Equine Pneumothorax Study Guide

Overview and Clinical Importance

Pneumothorax refers to the presence of air within the pleural space, disrupting the normal negative pressure required for lung expansion. In horses, this condition carries unique clinical significance due to the fenestrated nature of the equine mediastinum, which allows unilateral pneumothorax to potentially become bilateral and life-threatening.

Pneumothorax in horses most commonly occurs secondary to pleuropneumonia (42.5%), open thoracic wounds (22.5%), and closed thoracic trauma (17.5%). In neonatal foals, rib fractures sustained during parturition are a significant cause of pneumothorax and can result in hemothorax, cardiac laceration, and sudden death.

Relevant Anatomy

Equine Thoracic Anatomy

Horses have 18 pairs of ribs, with 8 pairs classified as true (sternal) ribs that attach directly to the sternum via costal cartilage, and 10 pairs of false (asternal) ribs that form the costal arch. The equine thorax is notably longer and larger than in ruminants, providing greater respiratory capacity but also creating unique clinical considerations.