Rupture of abdominal aortic aneurysm into I.V.C

Clinical History

A 51-year-old obese man presented in our hospital with vague abdominal pain and mild dyspnoea.

Imaging Findings

Laboratory tests showed a drop in Hct value (29, 4). Plain film of abdomen (not available, CT scanogram is shown in Fig.1) was indicative of a large aortic aneurysm. US demonstrated an abdominal aortic aneurysm with a suspected rupture (Fig. 2) but no fluid in neighbouring spaces. CT study was then performed:
Pre contrast images revealed a large (10x10cm) infrarenal aortic aneurysm with mural (fresh) thrombus (Fig. 3).
Post contrast findings: There were primary and secondary signs.
Primary signs included direct visualisation (opacification) of the site of communication between aortic aneurysm and IVC (Fig. 4).
Secondary signs (visible in arterial phase): a. cephalad to the site of communication there was almost synchronous enhancement of aorta and IVC (Fig. 5), because the communication acts like a large A-V fistula, which leads to deviation of enhanced blood from A to IVC (this may explain dyspnoea) and b. distal to the site of communication IVC remains -as expected-unenhanced (Fig. 6).

Discussion

An aortic aneurysm represents a permanent dilatation of the aortic wall. In case of rupture it usually occurs in retroperitoneal space. A rare complication is rupture into IVC with development of an aortocaval fistula (less than 1% of all ruptured abdominal aortic aneurysms). Aortography allows direct identification of the aortocaval fistula and the lumen of the aneurysm. However, it is more invasive than CT and usually is performed if CT is inconclusive or more detailed preoperative assessment is needed. On the other side, US-triplex may be inconclusive, because of the status of the patient and/or obscuration of the US window by fat (like in our case).
CT can accurately show the size and extend of an aneurysm, the abnormal communication between Ao and IVC and its relationships to the other anatomic structures, so, in many institutions CT is the imaging procedure of choice, because of a diagnostic accuracy comparable with aortography, wide availability and ease of performance.

Differential Diagnosis List

Final Diagnosis

Ruptured infrarenal aortic aneurysm into I.V.C and development of an aortocaval fistula.

URL:	https://www.eurorad.org/case/10055
DOI:	10.1594/EURORAD/CASE.10055
ISSN:	1563-4086