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.