Water is a major requirement of living organisms. Biochemical life processes within the cells and tissues of the body require the presence of water. In fact, the majority of the bulk of the human body (about 60%) is composed of water. However, too much water can also cause health problems.
How does fluid overload occur?
An excess of water in the body can occur due to two main reasons: (1) an excessive intake of water beyond the needs of the body, and (2) the inability of the body to expel the water that is present in excess. The second reason is the usual cause of fluid overload in the body. The presence of excess fluid in the body is also referred to as fluid overload.
Medically, such a condition is referred to as hypervolemia, which means “excessive blood”. A large quantity of fluid in the body resides in extracellular compartments, such as blood and tissue spaces. The kidneys play a major role in regulating the volume of fluid in the body. They do this by regulating the volume of urine production.
For example, when the volume of fluid in the body falls below the normal level, urine production slows down. Conversely, when the fluid in the body is present in excess, urine production increases. The antidiuretic hormone (also known as vasopressin) secreted by the hypothalamus in the brain plays a critical role in maintaining the fluid homeostasis by controlling urine production by the kidneys.
Other routes of fluid loss from the body are through sweat, exhaled air from the lungs, and stools. These are minor routes of fluid loss. However, these routes may become significant in certain conditions such as hot and humid climates that cause profuse sweating and diarrheal diseases. Vomiting may also cause significant fluid loss, especially when accompanied by diarrhea.
Read more on effusion.
What is hypervolemia?
When the rate of fluid intake is greater than the rate of fluid loss, hypervolemia may occur. The resultant accumulation of excess fluid in tissue spaces and blood can cause a variety of adverse effects, including death. Hypervolemia is usually a gradual process that doesn’t cause fatality immediately. However, any concerns of fluid accumulation in the body should prompt a medical investigation. Affected individuals should not try to self-medicate with diuretic pills or decrease their fluid intake without consulting a doctor.
Causes of Hypervolemia
Water in present in many different forms within the body. Water is a major constituent of blood, tissue fluid, and cytoplasm within the cells. Water may not always exist in liquid form within the body. Some of the water in the body is bound to other molecules.
The fluid compartments within the body are not composed solely of water. Many solutes (such as electrolytes and proteins) are also present within the body fluids. The concentration of these solutes between different fluid compartments determine the direction of flow of fluid from one compartment to another. Therefore, excessive fluid within a compartment may result from the presence of excessive solutes within that compartment.
Sodium is one of the most important electrolytes in the body that influences the movement of water from one tissue compartment to another. Water flows from compartments with less sodium to compartments with more sodium. Therefore, the human body regulates the concentration of sodium in various tissue compartments in order to maintain water homeostasis.
The following are the general mechanisms through which fluid overload or hypervolemia may occur within the body:
Excessive intake: Excessive intake of water or electrolytes could lead to hypervolemia. Common routes through which excessive intake might occur include blood or other fluid transfusions and intravenous therapy. Consumption of excessive sodium (through a high salt diet) may also lead to hypervolemia.
Excessive retention: A variety of diseases can lead to excessive retention of fluid and electrolytes within the body. Examples of such diseases include congestive heart failure, renal diseases, liver diseases, and hormonal disturbances. Low protein diets may also lead to excessive retention of fluid within the body.
Changes in solute concentrations: Changes in solute concentrations within tissue compartments may occur due to administration of hypertonic solutions and blood proteins. Such changes could occur during treatment of burns.
Signs and Symptoms of Fluid Overload
Fluid overload occurs over a period of time. Signs of hypervolemia or fluid overload may not be apparent in the initial stages of the process. As fluid accumulation in the body continues, certain signs and symptoms may become evident. These signs and symptoms can be interpreted properly by a trained medical professional. The following are some of the common signs and symptoms that may arise due to hypervolemia or fluid overload:
Hypervolemia in any region of the body may lead to swelling of that region. Swelling due to fluid accumulation is more prominent in the lower limbs due to the relatively poorer circulation of blood from the legs to the heart. In fact, swollen legs are one of the first signs of fluid accumulation or hypervolemia in the body.
Swelling may also occur in the arms, although this is usually to a lesser extent than the swelling in the legs. Swelling of the upper and lower limbs is technically referred to as peripheral edema. As the hypervolemia progresses, swelling may occur in more central parts of the body.
Read more on leg swelling.
Abdominal bloating refers to a swelling of the abdominal region due to accumulation of fluid. Technically, accumulation of fluid in the abdomen is referred to as ascites. In the initial stages of ascites, abdominal swelling may not be perceptible.
However, auscultation may provide evidence of fluid accumulation in these early stages. A visible swelling or distension of the abdomen occurs only when the fluid accumulation is significant. Eventually, abdominal bloating may also cause eversion of the belly button (technically referred to as the umbilicus).
Read more on ascites.
Sudden weight gain
Hypervolemia can cause sudden and significant weight gain. This is because a large part of the human body is composed of water. Any increase in the water content of the body can lead to weight gain that is perceptible within a short period of time (from days to hours. This is in contrast to the gradual weight gain that occurs in obesity.
Difficulty in breathing
Hypervolemia may also lead to difficulty in breathing. This usually occurs when fluid accumulates in the lungs. Breathing becomes more difficult when lying down. Persistent coughing may also occur in this condition.
Decreased urine output
Urine output may not be able to keep up with the amount of fluid that enters the body through oral consumption or intravenous administration. In some cases, the urine output may either cease completely or become abnormally low for a certain period of time.