Teaching Case

82 year-old male patient with a history of hypertension and arthrosis, presented with back pain.  An ambulatory spinal MRI showed lumbar degenerative disc disease and incidentally an aneurysmatic dilatation of the abdominal aorta of 5 cm.
One week later the patient referred an acute onset of abdominal pain with dorsal irradiation together with pain and palsy of the lower extremities and hemodynamical instability.

A CT angiography performed in the ER department showed:

• An aneurysm of the distal descending thoracic aorta (diameter of 8,5 cm and length of 8,7cm) with a large mural thrombus.
• A type B aortic dissection starting as an intimal tear at the distal end of the thoracic aneurysm and extending into both femoral arteries.
• False lumen thrombosis ascending from the femoral and iliac arteries to the proximal neck of an infrarenal aortic aneurysm (diameter of 6 cm).
• The celiac trunk, superior mesenteric and renal arteries originated in the patent suprarenal false lumen but were permeable.
• The thrombosed false lumen of the infrarenal aneurysm compressed and occluded the true lumen (causing a secondary acute Leriche syndrome).
• Partial re permeabilization from the deep inferior epigastric and median sacral arteries was detected as late staining of the true lumen of the external iliac arteries.

A. Background

The main diagnosis was acute Leriche syndrome secondary to thrombosis of the false lumen in a type B aortic dissection.

Reviewing the literature, we did not find any similar case where a thrombosed false lumen in an aortic dissection was causing an aortoiliac occlusive disease. [1]

B. Clinical perspective

More than one-third of patients with aortic dissection show symptoms and signs indicative of systemic involvement. [2]

Ischemic of the visceral circulation is the main prognostic factor in acute type B dissection. In this case, the celiac trunk, mesenteric and renal arteries were patent, without signs or symptoms of abdominal ischemia, and a successful revascularisation was possible.

Although the main cause of Leriche syndrome is atherosclerosis, especially when an acute onset as this case, other occlusive causes should be taken into account.

C. Imaging perspective

CT is the gold standard imaging technique for immediate diagnosis of acute aortic diseases, allowing a prompt treatment and improved outcome of these life-threatening conditions. [3]

The protocol should include non-enhanced and enhanced CT in arterial and venous phases.

Our CT showed a thoracic aorta aneurysm with an inner thrombus and contrast extravasation in the centre, suggestive of ulceration versus inner bleeding (image 1; blue arrow).

At the distal end of this aneurysm, an intimal disruption of 1,95cm² was seen (green arrow in figure 2) that extended until the external iliac arteries causing a type B aortic dissection, associated to ascendent thrombosis of the false lumen from the iliac (green star) to the proximal neck of the infrarrenal abdominal aortic aneurysm (image 3; yellow arrow).

Compressive effect of the thrombosed false lumen caused aortoiliac occlusion. A late staining of the iliac arteries could be seen (image 4), with re permeabilisation through the deep inferior epigastric and median sacral arteries.

D. Outcome

An emergent surgery of axilo-bifemoral bypass was performed in order to revascularize the inferior extremities, with successful outcome (image 6; red arrow indicates revascularization of common and external iliac arteries after treatment) compared to reconstruction pre-treatment (figure 5). The patient is now asymptomatic.

Extension of a type B dissection into the iliac or femoral arteries has implications for management, especially when percutaneous intervention is being considered. In our case this option was not possible since there was a thrombosis of the false lumen so surgical bypass was preferred. [1][2]

E. Take home message

Aortic dissection is the most common acute emergency condition of the aorta and often has a fatal outcome. Imaging techniques are essential for a correct emergent approach.

Written informed patient consent for publication has been obtained.