Spontaneous ruptured iliac artery aneurysm causing acute secondary AV fistula

A 73-year-old woman presented with a 6-hour history of sudden onset lower abdominal pain. Her comorbidities included chronic obstructive pulmonary disease and hypertension. She was under surveillance for a known thoracoabdominal aneurysm. On presentation, she was hypotensive with a systolic blood pressure of 50 mm Hg and a pulse of 60 beats per minute. On examination, she had a pulsatile mass with bruit in her right lower abdomen. Pedal pulses were palpable in both feet. Blood gas analysis revealed a metabolic acidosis with a pH of 7.21 and a lactate of 7.1. Haemoglobin remained stable between 90-100 g/dL. Her other routine blood tests were unremarkable, and blood cultures were negative. Imaging showed a ruptured right common iliac artery aneurysm into the right common iliac vein with secondary arteriovenous fistula communication. Surgical intervention was discussed with the patient but due to her frailty, it was deemed not in the patient's best interests.