Overview
The equine lungs (pulmones) are long and extend caudodorsally under the dome of the diaphragm. The interlobar fissures are shallow, so each lung looks almost like a single piece; the interlobular septa are incomplete and allow some collateral ventilation. The mediastinum is thin and often incomplete, so pleural effusions and pneumothorax are usually bilateral.
Lobes and bronchi
- Left lung: cranial lobe and caudal lobe, separated by the cardiac notch.
- Right lung: cranial lobe, caudal lobe and accessory lobe, which fills the mediastinal recess between the heart and the diaphragm. There is no middle lobe.
- Bronchi: the two principal bronchi arise at the tracheal bifurcation and branch into lobar and segmental bronchi.
- Auscultation and percussion area: the caudal border of the lung field runs roughly from the 16th intercostal space at the level of the tuber coxae, through the 11th at the level of the shoulder joint, to the 6th at the level of the elbow.
Clinical relevance
- Equine asthma: lower airway inflammation linked to inhaled dust and moulds from hay and bedding. The severe form (formerly "recurrent airway obstruction") causes cough, nostril flaring and an abdominal heave line on expiration; the mild form reduces performance.
- Exercise-induced pulmonary haemorrhage: common in racehorses; it mainly affects the caudodorsal regions of the lungs and is diagnosed by endoscopy or bronchoalveolar lavage.
- Pleuropneumonia: associated with long transport with the head tied high; Streptococcus equi subsp. zooepidemicus and anaerobes cause pneumonia and pleural effusion, which is drained by thoracocentesis.
- Rhodococcosis: Rhodococcus equi causes pyogranulomatous bronchopneumonia with abscesses in foals a few months old.
- Examination: ultrasound shows effusion, pleural irregularities and peripheral consolidation; bronchoalveolar lavage gives the lung cytology.