According to WebMD, the first symptom of a blood clot inside the calf, also known as a deep vein thrombosis, varies from person to person. Common symptoms include calf pain, weakness, swelling or the appearance of bulging surface veins. Deep vein thrombosis can also be present without any symptoms. This is dangerous, because the blood clot can break free and travel to block more critical blood vessels.
WebMD advises paying particular attention to any signs of deep vein thrombosis if the patient is over 60 years old, a smoker, is overweight or sits for long periods of time. These blood clots can cause chronic pain and swelling in the lower leg and can damage veins, permanently decreasing their function. If the blood clot breaks free, it could travel to major organs, such as the lungs or heart, causing a life-threatening condition.
WebMD states that diagnosis involves imaging scans; X-rays, ultrasound or magnetic resonance imaging are able to reveal the presence of the blood clot. Many conditions can cause the symptoms of deep vein thrombosis, so several tests are performed. Treatment can involve the use of anticoagulant medications or, in severe cases, surgeries to remove the clot or protect the major organs from the danger of a clot breaking free.
While a pulmonary embolism is the most significant complication of deep vein thrombosis, it isn't the only one, notes Mayo Clinic. Postphlebitic syndrome occurs after a blood clot due to damage to the vein from the clot itself. It may not occur for several years after the clot resolves, or it may appear right away. Symptoms include swelling, skin discoloration, pain and skin sores.