Pulmonary Hypoplasia Associated with Ascites and Hydrothorax in a Newborn Pig

Background: Pulmonary hypoplasia is characterized by incomplete development of the lungs, owing to congenital defectsor the action of toxic substances. Moreover, it has rarely been described in pigs. Ascites or hydroperitoneum is characterized by the presence of fluid inside the abdominal cavity and does not generally cause changes in the abdominal organs. However, hydrothorax, characterized by the presence of fluid within the thoracic cavity, is responsible for the compression of thoracic organs and consequent heart and respiratory failure. This study aims to describe a case of congenital pulmonary hypoplasia associated with ascites and hydrothorax in a newborn pig.Case: A male neonate Landrace pig that died shortly after delivery was presented for necropsy with increased abdominal volume and bilateral extension of the pelvic limbs. The pig belonged to a litter of 13 piglets, four of which died shortly after birth. The rest of the piglets were poorly developed, but only one was presented for necropsy. Significant external changes, along with permanent distension, interpreted as arthrogriposis, were observed in the pelvic limbs. The skin of the ventral abdominal region was thin, with evidence of all blood vessels, interpreted as telangectasis. An internal examination revealed the presence of a slightly yellowish liquid in the thoracic and abdominal cavities, interpreted as hydrothorax and ascites, respectively. The lungs were reduced in size, indicating pulmonary hypoplasia. The liver had rounded edges, which were dark red and firm, with an irregular surface. Significant microscopic findings were observed in the lungs, which were divided by fibrous connective tissue and showed evidence of small and atrophied alveoli. Furthermore, connective tissue was observed around the peribronchiolar regions and underdeveloped cartilage around the airways. The liver showed dilation of the centrilobular veins. Moreover, the sinusoids were filled with erythrocytes, indicating congestion.Discussion: Pulmonary hypoplasia is a rare birth defect in pigs and can be accompanied by malformations of other organs, including anasarca. Pulmonary hypoplasia is caused by conditions that compress the lungs, such as congenital diaphragmatic hernia, intrathoracic masses, and pleural effusion or malformations in the chest cavity. However, none of these conditions were observed in the current case. Instead, the histopathological changes observed in the lungs were characteristic of pulmonary hypoplasia. A microscopic examination revealed that the hypoplastic lungs showed a reduced number of alveoli, replacement of the peribronchiolar smooth muscle by the connective tissue, and underdeveloped cartilage around the airways, all of which are characteristic of pulmonary hypoplasia. Vascular telangiectasia is characterized by abdominal distention due to a marked ascitic condition. Invariably, ascitic fluid accumulation results from changes in hydrodynamic parameters. The hydrothorax observed in this animal was suggestive of changes in the hydrodynamic parameters, which consequently led to fluid accumulation in the chest cavity. This has been previously described in a newborn pig infected with Clostridium difficile. The permanently and bilaterally extended pelvic joints observed at birth in this animal were interpreted as arthrogriposis. This change is attributed to various factors, such as fetal paralysis in pigs that ingest toxic substances like alkaloids present in Conium maculatum and in the stalks of Nicotiana tabacum and Datura stramunium. The literature describes pelvic limb paralysis in Landrace pigs as a genetically inherited disorder. However, it was not possible for us to establish the cause of arthrogriposis for certain in this pig.