Hi, I had gone through your question and understand your concerns. Considering his age and symptoms, this my be suggestive of deep vain thrombosis which means that clot is formed inside the big leg vessel. So He needs to do Doppler ultrasound to rule this. Vein thrombosis which is manifested with unilateral swelling of the leg, pain in calf and thigh, lividity of the skin. Some conditions such as, obesity and recent surgery may increase the risk of it. This may be serious if blood clot travels to heart and lungs so it should be ruled out as soon as possible and then appropriate treatment can be started. In most cases it include strict resting heparin infusions and aspirin. More invasive procedures are rarely required. Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate in writing to us. I will be happy to answer your questions. Wishing you good health.