A thrombus is found in a soleal vein, a bit proximal to mid calf. If this were to propagate, it would next involve:

The presence of a thrombus in the soleal vein indicates that it is located within the deep venous system, specifically in the calf region. If this thrombus were to propagate, it would move toward the larger venous structures that drain this area.

The soleal veins drain directly into the posterior tibial veins, which are major deep veins responsible for collecting blood from the posterior part of the calf. Therefore, if the thrombus were to extend from the soleal vein, the most logical next step would be for it to involve the posterior tibial veins, as they are the immediate larger vessels downstream.

The other veins mentioned—anterior tibial veins, popliteal vein, and great saphenous vein—either do not directly connect to the soleal veins in the same way or represent a subsequent area of involvement that would not be the next logical step in propagation. The anterior tibial veins are located more anteriorly and drain a different compartment. The popliteal vein is further proximal and would not be directly involved immediately, and the great saphenous vein is part of the superficial venous system, making it less likely to be involved right after a thrombus in a deep vein like the soleal vein