Polydipsia

Introduction Diabetes insipidus is often accompanied by polydipsia and polydipsia, or fever, dehydration, or even convulsions. Diabetes insipidus is caused by the lack of antidiuretic hormone (ie, arginine vasopressin, AVP for short) and the dysfunction of renal tubular reabsorption of water, which causes polyuria, polydipsia, polydipsia and low specific gravity urine. a disease. The disease is caused by lesions in the hypothalamic-neuronal pituitary, but some cases have no obvious cause. Diabetes insipidus can occur at any age, but it is more common in young people.

Cause

Idiopathic: There is no obvious cause in the clinic. A few families with idiopathic diabetes insipidus have a family history and are autosomal dominant.

Secondary: Mostly caused by lesions in the hypothalamic-neuronal pituitary.

Reason one: lack of water in the human body leads to thirst. When the weather is hot, heavy physical labor, blood loss, burns, vomiting, diarrhea, and a lot of sweating due to high temperature (heat stroke), people will feel thirsty because of the thirst caused by severe water shortage in the human body.

Reason 2: One of the effects of thirst hormones caused by diabetes is to coordinate the metabolism of water and salt in the human body. Once the balance of this hormone is destroyed, it can cause frequent thirst.

Cause three: thirst caused by brain damage Some people will also be thirsty after brain injury or neurosurgery. Patients are often fatal and dangerous in one day or even an hour.

an examination

Related inspection

Glycemic glycosylated hemoglobin

The diagnosis of diabetes insipidus is generally not difficult. Anyone who has polyuria, polydipsia, polydipsia, and low specific gravity should consider the possibility of diabetes insipidus. However, the diagnosis must be based on the following diagnostic tests.

1. Water-free experiment: After a certain period of time, normal people are forbidden to drink water, the body's water is reduced, plasma osmotic pressure is increased, AVP is secreted a lot, so urine volume is reduced, urine is concentrated, urine specific gravity and osmotic pressure are increased. Due to the lack of AVP in patients with diabetes insipidus, the urine volume after water ban is still high, and the urine specific gravity and osmotic pressure are still low.

Method: This test should be carried out under close observation. Body weight, blood pressure, urine volume and urine specific gravity or osmotic pressure were measured before water ban. The water-free time is 8-12h, urinating every 2h during the water-free period, measuring urine volume, urine specific gravity or osmotic pressure, measuring body weight and blood pressure every hour, such as more urination, weight loss of 3%-5% or significant decrease in blood pressure The test should be stopped immediately and the patient should be allowed to drink water.

Results: The urine volume of normal people was significantly reduced after the water was banned. The urine specific gravity exceeded 1.020, and the urine osmotic pressure exceeded 800mOsm/kg.HO. No obvious water loss occurred. In patients with diabetes insipidus, the urine volume is still high after the water is banned. The urine specific gravity generally does not exceed 1.010, and the urine osmotic pressure does not exceed the plasma osmotic pressure. Some patients still have a certain amount of AVP secretion, but not enough to maintain normal regulation. After ban, the urine specific gravity can exceed 1.015, but less than 1.020, the osmotic pressure can exceed the plasma osmotic pressure, but it is still insufficient compared with normal, which is partial. Diabetes insipidus. This method is simple and feasible, and it is helpful for the diagnosis of diabetes insipidus. However, the maximum concentration of urine after water in addition to AVP depends on the state of hyperosmolarity of the renal pulp. Therefore, the maximum urine specific gravity or osmotic pressure can be achieved only after the water is banned. To diagnose diabetes insipidus, sometimes it is not reliable.

2, no water - vasopressin test: water for a certain period of time, when the urine is concentrated to the maximum osmotic pressure and can not rise again, the injection of vasopressin. After normal people have been banned from water, a large amount of AVP has been released. After injection of exogenous AVP, urine osmotic pressure is no longer elevated, and AVP deficiency in patients with diabetes insipidus. After injection of exogenous AVP, urine osmotic pressure is further increased.

Method: The time of water inhibition depends on the degree of polyuria in the patient. The weight can be several hours, and the lighter time is more than ten hours or longer. When the urine osmotic pressure reaches the peak flat top, that is, the osmotic pressure of the water is no longer increased. Blood was drawn for plasma osmotic pressure, and vasopressin was injected subcutaneously at 5 U, and urine osmotic pressure was measured 1 h after injection. Compare urine osmotic pressure before and after injection.

RESULTS: After sputum injection, the osmolality of normal people did not generally increase. Only a few people increased slightly, but did not exceed 5%. In patients with diabetes insipidus, the osmolality of vasopressin after injection of water is further increased, which is at least 9% more than before injection. The more severe the AVP deficiency, the greater the percentage increase. This method is simple and reliable, but it must also be carried out under close observation to avoid severe dehydration during the water-free process.

3, hypertonic saline test: After normal intravenous infusion of hypertonic saline, plasma osmotic pressure increased, AVP released a lot, urine output decreased significantly, urine specific gravity increased. In patients with diabetes insipidus, the amount of urine does not decrease after the infiltration of hypertonic saline, and the urine specific gravity does not increase. However, after the injection of vasopressin, the urine volume is significantly reduced, and the urine specific gravity is significantly increased. This test has certain effects on patients with hypertension and heart disease. Dangerous, now used less.

4, plasma AVP determination (radioimmunoassay) normal human plasma AVP (random drinking water) is 2.3-7.4pmol / L, can be significantly increased after water ban. However, patients with this disease can not reach normal levels, and do not increase or increase after the water is not allowed.

After the diagnosis of diabetes insipidus is confirmed, the cause must be further clarified. Sella radiographs, visual field examinations, etc. should be performed; if necessary, CT or magnetic resonance examinations may be performed to exclude tumors in or near the pituitary.

Diabetes insipidus should be identified with the following diseases characterized by polyuria.

1. Mental polydipsia: Mainly manifested as polydipsia, polydipsia, polyuria and low specific gravity urine, very similar to diabetes insipidus, but AVP is not lacking, mainly due to mental factors causing polydipsia, polydipsia, resulting in more Urine and low specific gravity urine, these symptoms can fluctuate with emotions, accompanied by other symptoms of mental disorders, the above diagnostic tests are within the normal range.

2. Renal diabetes insipidus: It is a hereditary disease. Its abnormal gene is located in the Xq28 part of the X chromosome. The renal tubule is not sensitive to AVP. The clinical manifestations are very similar to those of diabetes insipidus. Mostly for boys, the amount of urine does not decrease after injection of vasopressin! The specific gravity of urine does not increase! The plasma AVP concentration is normal or elevated.

3, chronic kidney disease: a variety of diseases including chronic kidney disease, especially renal tubular disease, hypokalemia, hypercalcemia, etc. can affect the kidney concentration function and cause polyuria, thirst and other symptoms, but there are corresponding The clinical features of the disease, and the degree of polyuria is also relatively light.

Differential diagnosis

Symptoms of polydipsia and polydipsia

Thirsty and thirsty: The performance is subjective and thirsty. If you want to drink water, the symptoms will improve slightly after drinking, but soon you will be thirsty. 1. Have thirst and drink more, should be alert to the occurrence of diabetic ketosis, early symptoms of ketosis often have more urine, thirst, more drink, fatigue and so on. The ketone body, blood sugar and blood ketone body should be checked in time, except for ketoacidosis. If you suspect diabetes, you can measure fasting blood glucose, or do glucose tolerance test to confirm the diagnosis. 2. But thirst is not necessarily diabetes, maybe stomach fire, pay attention to heat.

Drinking more: People with diabetes can't convert the sugars that the body absorbs from food into liver glycogen and muscle glycogen at normal levels. The sugar they absorb cannot be broken down into glucose in the body's sugar cycle. It is reused, and the kidneys used to filter the impurities in the blood absorb the glucose in the blood into the urine, then transfer it to the bladder, and then discharge it. The osmotic pressure of the urine is high, and the water is discharged more. Of course, when the body needs less water, it is thirsty, so drink more.

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