A 71-year-old male presented with a symptomatic expanding 11 cm infrarenal aortic aneurysm 5 years post-endovascular aortic repair. Duplex ultrasound and angiography showed no identifiable endoleak but confirmed an enlarging aneurysm sac with a new saccular configuration. The ultrasound findings were particularly unusual in that the aneurysm sac was a mixture of hardened echogenic material and an anechoic fluid-like substance, with the echogenic material appearing to float around the sac with gravitational dependence. Open surgical intervention was performed. The aneurysm appeared pressurised with forceful expulsion of the sac contents post-incision, though again no endoleak was identified. The sac contents were confirmed as a mixture of clear fluid and hardened haematoma. At 6 weeks follow-up there was complete return of the aneurysm sac almost to its pre-open surgery state. Multiple endoleak theories were considered from initial imaging through to follow-up.