of artificial intelligence (AI) are modest in veterinary medicine relative to their substantial growth in human medicine. However, interest in this field is increasing, and commercially available veterinary AI products are already on the market. In this retrospective, diagnostic accuracy study, the accuracy of a commercially available convolutional neural network AI product (Vetology AI®) is assessed on 56 thoracic radiographic studies of pulmonary nodules and masses, as well as 32 control cases. Positive cases were confirmed to have pulmonary pathology consistent with a nodule/mass either by CT, cytology, or histopathology. The AI software detected pulmonary nodules/masses in 31 of 56 confirmed cases and correctly classified 30 of 32 control cases. The AI model accuracy is 69.3%, balanced accuracy 74.6%, F1-score 0.7, sensitivity 55.4%, and specificity 93.75%. Building on these results, both the current clinical relevance of AI and how veterinarians can be expected to use available commercial products are discussed.

Machine learning can appropriately classify the collimation of ventrodorsal and dorsoventral thoracic radiographic images of dogs and cats.

OBJECTIVES: To determine the feasibility of machine learning algorithms for the classification of appropriate collimation of the cranial and caudal borders in ventrodorsal and dorsoventral thoracic radiographs. SAMPLES: 900 ventrodorsal and dorsoventral canine and feline thoracic radiographs were retrospectively acquired from the Picture Archiving and Communication system (PACs) system of the Ontario Veterinary College. PROCEDURES: Radiographs acquired from April 2020 to May 2021 were labeled by 1 radiologist in Summer of 2022 as either appropriately or inappropriately collimated for the cranial and caudal borders. A machine learning model was trained to identify the appropriate inclusion of the entire lung field at both the cranial and caudal borders. Both individual models and a combined overall inclusion model were assessed based on the combined results of both the cranial and caudal border assessments. RESULTS: The combined overall inclusion model showed a precision of 91.21% (95% CI [91, 91.4]), accuracy of 83.17% (95% CI [83, 83.4]), and F1 score of 87% (95% CI [86.8, 87.2]) for classification when compared with the radiologist's quality assessment. The model took on average 6 ± 1 second to run. CLINICAL RELEVANCE: Deep learning-based methods can classify small animal thoracic radiographs as appropriately or inappropriately collimated. These methods could be deployed in a clinical setting to improve the diagnostic quality of thoracic radiographs in small animal practice.

Providing comparison normal examples alongside pathologic thoracic radiographic cases can improve veterinary students' ability to identify abnormal findings or diagnose disease.

Learning by comparison is a frequently employed education strategy used across many disciplines and levels. Interpreting radiographs requires both skills of perception and pattern recognition, which makes comparison techniques particularly useful in this field. In this randomized, prospective, parallel-group study, students enrolled in second and third-year radiology veterinary courses were given a case-based thoracic radiographic interpretation assignment. A cohort of the participants was given cases with side-by-side comparison normal images while the other cohort only had access to the cases. Twelve cases in total were presented to the students, with 10 cases depicting examples of common thoracic pathologies, while 2 cases were examples of normal. Radiographs of both feline and canine species were represented. Correctness of response to multiple choice questions was tracked, as was year and group (group 1: non compare, Control; group 2: compare, Intervention). Students assigned to group 1 had a lower percentage of correct answers than students assigned to group 2 (45% Control vs. 52% Intervention; P = 0.01). This indicates that side-by-side comparison to a normal example is helpful in identifying disease. No statistical significance was noted for the correctness of responses according to the year of training (P = 0.90). The overall poor performance on the assignment, regardless of group or year, shows that students in the early years of undergraduate veterinary radiology training struggle with the interpretation of common pathologies, likely a result of a lack of exposure to a multitude of cases and normal variants.

The effect of different body positions on the cardiothoracic ratios obtained by chest radiography in Japanese macaques (Macaca fuscata) and rhesus macaques (Macaca mulatta).

BACKGROUND: Although some studies have reported cardiac diseases in macaques, an adequate screening method for cardiac enlargement has not yet been established. This study aimed to evaluate the positioning of macaques for radiographs and establish reference intervals for the cardiothoracic ratio (CTR). MATERIALS AND METHODS: We developed a device for chest radiography in the sitting position and performed chest radiography in 50 Japanese and 48 rhesus macaques to evaluate the CTR and chest cavity size. RESULTS: In Japanese and rhesus macaques, the thorax height was significantly larger, the heart width was significantly smaller, and the mean CTR was significantly smaller in the sitting position than in the prone position. The reference intervals for CTR in the sitting position were 51.6 ± 4.6% and 52.2 ± 5.1% in Japanese and rhesus macaques, respectively. CONCLUSION: Thoracic radiographic images obtained in a sitting position resulted in a smaller CTR and a larger thorax height, which could be useful for detecting pulmonary and cardiac abnormalities.

Accuracy of artificial intelligence software for the detection of confirmed pleural effusion in thoracic radiographs in dogs.

The use of artificial intelligence (AI) algorithms in diagnostic radiology is a developing area in veterinary medicine and may provide substantial benefit in many clinical settings. These range from timely image interpretation in the emergency setting when no boarded radiologist is available to allowing boarded radiologists to focus on more challenging cases that require complex medical decision making. Testing the performance of artificial intelligence (AI) software in veterinary medicine is at its early stages, and only a scant number of reports of validation of AI software have been published. The purpose of this study was to investigate the performance of an AI algorithm (Vetology AI® ) in the detection of pleural effusion in thoracic radiographs of dogs. In this retrospective, diagnostic case-controlled study, 62 canine patients were recruited. A control group of 21 dogs with normal thoracic radiographs and a sample group of 41 dogs with confirmed pleural effusion were selected from the electronic medical records at the Cummings School of Veterinary Medicine. The images were cropped to include only the area of interest (i.e., thorax). The software then classified images into those with pleural effusion and those without. The AI algorithm was able to determine the presence of pleural effusion with 88.7% accuracy (P < 0.05). The sensitivity and specificity were 90.2% and 81.8%, respectively (positive predictive value, 92.5%; negative predictive value, 81.8%). The application of this technology in the diagnostic interpretation of thoracic radiographs in veterinary medicine appears to be of value and warrants further investigation and testing.

Septic pericardial disease and mediastinal abscessation in a cat with an intrathoracic needle foreign body.

OBJECTIVE: To describe the successful management of a cat with an intrathoracic sewing needle foreign body and septic pericardial effusion. CASE SUMMARY: A 10-year-old neutered female domestic longhair cat was referred for an intrathoracic metallic foreign body identified via thoracic radiography. Two weeks prior, the cat may have ingested a sewing needle. She was presented hemodynamically unstable; point-of-care thoracic ultrasound identified pericardial effusion with right atrial tamponade. Pericardiocentesis stabilized hemodynamic parameters. The effusion was grossly purulent, and bacterial culture grew an Actinomyces sp. The cat underwent a median sternotomy to remove the foreign body, debride associated mediastinal abscesses, and perform a partial pericardiectomy. Over the next 10 days, the cat was managed in hospital with a left unilateral thoracostomy tube and intermittent lavage of the pleural cavity. The cat was discharged, and follow-up at 7 days showed no evidence of pericardial or pleural effusion. NEW OR UNIQUE INFORMATION PROVIDED: Contrary to previous reports, this case shows that extra-gastrointestinal, specifically intrathoracic, sewing needle foreign bodies can cause significant morbidity in cats. To the authors' knowledge, this report is the first to describe septic pericardial disease resulting from documented foreign body ingestion in the cat. It is also the first case report of successful surgical management of mediastinal abscessation in the cat.

Bilateral thoracic radiographs increase lesion detection in horses with pneumonia or pulmonary neoplasia but do not bring any additional benefit for inflammatory or diffuse pulmonary disease.

Published studies describing the effects of bilateral radiographic projections on the detection of equine pulmonary lesions are currently lacking. The objectives of this retrospective, single center, observational study were to compare unilateral and bilateral thoracic radiographic projections for the detection of pulmonary lesions in a group of horses. Based on their clinical diagnosis, 167 adults and foals with bilateral thoracic radiographs were classified as having pneumonia (n = 88), inflammatory or diffuse pulmonary disease (n = 72), and pulmonary masses (n = 7). After an initial interrater repeatability test, right-to-left and left-to-right projections were anonymized and independently interpreted by a radiologist blinded to the clinical diagnosis. Scores were attributed for each pattern/lesion (alveolar, interstitial, bronchial, nodules/masses, cavitary lesions) and each quadrant. Agreement between scores from each projection was evaluated with Bland-Altman plots. Lesions identified on one side but not on the contralateral projection were considered discordant. There was no preferential lateralization of pulmonary lesions. The prevalence of discordance was 14.4%, 9.0%, and 4.2% for alveolar pattern, nodules/masses, and cavitary lesions, respectively. Up to nine horses (10.2%) with pneumonia could have been misdiagnosed. A pulmonary mass would have been missed in one case. For inflammatory or diffuse disease, discordance was slight, and the addition of contralateral projections had no impact on radiographic interpretation. In conclusion, in horses with pneumonia or neoplasia, bilateral projections, or adding at least one contralateral caudoventral view, increased the probability of identifying pulmonary lesions. In horses with inflammatory or diffuse disease, bilateral thoracic radiography provided no additional benefit.

Comparison of error rates between four pretrained DenseNet convolutional neural network models and 13 board-certified veterinary radiologists when evaluating 15 labels of canine thoracic radiographs.

Convolutional neural networks (CNNs) are commonly used as artificial intelligence (AI) tools for evaluating radiographs, but published studies testing their performance in veterinary patients are currently lacking. The purpose of this retrospective, secondary analysis, diagnostic accuracy study was to compare the error rates of four CNNs to the error rates of 13 veterinary radiologists for evaluating canine thoracic radiographs using an independent gold standard. Radiographs acquired at a referral institution were used to evaluate the four CNNs sharing a common architecture. Fifty radiographic studies were selected at random. The studies were evaluated independently by three board-certified veterinary radiologists for the presence or absence of 15 thoracic labels, thus creating the gold standard through the majority rule. The labels included "cardiovascular," "pulmonary," "pleural," "airway," and "other categories." The error rates for each of the CNNs and for 13 additional board-certified veterinary radiologists were calculated on those same studies. There was no statistical difference in the error rates among the four CNNs for the majority of the labels. However, the CNN's training method impacted the overall error rate for three of 15 labels. The veterinary radiologists had a statistically lower error rate than all four CNNs overall and for five labels (33%). There was only one label ("esophageal dilation") for which two CNNs were superior to the veterinary radiologists. Findings from the current study raise numerous questions that need to be addressed to further develop and standardize AI in the veterinary radiology environment and to optimize patient care.

Vertebral heart size and vertebral left atrial size reference ranges in healthy Maltese dogs.

The most common cardiac measurements on thoracic radiography in veterinary medicine are vertebral heart size (VHS) and vertebral left atrial size (VLAS). Previously published studies have demonstrated evidence that reference ranges for these measures vary among different dog breeds, however reference ranges for Maltese breed dogs are currently lacking. We hypothesized that VHS and VLAS in healthy Maltese dogs would not be influenced by sex, age, or bodyweight. This retrospective, reference interval study aimed to describe reference intervals for VHS and VLAS in a sample of clinically healthy Maltese dogs and assess the intra- and interobserver variabilities for VLAS and VHS measurements. A total of 81 clinically healthy Maltese dogs were included, with healthy status being based on a complete cardiologic examination. Thoracic radiography in right lateral recumbency was performed for all dogs. The intra- and interobserver variability assessments of VHS and VLAS were based on measurements independently performed by three observers. The mean VHS was 9.53 ± 0.46 vertebrae (v). The median and interquartile range (IQR) for VLAS was 2 v (IQR, 1.8-2.1v). A statistically significant moderate positive correlation was observed between VHS and VLAS (P < .01, r = 0.416). Both VHS and VLAS showed an almost perfect intraobserver agreement. Interobserver agreement was almost perfect for VHS and substantial for VLAS. Findings supported previous studies recommending the use of breed-specific reference values for VHS and VLAS, and provided background data for future radiographic evaluations of Maltese dogs with clinical signs of cardiac disease.

Achados radiográficos e ultrassonográficos de fibrossarcoma em membro torácico de gatos: relato de três casos / Radiographic and ultrasound findings of fibrosarcoma in the cats: reports of three cases / Hallazgos radiográficos y ultrasonidos de fibrosarcoma en la extremidad torácica de gatos: informe de tres casos

O fibrossarcoma é uma neoplasia mesenquimal maligna originada dos fibroblastos que localiza-se especificamente em tecido cutâneo, subcutâneo e cavidade oral. A ressecção cirúrgica do tumor com margem de segurança é conhecida como a principal forma de tratamento. A principal forma de metástase é a via hematógena, atingindo pulmões, e menos comum em linfonodos regionais. A análise histopatológica é o exame diagnóstico de eleição para definição do tipo de tumor e sua graduação. Os exames de imagem são fundamentais no estadiamento das neoplasias e planejamento cirúrgico. A ultrassonografia e radiografia são os métodos mais utilizados e oferecem um grande apoio a oncologia médica veterinária. O exame radiográfico possibilita o achado de neoformações ósseas ou demais alterações como o aumento de volume de tecidos moles, infiltração gordurosa, e cavitações com gás ou fluído. O exame ultrassonográfico permite o conhecimento sobre a ecotextura, organização, e localização da lesão em tecidos moles. Em três gatos com fibrosssarcoma em membro torácico, foram realizadas radiografia e ultrassonografia específica da lesão. Os achados radiográficos foram aumento de volume, radiopacidade dos tecidos moles, sem acometimento ósseo. Os achados ultrassonográficos foram lesões de ecotextura grosseira, altamente heterogêneas. Os exames citológicos e histopatológicos revelaram tratar-se de fibrossarcoma. O presente relato tem como objetivo descrever os achados radiográficos e ultrassonográficos de fibrossarcoma em membro torácico de três gatos.

Fibrosarcoma is a malignant mesenchymal neoplasm originating from fibroblasts, which is specifically located in the skin tissue, subcutaneous tissue and oral cavity. Surgical resection of the tumor with a safety margin is known as the main form of treatment. The main form of metastasis is the hematogenous route, reaching the lungs, and less common in regional lymph nodes. histopathological analysis is the diagnostic test of choice for defining the type of tumor and its graduation. Imaging exams are essential in the staging of neoplasms and surgical planning. Ultrasonography and radiography are the most used methods and offer great support to veterinary medical oncology. The radiographic exam allows the finding of bone neoformations or other alterations such as the increase in soft tissue volume, fatty infiltration, and cavitations with gas or fluid. The ultrasound examination allows knowledge about the echotexture, organization, and location of the soft tissue lesion. Three cats with fibrosarcoma in the thoracic limb underwent lesion-specific radiography and ultrasound. The radiographic findings of fibrosarcomas were increased soft tissue radiopacity volume, without bone involvement. And the ultrasonographic findings were gross echotexture lesions, highly heterogeneous. Cytological and histopathological examinations were performed for definitive diagnosis. The present report aims to describe the radiographic and ultrasonographic findings of fibrosarcoma in the thoracic limb of three cats.

RESUMEN El fibrosarcoma es una neoplasia mesenquimatosa maligna que se origina a partir de fibroblastos, que se localiza específicamente en el tejido cutáneo, tejido subcutáneo y cavidad oral. La resección quirúrgica del tumor con un margen de seguridad se conoce como la forma principal de tratamiento. La principal forma de metástasis es la vía hematógena, que llega a los pulmones y es menos común en los ganglios linfáticos regionales. El análisis histopatológico es la prueba diagnóstica de elección para definir el tipo de tumor y su graduación. Los exámenes por imágenes son esenciales en la estadificación de las neoplasias y la planificación quirúrgica. La ecografía y la radiografía son los métodos más utilizados y ofrecen un gran apoyo a la oncología médica veterinaria. El examen radiográfico permite encontrar neoformaciones óseas u otras alteraciones como aumento de volumen de tejidos blandos, infiltración grasa y cavitaciones con gas o líquido. El examen ecográfico permite conocer la ecotextura, organización y ubicación de la lesión de tejidos blandos. A tres gatos con fibrosarcoma en la extremidad torácica se les realizó una radiografía y una ecografía específicas de la lesión. Los hallazgos radiográficos de los fibrosarcomas fueron un aumento del volumen de radiopacidad de los tejidos blandos, sin afectación ósea. Y los hallazgos ecográficos fueron lesiones macroscópicas de ecotextura, muy heterogéneas. Se realizaron exámenes citológicos e histopatológicos para el diagnóstico definitivo. El presente informe tiene como objetivo describir los hallazgos radiográficos y ecográficos del fibrosarcoma en la extremidad torácica de tres gatos.

Decortication, thoracic omentalization, and pericardiectomy for treatment of severe fibrosing pleuritis in a cat.

CASE DESCRIPTION: A 5-year-old spayed female domestic shorthair cat was evaluated because of an acute onset of dyspnea and open-mouthed breathing. CLINICAL FINDINGS: Thoracic radiography revealed pleural effusion and signs consistent with restrictive pleuritis, and results of preoperative CT were consistent with diffuse, severe restrictive pleuritis, bilateral pleural effusion, and pulmonary atelectasis. Thoracocentesis yielded a red, turbid fluid that was identified as chylous effusion with chronic inflammation. TREATMENT AND OUTCOME: Exploratory thoracotomy revealed diffuse, severe fibrous adhesions between the mediastinum, heart, lung lobes, and thoracic wall, with a thick fibrous capsule enveloping all lung lobes. Surgical treatment consisted of complete pleural decortication, pericardiectomy, and thoracic omentalization. The cat remained hospitalized for 6 days, receiving oxygen supplementation, multimodal analgesia, and supportive care. Long-term home care consisted of prednisolone administration, rutin supplementation, and provision of a low-fat diet. At recheck examinations 3-, 7-, and 20-weeks postoperatively, the cat remained tachypneic, but was otherwise clinically normal without dyspnea or respiratory distress. Follow-up thoracic radiography revealed improved pulmonary expansion, decreased pleural effusion, and resolved pneumothorax. CLINICAL RELEVANCE: Surgical management of fibrosing pleuritis secondary to idiopathic chylothorax in cats has historically resulted in poor outcomes. This report details the first successful use of complete decortication in the surgical management of severe fibrosing pleuritis in a cat.