Prevalence of pectus excavatum (PE), pectus carinatum (PC), tracheal hypoplasia, thoracic spine deformities and lateral heart displacement in thoracic radiographs of screw-tailed brachycephalic dogs

RESEARCH ARTICLE Prevalence of pectus excavatum (PE), pectus carinatum (PC), tracheal hypoplasia, thoracic spine deformities and lateral heart displacement in thoracic radiographs of screw-tailed brachycephalic dogs Renata Komsta ID1☯*, Zbigniew Osiński2☯, Piotr Dębiak1‡, Piotr Twardowski1‡, Barbara Lisiak1‡ a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Komsta R, Osiński Z, Dębiak P, Twardowski P, Lisiak B (2019) Prevalence of pectus excavatum (PE), pectus carinatum (PC), tracheal hypoplasia, thoracic spine deformities and lateral heart displacement in thoracic radiographs of screw-tailed brachycephalic dogs. PLoS ONE 14 (10): e0223642. https://doi.org/10.1371/journal. pone.0223642 Editor: Francesco Staffieri, University of Bari, ITALY Received: December 21, 2018 Accepted: September 25, 2019 Published: October 10, 2019 Copyright: © 2019 Komsta et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. 1 Laboratory for Radiology and Ultrasonography Department and Clinic of Animal Surgery, Faculty of Veterinary Medicine, University of Life Science, Lublin, Poland, 2 National Veterinary Research Institute, Puławy, Poland ☯ These authors contributed equally to this work. ‡ These authors also contributed equally to this work. * Abstract Pectus excavatum, thoracic spine deformities, tracheal hypoplasia and lateral heart displacement are frequently described in brachycephalic dog breeds. Pectus carinatum is described sporadically, although the authors’ observations demonstrate that it may occur in certain brachycephalic dog breeds. It was hypothesised that dogs of screw-tailed brachycephalic breeds carry a greater risk of these anomalies than normal-tailed brachycephalic breeds, and that there could a relation between the presence of pectus excavatum or pectus carinatum and thoracic spine deformities, tracheal hypoplasia and lateral heart displacement. During retrospective studies, these anomalies were identified in lateral and dorsoventral radiographs of the thorax in brachycephalic dog breeds. A statistical analysis revealed that the frequency of pectus excavatum occurrence in screw-tailed and normaltailed brachycephalic dog breeds is similar. The greatest risk of pectus excavatum occurrence is carried by two breeds: Maltese (60%) and English Bulldog (58%), while for pectus carinatum: Pug (41%) and French Bulldog (18%). Dogs of screw-tailed brachycephalic breeds carry a greater risk of kyphosis (p < 0.0001), tracheal hypoplasia occurrence (p < 0.0001), compared to "normal-tailed" breeds. The hypothesis concerning a relation between the presence of pectus excavatum or pectus carinatum and the other anomalies studied was not confirmed (p > 0.05). It was demonstrated that in dogs of brachycephalic breeds there was a greater risk of co-incidence between kyphosis of the thoracic spine and lateral heart displacement (p = 0.038), as well as kyphosis of the thoracic spine and tracheal hypoplasia (p = 0.003). Funding: The authors received no specific funding for this work. Competing interests: The authors have declared that no competing interests exist. PLOS ONE | https://doi.org/10.1371/journal.pone.0223642 October 10, 2019 1 / 14 PE, PC, tracheal hypoplasia, thoracic spine deformity, heart displacement in screw-tailed brachycephalic dogs Introduction Pectus excavatum (PE) is an anomaly of the chest wall, characterized by the dorsal deviation of the sternum and associated costal cartilages with subsequent a dorsoventral flattening of the entire thorax [1–7]. PE is classified as a congenital disorder, although in 2012 Kurosawa reported an acquired form of PE in a 13 year old Labrador-Retriever [8]. This disorder is not frequently observed in animals, although it is particularly frequently reported in brachycephalic dog breeds. Pectus carinatum (PC) is characterized by protrusion of the sternum [2, 9]. It is a sporadically reported congenital disorder of the thoracic wall. Both defects may remain symptomless, although PE may lead to severe dyspnoea and abnormalities of the cardiovascular function, while PC may cause transient respiratory distress. Diagnosing PE and PC is based on clinical and radiological examinations [7, 9]. Pectus excavatum and pectus carinatum are also reported in humans, and are believed to be connected with the occurrence of vertebral deformities, in particular with scoliosis [10–12]. Kyphosis and scoliosis also occurs in dogs, in particular in screw-tailed brachycephalic breeds [13, 14]. In animals, PE is frequently found alongside tracheal hypoplasia [1, 4], cardiomegaly, and malposition of the heart [1, 5, 7, 15]. The purpose of this retrospective study was to evaluate the prevalence of PE and PC, thoracic spine deformities, tracheal hypoplasia and lateral heart displacement in lateral and dorsoventral thoracic radiographs in screw-tailed and normal-tailed brachycephalic dog breeds. The authors hypothesised that dogs of screw-tailed brachycephalic breeds carried a greater risk of the occurrence of the above anomalies than normal-tailed brachycephalic dog breeds. Our secondary hypothesis was that there was a statistically significant relation between the presence of PE or PC, and thoracic spine deformities, tracheal hypoplasia and lateral heart displacement. Material and methods Ethics statement In accordance with the Act “On the Protection of Animals Used for Scientific or Educational Purposes” (15/01/2015) this study was considered as sub-threshold for specific ethical approval, as the work involved only the analysis of data routinely recorded from normal and necessary clinical procedures. Cases The digital medical database of the Faculty of Veterinary Medicine at University of Life Sciences in Lublin was retrospectively reviewed from March 2011 and September 2018. The criteria for inclusion in the study were as follows: dogs of selected brachycephalic breeds (English Bulldog (EB), French Bulldog (FB), Pug (Pu), Maltese (Mlt), Cavalier King Charles Spaniel (Cav), Shih Tzu (Sht) and Pekingese (Pkn)) with lateral and dorso-ventral radiographs covering the entire thorax. The criteria for exclusion were as follows: dogs diagnosed with diaphragmatic hernia, a very large volume of unilateral pleural gas/fluid and a pericardial tamponade. For each dog, which met the inclusion criteria, the breed, age, and sex were recorded. These dogs were then assigned to one of two groups, based on their breed: Group A: screw-tailed brachycephalic breeds (n = 68) including EB, FB and Pu [14], and Group B: normal-tailed brachycephalic breeds (n = 56) including Mlt, Cav, Sht, and Pkn. Radiographic assessment Thoracic radiographs were carried out (...truncated)