3 causes:
presinusoidal (PV/Splenic V thrombosis)
sinusoidal (cirrhosis, tumor, etc)
post-sinusoidal (RHF, constrictive pericarditis, Budd-Chiari)
Imaging manifestations:
Ascites
Splenomegaly (>13 cm length, >6 cm width)
Varices (paraumbilical, paraesophageal, abdominal wall, perisplenic, perigastric, omental)
Mesenteric edema (increased fat attenuation)
Dilated mesenteric veins (PV > 13 mm)
Slow/reverse flow in PV on US (<15 cm/sec; biphasic/completely reversed)
Portal gastropathy, enteropathy, colopathy
GB wall thickening
Enlarged tortuous hepatic artery
Portosystemic shunts