edema Trasudatizio 60% of the body weight is made up of water (≈ 40L ) , but only 5% of this water is in the blood plasma. Most of the water is then distributed between the cells and interstitium . The term edema is just to indicate an increase in the interstitial fluid . While the inflammatory edema is typically essudatizio , rich in proteins and cells , edema from hemodynamic disturbances is trasudatizio . The transudate is isotonic with plasma, low in protein and devoid of cells and fibrin. Depending on the location of fluid collections distinguish between hydrocephalus , hydrothorax , hydropericardium , idroperitoneo (or ascites) , idroarto , hydrocele ( in the testicle ) and anasarca ( generalized edema ) . The movement of fluid between the vascular and interstitial compartment is governed mainly by the hydrostatic pressure and oncotic pressure inside the vessel. At the head of the arteriolar microcirculation prevailing hydrostatic pressure within the capillary (Pc), therefore, liquid passes from cappillare interstitium. Proceeding towards the head of the venous Pc tends to decline , while the oncotic pressure within the capillary ( σc ) , remains unchanged. Indeed the endothelium , intact , is a semipermeable membrane that prevents the passage of proteins into the interstitium . At the head of venous σc , which draws liquid into the capillary prevails over Pc and , aided by the increase in interstitial hydrostatic pressure (Pi ), for a net reabsorption of fluid. In reality, not all the liquid that comes out is the strength to go back , but thanks to the lymphatic drainage is avoided by the progressive formation of edema. The lymphatics shall also carefully remove traces of albumin , serum protein which , given its size , it is capaca to cross the endothelial barrier . The accumulation of albumin in the interstitium may determine increase oncotic pressure , in the same ( σi ) , and thus favor the formation of edema. Localized edema may therefore depend on: Reduced lymphatic drainage may be due to obstruction of inflammatory or neoplastic (lymphoma ) , lymphatic vessels and lymph nodes. For example, lymphatic filariasis due to extensive fibrosis and lymph node at the level of the groin area , resulting in hydrocele and idroarto ( lower limbs) , a condition identified as elephantiasis . In addition, the treatment of cancer by surgical removal of the tumor and associated lymph nodes , it is often due to severe edema. Increased venous pressure (↑ Pc) may be due to compression of the vessels or the formation of varicose veins, or blood clots . For example vein thrombosis of the lower limb profoda determines unedema limited the affected limb . Systemic edema depend on: Right heart failure or constrictive pericarditis (↑ Pc) heart failure is associated with a reduction in stroke volume and , therefore , to ipopoerfusione failure. This activates the juxtaglomerular system that synthesizes and secretes renin , an enzyme capable of transforming angiotensinogen , produced by the liver , to angiotensin -I. The latter is transformed by ACE, expressed pulmonary endothelium , angiotensin -II induces arteriolar vasoconstriction and aldosterone secretion. The retention of sodium and water , induced by aldosterone , is designed to increase the blood volume to improve the cardiac output, but if the heart , decompensated , is not able to increase the range , the volume increase does no more than aggravate edema. Decreased synthesis of albumin (↓ σc ) may be due to liver failure or protein malnutrition ( kwashiorkor ) . The reduction of the oncotic pressure determines a net shift of fluids to the tissues with consequent reduction of the plasma volume. The renal hypoperfusion , which is perceived by the system causes the juxtaglomerular apparatus renin secretion . As seen above , water retention, will only aggravate the anasarca . Increased renal loss of albumin (↓ σc ) may be due to chronic glomerulonephritis or nephritis tubolointerstiziali . Renal retention of Na + and H2O (↑ Pc) water retention may contribute to various forms of edema, but also can be the primary cause . This condition occurs in case of renal hypoperfusion , heart failure or left renal artery stenosis , ipocatabolismo aldosterone , liver failure , increased secretion of steroid hormones , leading to adenoma or during pregnancy, and finally, oliguria, due to renal failure. Pulmonary edema Trasudatizio is due to cardiogenic pulmonary hypertension , which is due to left heart failure , mitral stenosis or hypervolemia ( fluid retention by renal hypoperfusion ) Essudatizio is due to infection, inhalation of irritant gases or hypoxia ( suffering local causes increased permeability ) Ascites ( idroperitoneo ) in Liver Cirrhosis Edema formation is primarily due to portal hypertension (↑ Pc), resulting in the reduction of runoff and the formation of arteriovenous shunts . Sclerosis will also contribute in reducing lymphatic drainage ( σi ↑ ), while liver failure causes hypoalbuminemia (↓ σc ) and ipocatabolismo aldosterone ( water retention and ↑ Pc) .
Posted on: Mon, 03 Feb 2014 17:16:21 +0000