Hyperdense crescent in a patient with AAA (impending rupture)

Case contributed by Dr Maxime St-Amant

Presentation

Abdominal pain. R/o AAA rupture. Haemodynamically stable.

Patient Data

Age: 90
Gender: Female

CT-scan shows a complex aortic aneurysm (trilobulated abdominal aortic aneurysm with distal thoracic aneurysm) involving both the thoracic and abdominal aorta. There is an important right iliac aneurysm. In the most distal lobulation of the abdominal aneurysm, there is a hyperdense crescent associated with posterior linear fat stranding. The hyperdense crescent is easier to see on the NECT with the modified window. There is no sign of rupture. However, these findings are highly suggestive of impending rupture.

There is an obstruction of the small intestine involving the jejunum at the midline. The zone of transition is located right behind the umbilicus, near a laparascopy trocart site. The findings are compatible with a small bowel obstruction secondary to a post-operative adhesion. There is some free fluid surrounding the small bowel, but none of it has a hemorrhagic density on CT, with perihepatosplenic free fluid. Bilateral pleural effusion.

Two days later, the patient presented hypotension, tachycardia, and intense abdominal pain. 

There is an acute rupture of the known AAA with extensive left > right retroperitoneal hemorrhage, two days following the first CT-scan. The site of rupture is located on the right side of the inferior most lobulation of the aneurysm, near the hyperdense crescent that was described before.

The small bowel obstruction, however, has resolved.

Extensive soft tissue edema related to cardiorespiratory reanimation and fluid administration (anasarca).

Case Discussion

The hyperdense crescent sign in aortic aneurysm is a sign of impending rupture. The aneurysm may or may not rupture in a short course following the diagnosis, depending on multiple factors, but most importantly the size of the aneurysm. 

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Case information

rID: 19233
Case created: 19th Aug 2012
Last edited: 3rd Feb 2016
Inclusion in quiz mode: Included

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