What Causes Feeling Of A Swollen Vein On Left Side Of Abdomen?

Recently, for past 5-10 days, I am feeling a vein has swollen in the left side of my abdomen. It started from there but can feel it now even in the left side of my ribs. When I raise my left hand, I feel like scratching the area by that swollen vein. I, initially, thought it to be some kind of scar in the skin. But when I checked it by rotating my hand around the area, I felt the swollen vein. I am a man 44 years of age. Sometimes, I also feel in my left leg, some vein twitching and giving me intense pain. The leg related pain occurs when I am sleeping with my right leg on top of m left leg. What could be causing my vein in the abdomen and the ribs area to enlarge. Looks it is the same vein that began swelling in the abdomen and then extended to the ribs area.