Diuresis is the excretion of urine by the kidneys. Diuresis can be forced therapeutically and used for detoxification. In diseases such as diabetes mellitus, diuresis exceeds the average normal value of 1.5 liters per day.
What is diuresis?
Diuresis is the excretion of urine by the kidneys. The kidneys are paired bean-shaped organs whose main function is detoxification and urine formation. Urine formation consists of steps of filtration, reabsorption and concentration. Especially with secretion and reabsorption, the kidneys have a significant participation in systemic regulations. The organs regulate human water and electrolyte balance. They also ensure the acid-base balance of the acid-base balance. The medical term for the volume of urine is the amount of urine that can be provided by the kidneys and subsequently excreted (micturition) in a defined time interval of 24 hours. In the normal state of the kidneys, the principle of antidiuresis applies. Under these conditions, the urine time volume averages between 1.5 and two liters per day. With diuresis, the urine time volume can increase many times over. Diuresis, in the expanded definition, refers to urine excretion by the kidneys. In isolated sources, the term diuresis refers to urine excretion levels above the average normal value of two liters. Basically, diuresis can take place therapeutically, have pathological backgrounds, or be brought about by certain diets.
Function and task
Diuresis, in the sense of urine excretion, is the main function of the kidneys. Diuresis contributes significantly to the detoxification of the human body and regulates water as well as electrolyte balance. The first step of urine formation corresponds to the filtration of primary urine within the renal corpuscles. Primary urine averages 180 liters per day. Blood plasma is forced through the inner leaf of the so-called Bowman’s capsule during primary urine formation. Larger blood components do not penetrate because the blood vessel traps them. Counterpressure enters from the capsular space of the Bowman capsule. In addition, protein molecules in the blood create back pressure by retaining water in the blood vessel. Due to the pressure-counterpressure principle, the effective filtration pressure in the Bowman capsule is about eight mmHg. After the primary urine is formed by the pressure-counterpressure principle, the kidneys modify the primary urine. This step takes place in the proximal tubule and involves the reabsorption of components such as electrolytes, water, glucose and residual protein into the blood. The volume of primary urine is reduced by these processes to an average of 19 liters per day. In the final step of urine formation, the kidneys concentrate the urine in the so-called loop of Henle and in the collection tubes using the countercurrent principle. Essentially, water is removed from the primary urine during concentration without any additional energy expenditure. The concentration process in the loop of Henle produces the secondary urine. Under normal circumstances, this secondary urine averages about 1.5 liters per day. All the processes listed empower the kidneys for diuresis. Hormones such as adiuretin (ADH) oppose diuresis by promoting water reabsorption. Aldosterone increases sodium reabsorption at the same time. Physical variables acting on the body also influence diuresis. For example, diuresis activity increases with cold stress or pressure stress. Low air pressure at altitudes of around 3000 meters also increases diuresis. The so-called cold diuresis is related to a decreased production of the hormone ADH. Thus, a person’s environment has an influence on his or her diuresis activity. Diet can also influence diuresis. For example, caffeine contained in coffee exhibits diuretic effects. However, when coffee consumption is habitually high, the kidneys do not increase their diuresis.
Diseases and ailments
Different measures of medicine influence diuresis externally. Diuretics are the best-known procedure for increasing diuresis. These drugs are also called diuretics and are indicated in different contexts. In various renal and cardiovascular diseases, forcing urination via diuretics can reduce circulatory stress. For this reason, diuretics are often used in heart failure.Patients with poisoning also receive a form of forced diuresis. This type of diuresis takes the form of intensive medical detoxification measures. Toxic and water-soluble substances are driven out of the body by increased urine production. In various sources, the term diuresis is used in the context of pathologically high urinary output from the kidneys. A pathological form of diuresis may be osmotic diuresis. This is an increased excretion of water by the kidney caused by osmotically active substances. Concentration of urine in a healthy body occurs predominantly in a passive manner. In this process, fluid is removed from the tubular fluid by osmosis. The more osmotically active particles the fluid contains, the less of it can be reabsorbed. The increasing number of osmotically active elements decreases the osmotic gradient between tubular fluid and surrounding tissue. As a result, water reabsorption is reduced and the urine volume increases. From clinical practice, physicians are familiar with osmotic diuresis, especially in connection with diseases such as diabetes mellitus. This metabolic disease is often manifested by symptoms such as polyuria. In polyuria, the normal physiological amount of urine for the age group increases daily to more than 1500 milliliters per square meter of body surface. This phenomenon is related to the glucose excess in diabetes mellitus. In the face of the oversupply, the proximal tube has too low a transport capacity for glucose. For this reason, osmotically active glucose particles remain in the tubule. The reabsorption of water is thus prevented. The patient’s diurnal diuresis thus increases above normal.
