Water retention is the decreased excretion of water from blood into urine. Water retention is caused by a variety of conditions including heart, liver and kidney failure. Protein intake is monitored in diseases that cause water retention, since there is increased tendency for its byproducts to accumulate in these conditions.
Protein Metabolism
The breakdown of proteins begins in the stomach as a result of increased production of acid. The acid of the stomach activates the enzyme that breaks down proteins. Proteins are further broken down to amino acids in the small intestine by enzymes released from the pancreas. Amino acids are absorbed and then processed by the liver. The liver also destroys excess proteins by converting them to urea, which is then excreted by the kidneys. Failure of the kidneys to excrete urea -- such as may be the case in renal failure and liver cirrhosis -- causes uremia or excess buildup of urea in the blood. Urea is toxic to the brain.
Liver Disease
The liver is responsible for making several important proteins in the body, including albumin and clotting factors. Albumin is the most abundant protein in the blood; it contributes the osmotic force that attracts water into the blood vessels. In liver cirrhosis, there is decreased production of albumin, which weakens the osmotic force and therefore allows the escape of excess fluid from the blood into the tissues. Liver cirrhosis is also associated with ascites or the accumulation of fluid in the abdomen. Liver cirrhosis also causes renal failure by decreasing blood flow to the kidneys.
Renal Failure
Renal failure can be caused by decreased blood flow to the kidneys, disease of the kidneys or obstruction of urine outflow. Diseases that decrease blood flow to the kidneys include heart failure, liver cirrhosis, excess blood loss and septic shock. Acute pyelonephritis and septicemia may cause damage to the kidneys and reduce their function. Kidney stones can obstruct the flow of urine and, as a result, decrease the excretion of urea.
Management
Decreasing sodium intake can reduce water retention that can lead to liver cirrhosis and heart failure. In liver cirrhosis and heart failure, there is increased retention of sodium which causes the retention of water; decreasing sodium intake lessens water retention. Protein intake should be decreased in the presence of liver cirrhosis, heart failure and renal failure; decreasing protein intake helps to reduce the production of urea, which is toxic to the brain. Dialysis is often necessary in renal failure due to fluid overload, very high potassium and mental status changes.
