Hot spot sign occurs secondary to superior vena cava obstruction and portosystemic venous shunting between the superior vena cava and the left portal vein via the internal mammary and paraumbilical veins along the ligamentum teres.

The focal hepatic hot spot sign can also be seen on the Technetium-99m sulfur colloid scans of the liver and spleen as a focal area of increased radiopharmaceutical uptake in the medial segment of the left hepatic lobe (segment IV).