Multiple venous thrombi are demonstrated in this case; portal vein thrombus extending to the splenic vein and left renal vein thrombus with fine extension to IVC. 

Portal vein thrombus is common in patients with chronic liver disease rather than the tumor thrombus. Differentiating bland from tumor thrombus is necessary as they have different management and prognosis. The presence of malignancy doesn't exclude the possibility of bland thrombus as shown in this case. Also, both can be co-existing.

Bland thrombus is formed due to the change in hemodynamics in veins adjacent to the tumor by the mass effect of the tumor that displaces or compresses these veins.

On imaging, bland thrombus doesn't enhance and separable from the tumor with no signs of tumor vein invasion. The dilated portomesenteric axis, in this case, is due to portal hypertension and less likely an expansion by the thrombus itself which is a sign of a tumor thrombus. Renal vein thrombus is commoner on the left side than the right, presumably as it is longer.

Diffusion-weighted MRI is helpful adjunctive modality with contrast study. Tumor thrombus show restricted diffusion due to high cellularity, unlike bland thrombus. Bland thrombus generally shows non-restricted diffusion. Yet, it may demonstrate low ADC values due to the high viscosity as well as paramagnetic effects of intracellular deoxyhemoglobin and methemoglobin contents ¹.