Anaesthetic Challenges During Colonoscopy-Induced Intestinal Perforation in a Cat

While colonoscopies are generally benign procedures, rare complications such as colonic perforation may result in life-threatening consequences. A 15-year-old neutered male British Shorthair cat underwent colonoscopy for investigation of chronic gastrointestinal signs and persistent tenesmus. During endoscopic evaluation of a distal colonic stricture, the cat developed sudden tachycardia, severe hypoxaemia, and a dramatic decline in end-tidal carbon dioxide (EtCO₂), accompanied by diffuse subcutaneous emphysema. Intestinal perforation was suspected, and venous blood gas analysis revealed a markedly enlarged EtCO₂-PvCO₂ gradient, consistent with severe ventilation-perfusion mismatch and contributing to a presumptive diagnosis of pulmonary air embolism. Anaesthetic management focused on ventilatory adjustments, including an increased respiratory rate and initially high, then moderate peak inspiratory pressures, aimed at reducing EtCO₂ and improving oxygenation. However, improvements in oxygen saturation were limited and the cat was euthanised. Contrast-enhanced post-mortem computed tomography confirmed a distal colonic perforation with extensive air dissemination, including pneumoretroperitoneum, pneumomediastinum, pneumothorax, and subcutaneous emphysema.