Swelling in the right foot is considered to be a precursor of the following diseases: first of all, poorly functioning veins of the lower extremities or varicose veins may cause swelling in the right foot. Also if acute thrombosis of the veins of the right lower extremity occurs, it may also cause swelling in the right foot due to obstruction of venous return. Second, some patients may have gout attacks and increased blood uric acid, which may also cause unilateral foot or ankle swelling and discomfort. If there is bilateral swelling of the lower extremities, it may be related to heart failure and bruising of the body circulation.