Blood leaving the veins is the clinical manifestation of crush syndrome. Crush syndrome is a series of pathological changes in the body caused after a person is crushed by a stone and earth, especially a muscular limb is crushed for more than one hour (e.g. thigh). Due to the damage to the skin and flesh, blood leaving the vasculature, stasis of blood and Qi, and meridian occlusion, localized pain, swelling of the limb, indentation and hardening of the skin, subcutaneous stasis of blood, and increased skin tension. How to diagnose blood leaving the vasculature? Those who die a short time after crush injury are often in cardiac arrest due to traumatic hemorrhagic shock or hyperkalemia; while those who die after several days are often in renal failure or multi-organ failure due to crush injury. Therefore, in the forensic autopsy work, if the cause of death is highly suspected of extrusion syndrome, the kidney must be taken for pathological examination and confirmation to prevent misdiagnosis. 1, local symptoms Due to the damage of flesh and skin, blood leaving the veins, blood stasis, stagnation of Qi and blood, meridian occlusion, local pain, swelling of the limb, indentation and hardening of the skin, subcutaneous stasis of blood, increased skin tension, and blister formation around the compressed skin. When examining the state of blood circulation in the limb, it is worth noting that if the pulse at the distal end of the limb does not diminish, there is still a risk of ischemic necrosis of the muscle tissue. It is important to check the muscle and nerve function of the limb. Active activity and passive pulling can cause pain, which is helpful to determine the muscle groups in the fascial interval area that are involved. 2. Systemic symptoms Due to internal injury to qi and blood, meridians and internal organs, patients may experience dizziness and dullness of head and eyes, loss of appetite, lack of color, chest tightness and abdominal distension, and constipation. Accumulated stasis and heat may manifest as fever, red face, yellow urine, red tongue, yellow greasy coating, and frequent pulse. In severe cases, palpitations, shortness of breath, or even pale face, cold extremities, sweating like oil and other symptoms (shock). The main features of the extrusion syndrome are as follows: ① shock: some casualties may not appear shock in the early stage, or shock period is short and not found. Some casualties due to crush injuries strong nerve stimulation, extensive tissue destruction, a large amount of blood volume loss, can quickly produce shock, and constantly aggravated. ② myoglobinuria: This is an important condition for the diagnosis of crush syndrome. Myoglobinuria should be considered when a casualty develops brown urine or self-reported hematuria within 24 hours of decompression of the injured limb. The concentration of myoglobinuria in blood and urine peaks 3 to 12 hours after decompression of the injured limb, then gradually decreases and can turn clear on its own after 1 to 2 days. (iii) Hyperkalemia: Because of muscle necrosis, a large amount of intracellular potassium enters the circulation, and because of the difficulty of potassium excretion in renal failure, blood potassium can rise by 2 mmol/L daily during the oliguric phase, even to fatal levels within 24 hours. High blood potassium is accompanied by high blood phosphorus, high blood magnesium and low blood calcium, which can aggravate the inhibitory and toxic effects of potassium on the heart muscle. Acidosis and azotemia: After muscle ischemia and necrosis, a large amount of phosphate, sulfate and other acidic substances will be released, which will lower the pH of body fluid and cause metabolic acidosis. After severe trauma, tissue catabolism and metabolism are exuberant, a large number of intermediate metabolites accumulate in the body, and non-protein nitrogen rises rapidly, which can lead to clinical confusion, deep breathing, irritability and thirst, nausea and a series of manifestations such as acidosis and uremia. If the specific gravity of urine is lower than 1.018, it is the main indicator for diagnosis.