Anatomic and hemodynamic evaluation of renal venous flow in varicocele formation using color Doppler sonography with emphasis on renal vein entrapment syndrome

OBJECTIVE: To investigate the anatomic and hemodynamic properties of testicular venous drainage and its effects on varicocele formation and reflux using color Doppler ultrasound (US) with emphasis on renal vein entrapment syndrome. MATERIAL AND METHODS: Upper abdominal and scrotal US examinations of 35 varicocele patients and 35 healthy male subjects were performed in the supine position during rest, during a Valsalva maneuver and in the erect position. The aortomesenteric angle and distance (AMA and AMD, respectively), peak mean velocities (PVs) and diameters of different segments of renal veins, testicular vein diameters and duration of flow inversion were measured. RESULTS: In the varicocele group, the lateral segment of the left renal vein (LRV) had a larger diameter and slower PV, and the medial segment of the LRV had a smaller diameter and faster PV. The diameter of the dominant draining vein correlated with the PV of the medial and lateral segments of the LRV, whereas there was no correlation between the diameter of the dominant draining vein and the diameters of the right renal vein (RRV) and the lateral segment of the LRV or the PV of the RRV. The duration of flow inversion correlated with the diameter and PV of the medial segment of the LRV. No correlation between the diameters and PVs of the RRV and the lateral segment of the LRV was detected. CONCLUSIONS: The decreases in the AMA, AMD, diameter of the medial segment of the LRV and PV of the lateral segment of the LRV, and the increases in the PV of the medial segment of the LRV and the diameter of the lateral segment of the LRV in varicocele patients in all positions suggest the entrapment or impingement of the left renal vein between the aorta and the superior mesenteric artery. This has been defined as the "nutcracker phenomenon", which is known to affect varicocele formation.