The causes of polyuria are varied, as it is usually one of the symptoms of the disease. Excessive urination is most often associated with uncontrolled diabetes, but in some cases it may indicate other, equally serious diseases, such as, for example, hyperparathyroidism or cancer. Check what the polyuria shows.

Polyuria( polyuria ) is a disorder in which you pass more than 3 liters of urine per day, with the correct amount being 2 -2.5 liters.Excessive urinationmay be the result of low ambient temperature or high altitude (in this case, it is the result of the organism's adaptation to specific conditions). However, excessive urine output usually occurs in the course of uncontrolled diabetes. Other common causes of polyuria includepolydipsia , i.e. excessive fluid intake (as a result of increased thirst), diabetes insipidus, and renal diabetes insipidus.

Excessive urinationmust be distinguished frompollakiuria , which is defined as the need to urinate repeatedly during the day, but with normal or reduced urination. quantity. Another problem isnocturia(urinating at night).

Polyuria - how does it happen?

The tidal balance in the body is controlled by a complex process:

  • fluid intake
  • kidney perfusion (blood flow through the kidneys)
  • glomerular filtration (filtration is the first stage of urine formation. Water, vitamins, amino acids, sodium, potassium, calcium, magnesium, chlorine, glucose ions are then filtered)
  • reabsorption of water in the collecting tubules of the kidneys (i.e. reabsorption of most of the fluid filtered through the glomeruli. Sodium, potassium, magnesium, calcium and glucose ions are reabsorbed and then absorbed by the blood vessels)

Fluids ingested increase blood volume, which enhances renal perfusion and glomerular filtration, resulting in increased urine output. This process is inhibited by the atidiuretic hormone (ADH - vasopressin), secreted in the hypothalamic-pituitary system. Its role is to regulate water resources in the body and prevent excessive water supplyher loss in urine. ADH increases the reabsorption (reabsorption) of water from the glomerular filtration (primary urine) in the renal tubules, thanks to which the urine is concentrated to approx. 1.5 l / day of final urine. As a consequence, the amount of urine passed out is reduced. Pituitary gland dysfunction, namely secretion disorders or the lack of a proper response to the antidiuretic hormone ( although the amount secreted is normal), causes water not to be reabsorbed and to be excreted in excess with diluted urine. This is what happens with diabetes insipidus.

Polyuria - diabetes insipidus

Diabetes insipidus is associated with reduced or no secretion of vasopressin (central diabetes insipidus), or the insensitivity of the renal tubules to this hormone (nephrogenic diabetes insipidus).

In some patients, central diabetes insipidus is the result of genetic disorders and in such cases it may be inherited. Often the disease is a consequence of trauma, pituitary gland surgery, hypoxia, or ischemic stroke. The main symptom of the disease is sudden increased thirst and passing a large amount of urine (up to 4-15 liters per day), with a very low density (specific gravity). Additionally, there may be symptoms resulting from the cause of the disease (e.g. symptoms of a brain tumor).

Diabetes insipidus can also be congenital or appear in the course of many diseases, such as:

  • amyloidosis
  • sickle cell anemia
  • Sjogren's band
  • Fanconi's band
  • Lightwood-Albright team
  • reactive arthritis - formerly Reiter's syndrome
  • diseases in the course of which hypercalcemia occurs (cancer, hyperparathyroidism, granulomatous diseases)
  • hyperemia (polycythemia)
  • migraine
  • Conn's syndrome, or primary hyperaldosteronism
  • Glinski-Simmonds disease
  • heart failure (very often associated with ventricular tachycardia and atrial fibrillation)

The characteristic feature of diabetes insipidus ishypernatremia , i.e. an increase in blood sodium concentration above 142 mmol / l.

Polyuria - decompensated diabetes

The cause of polyuria may be a high concentration of filtrate in the renal tubules, which causes the so-called osmotic diuresis. This is the excretion of large amounts of urine due to the presence of an osmotic active substance in the urine (which has the ability to draw an increased volume of water into the cells), which causes impaired reabsorption of water in the renal tubules.

An example is osmotic diuresis in decompensated diseasediabetes. A high concentration of glucose in urine (>250 mg / dL) exceeds the resorptive capacity of the tubules, leading to high levels of glucose in the renal tubules and secondary passive transport of water to the urethra, which increases the volume of urine excreted. Decompensated diabetes manifests itself as thirst and polyuria, especially in children or obese adults with a family history of type 2 diabetes.

Polyuria - Kidney Disease

Another example of osmotic diuresis is polyuria in chronic kidney disease. Then the osmotically active substance is urea, the concentration of which in the blood is increased. Diuresis with this mechanism is also induced for therapeutic purposes, during:

  • intravenous mannitol
  • infusion of isotonic or hypertonic saline
  • high-protein tube feeding
  • removal of the obstruction in the outflow of urine - polyuria occurring after insertion of a Foley catheter in patients with an obstruction in the outflow of urine from the bladder

Polyuria - polydipsia

Polydipsia involves excessive fluid consumption (as a result of increased thirst). Polydipsia can be:

  • primary (changes in the hypothalamus within the "thirst center") - applies to people with lesions within the hypothalamus (eg in sarcoidosis). It also often occurs in decompensated diabetes (hyperglycemia), hyperthyroidism, water and electrolyte disturbances (dehydration, sweating) and hypercalcemia (over 13 mg / dl);
  • psychogenic - most often affects middle-aged women with symptoms of anxiety, history of mental illness;

Polydipsia is characterized byhyponatremia , i.e. low sodium in the blood (its concentration drops below 137 mmo / l).

Polyuria medication

The cause of polyuria may be medications such as lithium (taken for bipolar disorder), cidofovir, foscarnet, which cause nephrogenic diabetes insipidus.

Other agents that can contribute to polyuria are diuretics, used for symptoms of fluid overload (heart failure, peripheral edema). There may also be cases when these drugs are used arbitrarily to lose weight. It is worth knowing that diuretics also include coffee, tea and other drinks containing caffeine, as well as alcohol.

References:The Merck manual. Clinical Symptoms: A Practical Guide to Diagnostics and Therapy , pp. ed. Porter R., Kaplan J., Homeier B., Wrocław 2010

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