Retroaortic left renal vein: Multidetector computed tomography angiography findings and its clinical importance

Purpose: To evaluate the appearance, type, frequency, and clinical importance of retroaortic left renal vein (RLRV) in patients examined with multidetector computed tomography (MDCT) angiography. Material and Methods: A total of 1856 patients who underwent CT with urological symptoms (hematuria, flank and abdominal pain, left gonadal vein varicocele) (n = 889) or with symptoms other than urological ones (n = 967) were prospectively evaluated for the presence of RLRV. CT was performed with 110 ml of iodinated contrast material through the antecubital vein at a rate of 3.5 ml/s. Late arterial and early venous phase volumetric data sets were acquired at 30 and 65 s, respectively, from the start of the intravenous injection of contrast medium. In addition to axial images, multiplanar reconstructions (MPR), maximum-intensity projection (MIP), and three-dimensional volume-rendering (3D VR) images were used to assess left renal vein anomalies. Left renal vein anomalies were classified into four types according to their appearance: I) RLRV joining the inferior vena cava (IVC) in the orthotopic position; II) RLRV joining the IVC at level L4-L5; III) circumaortic or collar left renal vein; IV) RLRV joining the left common iliac vein. Results: RLRV was detected in 68 (3.6%) of the 1856 patients, with 26, 22, 17, and three of types I, II, III, and IV, respectively. Forty-four of the 68 patients with RLRV (65%) were in the group with urological symptoms, while 24 patients (35%) were in the group without urological symptoms. Compression of the RLRV was found in 16 patients in the urological symptoms group, while compression was detected in only three patients in the other group. This difference was statistically significant (P < 0.05). The most common urological symptom was hematuria. The frequency of urological symptoms was higher in groups II and IV compared to the other groups. Conclusion: MDCT angiography with axial, MPR, MIP, and 3D VR images is effective in the detection of vascular renal anomalies such as RLRV. Diagnosing RLRV and differentiating it from other pathologic conditions causing hematuria is important in order to avoid complications during retroperitoneal surgery or interventional procedures.