What effect is this aneurysm having on the left kidney?
It is obstructing it's outflow (hydronephrosis) and compromising its perfusion (combination of hydronephrosis, direct compression and distortion of the renal vessels).
What two factors are most important in predicting likelihood of rupture of an run-of-the-mill AAA?
The risk of rupture is proportional to the size of the aneurysm and the rate of growth. Differing rates of rupture for a given aneurysm size have been reported in the literature but the general consensus is that aneurysms greater than 5.0 cm in women and 5.5 to 6.0 cm in men carry a significantly increased risk of rupture and should be treated. Furthermore, aneurysms that expand greater than 10 mm per year are also at significant risk of rupture and are considered for treatment even when less than 5.0 cm.
In addition of atherosclerosis (which is by far the most common cause of AAA) what are other aetiologies of abdominal aortic aneurysms?
Inflammatory abdominal aortic aneurysm, chronic aortic dissection, vasculitis (e.g. Takayasu arteritis), connective tissue disorders (e.g. Marfan syndrome and Ehlers-Danlos syndrome), mycotic aneurysm.
CT of the abdomen demonstrates a large infrarenal saccular aneurysm of the abdominal aorta projecting towards the left with 81mm in AP diameter with a length of 75mm. Much of the lumen is filled with thrombus, with contrast passing into the thrombus at the superior margin of the aneurysm, in close proximity to the outer wall. Although no contrast extravasation can be identified, extensive hyperdense fluid is present in the retroperitoneum, posterior to the aneurysm.
The left kidney demonstrates hydronephrosis and reduced enhancement of the cortex, with distortion and compression of the renal vessels.