1.”You can’t urinate but can’t get it out”：The reason is urethral injury, bladder injury, which causes difficulty in urination or even urinary retention. Adult urethral injuries are mostly in the urethral membrane, often combined with pelvic fractures, requiring urology and orthopedics to deal with. It is worth paying attention to the pediatric urethral injury is relatively special, due to the prostate and the surrounding ligament development is not yet perfect, the site of urethral injury is often located in the urethro-prostatic department, the treatment is not timely, will cause the injury of distal urethral fibrosis and regression, scar formation, subsequent repair effect is poor, early surgical intervention should be carried out. Spinal cord injury can also cause urinary retention, need to catheterize as soon as possible, to avoid the bladder forcing muscle impact. 2, “little or no urine”: unlike urinary retention, little or no urine of the casualty, the bladder is empty, not the bladder or urethra problems, but the kidney failure, little or no urine production, known as the “squeeze syndrome”, the underlying causes are Muscle damage to the limbs. According to statistics, the mortality rate of patients with crush injuries in the 1995 Kobe earthquake in Japan was 13.4%, and in the 7.8 magnitude earthquake in Tangshan, China in 1976, the death and injury rate caused by crush syndrome accounted for 20% of the total. In the Wenchuan earthquake, crush injuries and crush syndrome remained one of the leading causes of death and injury. The reason for this is that the compression of the limbs by collapsed buildings during the earthquake, direct injury and sustained ischemia caused a large number of skeletal muscle cells to lyse, and a large number of intracellular substances (potassium, phosphorus, purine, lactic acid, coagulation kinase, creatine kinase, myoglobin, etc.) to be leaked, and at the same time, the inflammatory mediators released caused platelet aggregation, vasoconstriction, vascular leakage, and exacerbation of edema and hypoperfusion, forming a vicious cycle. Once rescue is obtained, compression is lifted, and blood is perfused to the ischemic site, severe blood volume deficiency occurs at other sites and hypovolemic shock occurs. Large amounts of excreted intracellular material such as myoglobin rapidly enter the circulation. Myoglobin and detached necrotic tubular epithelial cells, etc. block the renal distal tubules and collecting ducts, which, together with hypovolemia, causes a dramatic decrease in renal perfusion and eventually triggers acute renal failure.