Polyuria

Introduction Polyuria, medical terminology, normal adult 24h urine output is about 1 ~ 2L, an average of 1.5L. Polyuria means that the body urinates more than 2,500 ml 24 hours a day. Polyuria is common in chronic glomerulonephritis. Under normal circumstances, the glomerular filtrate can reach 170L in 24h, and more than 99% of the water is reabsorbed by the renal tubule. If the glomerular function is normal or relatively normal and the renal tubular function is impaired, the reabsorption function will decrease. At most urine. If the glomerular hyperfunction is increased, although the tubular function is normal, exceeding the tubular workload is another cause of polyuria. The third cause is endocrine hormone deficiency, the most common is the lack of vasopressin or the inability of the tubular to fight diuretic hormone.

Cause

First, the cause classification

1. Endocrine and metabolic diseases

(1) Diabetes insipidus: due to hypothalamic-neuronal hypofunction, the secretion of antidiuretic hormone is reduced, causing a decrease in renal tubular reabsorption and causing polyuria.

(2) Diabetes: Due to excessive blood sugar, there is a large amount of sugar in the urine, which can cause solute diuresis. As the blood sugar rises, the body increases the amount of drinking water for metabolism, so that dilution of blood is also the cause of polyuria.

(3) Potassium deficiency: In the case of primary aldosteronism, due to hypothalamic-neuronal hypofunction, the secretion of antidiuretic hormone is too small, and the patient is thirsty and drink more (more than 4 liters per day). Polyuria loses water, and as the amount of urine increases, the loss of potassium in the urine increases and causes refractory hypokalemia. Long-term hypokalemia secondary to various reasons, can cause renal tubular vacuolar degeneration and even tubular necrosis, said potassium loss nephritis, renal tubular reabsorption of potassium disorders, a large amount of potassium lost from the urine, patients with polydipsia and polyuria Laboratory tests for the impairment of renal tubular function in addition to hypokalemia are characteristic.

(4) Hypercalcemia: In hyperparathyroidism or multiple myeloma, elevated blood calcium impairs the renal tubules, causing a decrease in reabsorption function and polyuria. It is also easy to form urinary calculi, which further damages the function of the renal tubules and aggravates the condition.

2. Polyuria caused by kidney disease

Found in the early stages of chronic renal failure, this time is characterized by an increase in nocturia. Acute renal failure in acute renal failure or non-oliguric type of acute renal failure can manifest polyuria, which is a manifestation of tubular dysfunction. Types of renal tubular acidosis generally have polyuria. Type I renal tubular acidosis, also known as distal renal tubular acidosis, is due to dysfunction of distal renal tubules, which is characterized by persistent metabolic acidosis, alkaline urine, and urine pH generally above 6. Hyperchloremia, hypokalemia, low blood steel, hypocalcemia. Type II renal tubular acidosis is a metabolic acidosis caused by the absorption of titanium bicarbonate by the proximal tubules. Since the proximal tubules cannot completely absorb the sugar, the increase in urine glucose excretion is characterized by renal glucosuria. Type III renal tubular acidosis is a simultaneous damage of the proximal distal tubule, and its clinical features are characterized by both type I and type II. Type IV renal tubular acidosis is caused by lack of aldosterone or distal renal tubules, which is insensitive to aldosterone, low in response to polyuria, metabolic acidosis, and hyperkalemia. The commonality of various types of renal tubular acidosis is: polydipsia and polyuria, metabolic acidosis, alkaline urine, urine pH of 6 or more, type II type III can appear renal glycosuria type IV hyperkalemia.

3. Solute polyuria

For treatment reasons, mannitol, sorbitol, and hyperglycemia may be used to express polyuria. If diuretic drugs are used at the same time, polyuria is more significant.

4. Other

Drink plenty of water, drink tea, eat too salty or excessive sugar can also be more urine.

an examination

Related inspection

Urine regular urine sugar

Urine routine, urine sugar, blood sugar, blood electrolyte determination, blood antidiuretic hormone determination.

Test result judgment

(1) Urine routine examination: The urine specific gravity is lowered, suggesting that it may be polyuria caused by diabetes insipidus.

(2) Determination of urine sugar and blood sugar: urine sugar is positive, blood sugar is elevated, suggesting that the urine is caused by diabetes.

(3) Determination of blood electrolytes: increased blood calcium, suggesting that polyuria may be caused by hyperparathyroidism. Lower blood potassium suggests a polyuria caused by hypokalemia.

(4) Determination of blood antidiuretic hormone: lower, suggesting diabetes insipidus polyuria.

Differential diagnosis

Diabetes insipidus

Diabetes insipidus is a disease caused by hypothalamic-hyperthoracic function and excessive secretion of antidiuretic hormone. The main clinical manifestations are thirst, polydipsia, polyuria, and water loss.

2. Diabetes

A typical medical history should be polydipsia, polyphagia, polyuria, and weight loss. Atypical medical records are more common in the elderly, especially those who are older and obese. They show more drinking and more urine, but they do not show more food. Diabetes laboratory tests showed high blood sugar, high urine sugar, abnormal insulin release and C-peptide examination. Atypical cases must be tested for glucose tolerance or taro test.

3. Renal polyuria

Attention to the history of kidney disease, examination of renal function, especially the examination of renal tubular function is abnormal.

4. Primary aldosteronism

Patients with refractory hypertension, refractory hypokalemia, periodic muscle spasms, paralysis, convulsions and spasms. Adrenal adenoma or hyperplasia can be found by CT or MRI.

5. Primary hyperparathyroidism

It is due to parathyroid adenoma (90%) hypertrophy (10%) and cancer (rarely seen), patients with polydipsia and polyuria, weak muscle weakness, nausea and vomiting, constipation. Laboratory tests for high blood calcium, high urinary calcium, and elevated alkaline phosphatase. X-ray examination, bone decalcification, bone absorption.

6. Spiritual polydipsia, polyuria

Patients can often be thirsty, when the amount of urine can be significantly reduced, and the relative density of urine can be increased to above 1.015. Patients are also susceptible to a range of clinical manifestations of neurosis. The water deprivation test or the hypertonic saline test can be differentiated from diabetes insipidus.

7. Hereditary renal diabetes insipidus

Rare disease, belonging to hereditary diseases, autosomal abnormalities, female heredity, male onset, family history, but can occur in generations. After birth, it shows polyuria, and polyuria precedes polydipsia. The water-free test and the hypertonic saline test did not respond.

8. Hypokalemia

Generally, low potassium does not show polyuria, only long-term low potassium, such as more than 3 months, stubborn hypokalemia, causing renal tubular vacuolar degeneration, said potassium-induced nephritis when the performance of polyuria, low potassium, urinary potassium High, impaired renal tubular function is its clinical features.

9. Acute renal failure

Acute renal failure is clinically divided into the early stage of renal failure, oliguria and anuria, polyuria, recovery period, and urine volume increase during the polyuria period. It is generally divided into three forms: jumping, daily urine output. Increase in more than 100%, the prognosis of this type is good; stepwise increase, daily urine volume increased by 50%-100%, the prognosis of this type is also good; slow increase, daily increase of urine volume below 50%, representing kidney Incomplete management of tubule function or new factors affect the recovery of renal function, common infections, nephrotoxic drugs or electrolyte disorders should be resolved in a timely manner. This type of oliguria and auria is generally longer, often more than half a month, some patients can Direct transition to chronic kidney failure, causing permanent kidney damage. In about l/3 cases, acute renal failure manifests polyuria from the onset of the disease, called polyuria type acute renal failure.

10. Chronic renal failure

In the early stage of chronic renal failure, it often shows polyuria, and the main amount of nocturia increases, which means renal tubular dysfunction. At this time, the relative density of urine is low, often fixed at l010-l.012, low urine osmotic pressure, radionuclide kidney The graph shows a low level curve.

11. Obstructive nephropathy

It is a group of diseases mainly involving the renal interstitial-tubules, so it is also called tubule-interstitial nephropathy. Its etiology is complex, common in infection caused by pathogenic microorganisms; immune function damage; nephrotoxic substance damage; renal blood supply disorders metabolic diseases such as hyperuricemia, hypercalcemia; physical factors found in long-term exposure X-ray or tumor radiation therapy Reflux nephropathy caused by urinary tract obstruction and hereditary disease polycystic kidney disease. The causes are different, and the clinical manifestations are different, but the common feature is renal interstitial and renal tubular damage. Because of tubular damage, the dysfunction of the small tube is polyuria.

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