Health
Fact-checked

At WiseGEEK, we're committed to delivering accurate, trustworthy information. Our expert-authored content is rigorously fact-checked and sourced from credible authorities. Discover how we uphold the highest standards in providing you with reliable knowledge.

Learn more...

What is Osmotic Diuresis?

Geisha A. Legazpi
Geisha A. Legazpi

Osmotic diuresis, or solute diuresis, refers to increased urination accompanied by daily solute excretion of more than 750 milliosmols. An increase in the filtration of solutes that could not be reabsorbed by the kidneys, such as urea or glucose, can lead to impaired reabsorption of sodium and water. This leads to osmotic diuresis. Osmotic diuresis leads to water loss from the renal system, thus it can cause hypovolemia or an abnormally low blood volume. It can occur in patients who use pharmacological diuretics or in patients who have poorly controlled diabetes mellitus.

Diuresis refers to the increase in urine volume output or urination. It is an important concept in nephrology, particularly because it can be used to reduce blood volume in hypervolemic states such as hypertension and edema. In osmotic diuresis, substances that are not easily reabsorbed by the renal tubules are retained in the lumen, causing an increase in osmotic pressure. With the phenomenon of osmosis, wherein water goes through a semipermeable membrane into a solution of high solute concentration, water then goes to the lumen. This leads to a reduction in water reabsorption, thereby resulting in increased urine output.

Diuresis refers to the increase in urine volume output or urination.
Diuresis refers to the increase in urine volume output or urination.

Osmotic diuretics are substances that are not easily reabsorbed by the renal tubules. These substances include urea, sucrose, and mannitol. Mannitol mainly acts on the proximal tubules and inhibits both water and solute reabsorption in the kidney tubules by increasing the osmolarity of the renal tubular fluid. It is used in medical conditions wherein there is an increase in the amount of body fluids such as hypertension, cerebral edema, kidney failure, and glaucoma. Sometimes, it is used to treat a drug overdose with aspirin, bromides, and barbiturates.

High blood pressure can cause an increase in the body's fluid levels.
High blood pressure can cause an increase in the body's fluid levels.

Disease states associated with failure of the kidneys to reabsorb excess solutes from the tubular fluid may also result in osmotic diuresis. In diabetes mellitus, for example, the blood glucose concentration levels become abnormally elevated. When the concentration of glucose in the blood reaches about 250 milligrams per deciliter, only a very small amount of glucose is reabsorbed by the tubules. At this point, the “transport maximum” of the tubules is exceeded.

Diuretic medications are sometimes used to treat hypertension.
Diuretic medications are sometimes used to treat hypertension.

The increased load of glucose in the kidneys exceeds the capacity of the tubules to reabsorb glucose. Excess glucose in the tubules serves as an osmotic diuretic, leading to rapid loss of fluid and frequent urination or polyuria. The polyuria of diabetes is accompanied by polydipsia, or increased frequency of drinking. Polydipsia occurs due to the detection of high urine output and activation of the thirst mechanism.

Discussion Comments

Phaedrus

Increased urination and excessive thirst were two of the symptoms I had when I was diagnosed with type 2 diabetes, so this must be the more scientific explanation. It's the excess sugar in the blood that makes things harder for the kidneys to process.

Post your comments
Login:
Forgot password?
Register:
    • Diuresis refers to the increase in urine volume output or urination.
      By: Chatchai
      Diuresis refers to the increase in urine volume output or urination.
    • High blood pressure can cause an increase in the body's fluid levels.
      By: dambuster
      High blood pressure can cause an increase in the body's fluid levels.
    • Diuretic medications are sometimes used to treat hypertension.
      By: Monkey Business
      Diuretic medications are sometimes used to treat hypertension.
    • In osmotic diuresis, substances that are not easily reabsorbed by the renal tubules are retained in the lumen, causing an increase in osmotic pressure.
      By: 7activestudio
      In osmotic diuresis, substances that are not easily reabsorbed by the renal tubules are retained in the lumen, causing an increase in osmotic pressure.
    • The polyuria of diabetes is accompanied by polydipsia, or increased frequency of drinking.
      By: Aurelio
      The polyuria of diabetes is accompanied by polydipsia, or increased frequency of drinking.
    • Osmotic diuresis can strike patients whose diabetes is inadequately managed.
      By: dalaprod
      Osmotic diuresis can strike patients whose diabetes is inadequately managed.
    • Osmotic diuretics like mannitol may be used to treat a drug overdose with aspirin, bromides, and barbiturates.
      By: 18percentgrey
      Osmotic diuretics like mannitol may be used to treat a drug overdose with aspirin, bromides, and barbiturates.