varicocele

Line diagram of a typical bidirectional Doppler recording of a stop-type varicocele (red) in which flow is stopped by a competent valve in the pampiniform plexus above the level of communicating veins. The shunt-type of varicocele is depicted in blue. Because the valves in the pampiniform plexus contiguous to the testicular veins are incompetent or absent, venous flow is shunted via communicating veins into orthograde draining veins; these are shown to represent deferential and cremasteric veins at contrast venography.


http://emedicine.medscape.com/article/382288-overview