Disorders Of Water Imbalance

Disorders associated with an imbalance in the body fluids are edema, dehydration and water intoxication.

Edema is an abnormal accumulation of extracellular fluid within the interstitial spaces. It results from a number of factors such as increased capillary permeability, obstructions in lymphatic vessels, decrease in the plasma protein concentration as well as increased venous pressure.

Increased capillary permeability result from an inflammation reaction that occurs in response to tissue damage. It usually involves the release of chemicals such as histamine, from damaged cells. Histamine causes an increase in capillary permeability, allowing excessive amounts of fluid to leak out of the capillary into the interstitial spaces.

A number of surgical procedures or parasitic infections that inhibit lymphatic vessels may lead to obstructions in lymphatic vessels. Consequently, back pressure develops in the lymphatic vessels and interferes with the normal movement of tissue fluid into the vessels. Simultaneously, proteins that are primarily removed by lymphatic circulation tend to accumulate in the interstitial spaces, causing the osmotic pressure of the interstitial fluid to rise, and this effect causes still more fluid to be attracted into the interstitial spaces.

Certain health conditions lead to decrease in plasma protein concentration. They include starvation, in which case ingestion of amino acids is insufficient to support the synthesis of plasma proteins. Also, liver diseases may cause failure of the body to synthesize plasma proteins; in glomerulonephritis (kidney disease), the glomerular capillaries are damaged, allowing protein to escape into the urine.

Venous pressure within the liver and portal blood vessels increases greatly, when the out flow of blood from the liver into the vena cava is blocked. As a result, fluid with a high concentration of protein tends to escape from the surfaces of the liver and intestine into the peritoneal cavity resulting in rise in the osmotic pressure of the abdominal fluid, which in turn, attracts more water into the peritoneal cavity by osmosis. This condition called ascites, is characterized by an uncomfortable distension of the abdomen.

Dehydration is a condition of deficiency of body fluid due to an increased output of water that exceeds the intake. It may occur following excessive sweating, or as a result of prolonged water deprivation accompanied by continued water output. In either case, as water is lost, the extra cellular fluid becomes increasingly more concentrated, and water tends to leave the cells by osmosis. It may also accompany illnesses in which excessive fluids are lost as a result of prolonged vomiting or diarrhea. During dehydration, the skin and mucous membranes of the mouth feel dry, and body weight is lost. Also a high fever may develop due ineffective temperature - regulation mechanism caused by lack of water needed for sweating.  In severe cases, as waste products accumulate in the extracellular fluids, symptoms of cerebral disturbances, including mental confusion, delirium and coma, may develop. Infants are more likely to become dehydrated than adults because the kidneys of infants are less able to conserve water than those of adults.  Likewise, the elderly people are also susceptible to developing water imbalances because age, and physical disabilities may make it difficult for them to obtain adequate fluids. The treatment of dehydration involves replacing the lost water and electrolytes. It is important to note that if the water alone is replaced, and this may produce a condition called water intoxication.

Water intoxication may develop in a person who drinks water for a prolonged period faster than the kidneys can excrete the excess in which case the extracellular fluids becomes hypotonic. In another instance, if water alone is replaced in a dehydrated person, the extracellular fluid will become more dilute than normal. In either instances, as the water is absorbed the extra cellular fluid becomes hypotonic to the cells. Then the cells tend to swell as water enters them in abnormal quantities by osmosis.

The symptoms of water intoxication are related mainly to a decrease in the extracellular sodium ion concentration, and they include painful muscular concentration, and coma associated with the swelling of brain tissues. Treatment of this condition usually involves restricting water intake and administering hypertonic salt solutions.