Posterior "Nutcracker" phenomenon in a patient with abdominal aortic aneurysm.

We report on a posterior "nutcracker" phenomenon due to an abdominal aortic aneurysm in a patient with a retro-aortic left renal vein. A 71-year-old man with a known abdominal aortic aneurysm presented in the emergency room with mild hematuria and flank pain. Computed tomography angiography revealed an aortic aneurysm, which compressed the left renal vein between the aorta and the vertebral column. Compression of the left renal vein, due to the aorta with consecutive congestion and hematuria as well as flank pain, was previously described as nutcracker phenomenon. In case of a retro-aortic left renal vein, increase of the aortic diameter can lead to compression of the renal vein and furthermore to the classical signs and symptoms of the "nutcracker" phenomenon, even though the aneurysm is not ruptured or there are no aorto-caval or aorto-left renal vein fistulas.