Teaching Case

An 80-year-old male patient with history of chronic renal failure was admitted to the emergency department due to anuria, incessant lumbar pain, lower limb swelling, and paraesthesia.

At admission, the patient was haemodynamically stable. On physical examination, a pulsatile epigastric mass was palpable, suggestive of an abdominal aortic aneurysm.

An abdominal ultrasound showed signs of severe chronic kidney disease but no urinary tract obstruction. Additionally, a huge infrarenal aortic aneurysm was visible.

In order to discard complication, an abdominal CT in arterial phase was performed, disclosing the presence of a partially thrombosed infrarenal aortic aneurysm (9 cm of maximum transverse diameter). Furthermore, similar opacification of the inferior vena cava (IVC) to that of the aorta was visible, suggesting fistulisation between this two structures. Direct communication between the two vascular lumens through an ulcer of a mural thrombus in the right wall of the aorta confirmed the suspicion.

Permeability of the deep venous system could not be fully assessed in the absence of a venous phase, however no indirect signs of mesenteric vein thrombosis (bowel mural thickening) were visible. Furthermore, an ultrasound confirmed permeability of the lower limb venous system.

No signs of aneurysm rupture into the retroperitoneum were visible.

Rupture of an abdominal aortic aneurysm into the inferior vena cava is an uncommon and devastating condition, involving less than 5% of cases of aneurysmatic aortic rupture.

A clinical diagnosis is sometimes difficult because the classic diagnostic signs (pulsatile abdominal mass with bruit, acute venous congestion and low back pain) may be absent in many cases [1, 2]. Additionally, aortocaval fistula can debut with or without rupture into the abdominal cavity. In some cases the clinical presentation can lead to confusion, mimicking other cardiovascular conditions such as congestive heart failure, causing lower extremity oedema and paraesthesia [2]. Therefore, acknowledgement of this disease is essential for an early diagnosis and treatment.

Acute renal failure due to shock state or venous hypertension has been widely described. Interstitial renal oedema in venous hypertension may cause a rapid renal function decrease [3], often associated with haematuria. Other atypical forms of presentation may be paradoxical pulmonary embolism from an aortic thrombus, or angina due to increased myocardial oxygen demand, following the spontaneous rupture of the aneurysm [4].

Conventionally, treatment has been open surgical repair with its attendant complications, including a mortality rate of up to 30%. In our patient, endovascular aneurysm repair (EVAR) managed to exclude the fistula [5].