Transient swelling of the hand veins is a normal process due to the location and function of these vessels. Veins are more superficially located than arteries and they carry post-capillary blood from tissues (deoxygenated) back to the heart for reoxygenation in the lungs and distribution through the arteries back to the tissues. Veins have a high capacitance, meaning that they are able to store variable amounts of blood at any given time. They also have one-way valves that prevent the back-flow of blood. The result is the when left in a dependent position for extended periods of time, increased volumes of blood may accumulate in the veins, causing them to dilate and appear swollen. In the hand, they are particularly close to the skin surface and will therefore have increased appearance compared to other parts of the body where they may be deeper and covered by other tissues such as fat. In rare instances, there are conditions in which the return of blood from the arms is obstructed. This can lead to diffuse swelling of the veins and the arm in general and may be associated with skin discoloration and pain. If you are experiencing these other symptoms as well, I recommend that you see your doctor
for further evaluation and treatment if necessary.