Shifting dullness is a common clinical method to check for the presence of fluid in the abdominal cavity. The principle is that when more fluid accumulates in the abdominal cavity (about 1000ml or more), when the patient is percussed in the supine position, the fluid accumulates in the low part of the abdominal cavity due to gravity, and the intestinal tube containing gas floats on it, so the percussion shows a drum sound in the middle of the abdomen and a turbid sound on both sides of the abdomen. Positive mobile turbid sounds indicate the presence of fluid accumulation in the abdomen. 1, plasma colloid osmotic pressure decreased plasma albumin is lower than 25g/L or accompanied by portal hypertension, fluid is easy to leak from capillaries into the tissue interstices and the abdominal cavity, if water leaks into the abdominal cavity, ascites is formed. This condition is seen in severe hepatic insufficiency, middle to late stage cirrhosis (protein synthesis is reduced), nutritional deficiency (protein intake is insufficient), nephrotic syndrome and protein-losing enteropathy. 2. Sodium and water retention Commonly seen in cardiac and renal insufficiency and moderate to advanced cirrhosis with secondary aldosteronism. In cirrhosis and right heart failure, the reduced activity of natriuretic factor increases sodium reabsorption in the proximal tubule of the kidney. In recent years, it is believed that the mechanism of sodium reabsorption in the proximal tubule is more important than the action of aldosterone in the distal tubule. 3, endocrine disorders In cirrhosis or hepatic insufficiency, the liver degradation function is reduced. On the one hand, the inactivation of antidiuretic hormone and aldosterone decreases, resulting in sodium and water retention; on the other hand, the concentration of some vasodilating vasoactive substances in the blood circulation increases, and these substances cause the peripheral and visceral small artery resistance to decrease, the cardiac output increases, and the viscera are in a high power circulation. Due to the dilatation of visceral blood vessels and visceral stasis, the effective circulating blood volume is relatively insufficient and hypotensive, and the body compensates by releasing angiotensin II and norepinephrine to maintain blood pressure. This is due to reflex excitation of the sympathetic nervous system to release some vasoconstrictive substances, resulting in reduced renal blood flow and decreased glomerular filtration rate.