Polyuria is a pathological condition characterized by an increase in urine output of more than 3 liters per day. It must be distinguished from pollakiuria (frequent urination with a normal daily volume of urine). Polyuria occurs with pathologies of the endocrine system, kidney disease or mental disorders. Polyuria is almost always naturally accompanied by polydipsia, i.e. increased fluid intake due to intense thirst. The condition is diagnosed by quantitative measurement of excreted urine per day. Correction consists in treating the underlying disease.
Several cases of physiological polyuria are possible. The most common non-pathological cause of polyuria, which can occur in any healthy person, is the ingestion of excess amounts of table salt (sodium chloride). An increase in the concentration of sodium ions in the blood leads to an increase in plasma osmolarity and excitation of the thirst centers of the brain. As a result, there is increased thirst and the following increase in the volume of diuresis.
As a rule, this form of polyuria is short-term. It is also possible to increase urine output as part of gestational diabetes insipidus, which develops at the end of the second trimester of pregnancy due to changes in the metabolism of antidiuretic hormone. 2-3 weeks after delivery, polyuria resolves on its own. Minor transient polyuria occurs after alcohol intake. In all other cases, polyuria is pathological.
The most common cause of polyuria is decompensated diabetes mellitus. Glucose has a high osmotic activity. With hyperglycemia, a large amount of glucose does not have time to be reabsorbed in the kidneys. As a result, along the osmotic gradient, water passively passes into the lumen of the renal tubules, which leads to an increase in the volume of urine excreted.
Polyuria in poorly controlled diabetes mellitus can reach 8-1 liters, its severity directly correlates with the level of glycemia. With a decrease in blood glucose to reference values, normalization of diuresis quickly occurs.
The second most common etiological factor for polyuria is medication. This is especially true of diuretics - loop and osmotic diuretics (furosemide, mannitol), which patients can take both for medical reasons and uncontrolled, for example, in order to reduce body weight.
In patients treated in a hospital, the cause of polyuria may be excessive parenteral administration of infusion solutions (saline, glucose, albumin). The severity of polyuria is determined by the dosage of the drug, but rarely reaches high numbers, usually it is no more than 4-5 liters.
Other drugs that can cause polyuria include:
Polyuria
The main regulator of water balance in the human body is antidiuretic hormone (vasopressin). By acting on special receptors in the kidneys, vasopressin stimulates the absorption of water, thereby reducing the amount of urine excreted. Deficiency of this hormone is observed in diabetes insipidus (NSD). There are 2 types of this disease - central, in which insufficient production of ADH develops, and nephrogenic, characterized by loss of sensitivity of the renal tubules to vasopressin.
Depending on the degree of ADH deficiency, the severity of polyuria can be different - from minor (up to 3-4 liters) to severe (more than 12 liters). In the central form of NSD, replacement therapy quickly leads to the disappearance of polyuria. Nephrogenic NDM is much more difficult to treat because the renal tubular receptors are insensitive to ADH. Causes of central NSD:
Causes of nephrogenic NSD:
An increase in daily diuresis is often observed during the resolution of acute renal failure, when the excretory function of the kidneys returns to normal. The severity and duration of polyuria depends on the degree of previous hyperhydration. On average, it lasts about 3-5 days, then goes away on its own. The persistence of polyuria for more than 1 day after acute renal failure indicates the development of tubular dysfunction.
This pathology is a mental disorder in which there is a compulsive uncontrolled consumption of water. Compared to all the other etiological factors listed above, in this case, polyuria is secondary to polydipsia. Often this condition can only be diagnosed after other causes of polyuria have been ruled out. After psychotherapy sessions, it is possible to achieve the cessation of compulsive behavior, and, accordingly, the normalization of diuresis.
An increased daily volume of diuresis requires an immediate visit to a general practitioner to determine the cause. The doctor asks the patient in detail about the presence of other complaints, about what chronic diseases he suffers from, what medications he takes, whether he is registered with an endocrinologist or nephrologist. Help in the differential diagnosis of polyuria is often provided by anamnestic data.
For example, a head injury or previous brain surgery may indicate diabetes insipidus, while weight loss, general and muscle weakness, and increased susceptibility to infectious diseases are characteristic of diabetes mellitus. Additional research methods are assigned:
In ambiguous clinical situations with difficulties in differentiating diabetes insipidus, special tests are carried out. In contrast to patients with NDM, a dry eating test (a ban on fluid intake for several hours) in patients with psychogenic polydipsia leads to a rapid normalization of osmolarity and relative density of urine and the disappearance of polyuria. The test with desmopressin makes it possible to clearly differentiate the central and nephrogenic forms of NSD. After taking desmopressin in central NDM, urine osmolarity increases, while in nephrogenic it remains low.
Urinalysis
There are no independent methods for correcting pathological polyuria. To normalize the volume of daily diuresis, it is necessary to treat the pathology against which it developed. If the cause of polyuria is a drug that the patient is forced to take for any disease, then the possibility of reducing the dosage or replacing it with an alternative drug should be considered.
Short-term polyuria during the recovery period after renal failure in the vast majority does not require any intervention and stops on its own. In the case of psychogenic polydipsia, the patient is referred to a psychotherapist. In diabetes, one of the main conditions for successful therapy is the observance of a low-carbohydrate diet. First of all, easily digestible carbohydrates are limited - chocolate, pastries, cakes. Preference is given to whole grain products (buckwheat, oatmeal).
For conservative treatment, the following drugs are used:
In severe clinical situations, for example, with prolonged decompensation of diabetes, the presence of morbid obesity, it is not possible to achieve normalization of blood glucose levels by conservative methods. Such patients are indicated for bariatric surgical interventions - this is gastric bypass, gastric banding. If NSD is caused by a craniopharyngioma, it is surgically removed by radical surgery or by aspiration and drainage of cystic cavities.
Polyuria necessarily requires a visit to the doctor, as it may indicate the presence of a serious illness. Ignoring this symptom often leads to adverse consequences. The occurrence of polyuria in patients with already diagnosed pathology (diabetes or diabetes insipidus) dictates the need for an urgent change in therapy tactics.