Renal diabetes

Introduction to renal diabetes Renalglucosuria refers to a condition of diabetes caused by a decrease in glucose function in the proximal tubules when the blood glucose concentration is normal or lower than the normal renal sugar threshold. Clinically divided into primary renal glucosuria and secondary renal glucosuria. In addition to family history, primary renal glucosuria usually lacks symptoms such as polydipsia, polyuria, and pyuria, which are common in diabetic patients. Most of them are found by routine urine analysis. Primary onset, generally asymptomatic, does not affect development, and has a good prognosis. basic knowledge The proportion of illness: 0.09% Susceptible people: no special people Mode of infection: non-infectious Complications: dehydration, malnutrition, low blood sugar

Renal diabetes

(1) Causes of the disease

The causes of renal diabetes are divided into primary and secondary.

1. Primary renal glucosuria: also known as familial renal glycosuria (familial renal glycosuria), mostly autosomal recessive genetic disease, and some are dominant inheritance, the disease can be divided into two types according to the sugar titration curve:

(1) Type A: renal sugar threshold and renal tubular glucose maximum reabsorption rate (TMG) are reduced. When blood glucose is not high, renal tubules are also less than normal for glucose reabsorption, so it is true diabetes, which can be a separate tubular Glucose transport is impaired, but often combined with other renal tubular transfusion defects, such as Fanconi syndrome, Lowe syndrome.

(2) Type B: The renal sugar threshold is lowered and TMG is still normal, so it is pseudo-renal glucosuria. It is because the reabsorption function of glucose by individual nephron is reduced, and the maximum absorption rate of glucose is not reached. The renal sugar threshold is reduced and clinically common.

2. Secondary renal glucosuria: less common, can be secondary to chronic kidney diseases such as chronic interstitial nephritis, nephrotic syndrome, multiple myeloma or other nephrotoxic substances such as lead, cadmium, mercury, oxalic acid, cyanide Compound and other hereditary diseases Fanconi syndrome, Lowe syndrome, cystine accumulation disease and so on.

(two) pathogenesis

Normal renal tubules have a strong reabsorption potential for glucose. Under physiological conditions, there is only a very small amount of glucose excretion in the urine (<1.0g/24h). The routine routine examination of urine glucose is negative (more than 2.22mmol/L), and the renal threshold is 7.8 ~ 10.6mmol / L (140 ~ 190mg / dl), the generally tested reagent strips require urinary glucose content > 2.2mmol / L (40mg / dl), normal urine secretion of trace amounts of glucose, its concentration <0.83mmol / L (15mg/dl), the test result was negative, and the average value measured by the above method was 4.15mmol/24h (75mg/24h), and its range was 0.83-7.5mmol/24h (15-135mg/24h) or 300nmol/min (60 ~ 540nmol / 24h), only higher than the normal range of 7.3 ~ 17mmol / (24h · 1.73m2) [132 ~ 316mg / (24h · 1.73m2)] can appear urine sugar positive.

In the absence of interference factors, the ability of the kidney to reabsorb sugar depends on the number of renal reperfusion cells and the ability of the renal tubular epithelial cells, and the two major parameters of renal tubular glycemic maximum reabsorption rate (MTG) and renal sugar threshold. One indicator measures the reabsorption of glucose by the kidneys.

MTG actually refers to the total amount of glomerular filtration glucose (the product of glomerular filtration rate and blood glucose concentration) and the amount of urine glucose excretion per unit time when the blood glucose concentration is much higher than the renal sugar threshold. (The product of urine sugar concentration and urine volume), from another perspective, MTG is the product of the maximum reabsorption rate of a single tubular glycoside and the total number of nephrons, so MTG is clearly affected by the total number of nephrons and individual renal tubular function. In addition, the reabsorption rate of sodium ions can be used as an interference factor for MTG. The normal human MTG is 250-375 mg/min. Men are higher than women, and children are the same as adults after correction for body surface area, but the elderly are lower.

Renal sugar threshold refers to the initial blood glucose concentration that can cause diabetes after the blood sugar gradually rises. The size of the renal sugar threshold is not only related to the ball-tube balance function of a single nephron, but also to the sugar reabsorption threshold of each kidney unit of the whole kidney. Consistently, the overall renal sugar threshold actually reflects the renal sugar threshold of the part of the nephron that has the worst re-absorption of sugar function. The normal human sugar threshold is 8.88 mmol/L (160-190 mg/dl), according to GFR. At 125ml/min, the sugar load in the filtrate at this time is: (160 ~ 190mg / dl) × 125ml / min = 200 ~ 237mg / min, this value is obviously smaller than MTG, the phenomenon of the emergence and sugar and reabsorbent carrier Affinity is related to the heterogeneity of renal unit reabsorption capacity.

In short, the pathogenesis of this disease is unclear and may be related to the following factors:

1. The ratio of the proximal tubule surface area to the glomerular filtration membrane area is reduced, resulting in a tube imbalance.

2. The function of the transport system of renal tubular to glucose reabsorption is not balanced.

3. The accumulation of different concentrations of glucose by renal tubular cells reduces the number of glucose reabsorbers, or changes in affinity or gradient disorder.

4. The permeability of the tubular cell membrane to glucose is reduced, and in addition, the absorption of glucose by the intestinal tract is also impeded.

Renal glucosuria prevention

The disease is a hereditary disease, there is no effective preventive measures at present, such as the small intestinal glucose-galactose malabsorption syndrome, the feeding of fructose can effectively prevent this disease, secondary renal glucosuria mainly active treatment of primary disease, prevent kidney Toxic damage to protect the normal function of the glomerulus.

Renal glucosuria complications Complications dehydration malnutrition hypoglycemia

Can be dehydrated, malnutrition, hypoglycemia and so on.

Renal glucosuria symptoms common symptoms polyuria polydipsia diarrhea renal tubular reabsorption disorder pyuria dehydration

1. Primary renal glucosuria: is a genetic factor caused by proximal renal tubules to glucose reabsorption, clinically there are two diseases: intestinal glucose-galactose malabsorption syndrome and benign familial Renal diabetes.

Intestinal glucose-galactose malabsorption syndrome is a congenital defect of galactose and glucose transport in jejunum and renal tubular epithelial cells, mainly manifested as intestinal malabsorption, watery diarrhea in primary children, dehydration and malnutrition, and detectable stool A large amount of galactose, can be cured by feeding fructose, kidney disease is lighter, and only seen in homozygous zygotes.

Benign familial renal glucosuria is an autosomal dominant hereditary disease and can be divided into two types: type A is a decrease in renal sugar threshold and MTG, and may have Fanconi syndrome; type B only has kidney sugar. The threshold is lowered, and the degree of diabetes varies from person to person. In the most severe cases, the renal tubules hardly absorb glucose.

In addition to family history, patients with primary renal glucose and glucose usually lack the symptoms of polydipsia, polyuria, pyuria, etc., which are common in diabetic patients. Most of them are found by routine urine analysis. The primary disease is generally asymptomatic and does not affect development. Prognosis is good, may be due to compensatory appetite hyperthyroidism, supplemented with loss of urine sugar, a small number of children also have hypoglycemia symptoms due to excessive urine sugar, but generally do not change to metabolic diabetes, a few cases can have more drink, more Urinary, polyphagia and other symptoms, often continue to have diabetes, urine sugar is generally <30g/24h, while fasting blood glucose is normal, glucose tolerance test is normal, severe urinary glucose loss can occur ketosis, urinary ketone positive, easily misdiagnosed as Diabetes, but it should be pointed out that renal diabetes can be a prelude to diabetes and develop into true diabetes based on renal diabetes.

2. Secondary renal glucose and urine: common to primary renal glucosuria, secondary to chronic interstitial nephritis, multiple myeloma and other organic kidney damage, most patients with tetanus have a renal Diabetes, renal glucosuria in pregnant women is another common clinical phenomenon, women with late pregnancy and childbirth are associated with varying degrees of lactoseuria, which is a qualitative difference between physiological phenomena and renal glucose and urine, some secondary kidneys Sexual diabetes is often associated with other renal tubular dysfunction and has a typical clinical manifestation of the primary disease.

Renal diabetes test

1. Urine flow test: sucrose oxidase test for urine test can significantly increase glucose, diet containing hot card 103J / kg (30cal / kg) or carbohydrates accounted for 50% of total calories, 24h urine glucose quantitation > 500mg More often, it can reach 100g/24h, most of them are 5~30g/24h, urine phosphorus, amino acid, uric acid, bicarbonate and other uric acid tests are normal.

2. A large amount of galactose can be detected.

3. The glucose tolerance test is normal or slightly fluctuating.

4. Fasting blood glucose is normal, glomerular filtration rate of chrysanthemum clearance is 148 ~ 158ml / (min · 1.73m2) sugar clearance rate and glomerular filtration rate is almost equal, intravenous glucose to increase blood glucose concentration to 261 After ~342mg/dl (14.48~18.98mmol/L), the blood glucose clearance rate did not change.

Regular B-ultrasound and X-ray examination.

Diagnostic differentiation of renal diabetes

diagnosis

Primary renal diabetes can be diagnosed based on clinical manifestations and family history.

1. Clinical diagnosis (according to Marble standard):

(1) Normal or low blood glucose, normal glucose tolerance curve (oral glucose tolerance test is normal or slightly fluctuating).

(2) urine sugar positive, generally daily urine sugar amount <30g, continuous appearance of urine sugar without fluctuations in diet.

(3) Glucose reducing substances can be detected in urine.

(4) Carbohydrate accumulation and utilization are normal.

(5) There is a positive family history, no diabetes and a history of previous kidney disease.

2. Qualitative diagnosis: firstly, it should exclude the overflowing diabetes and non-glucose glucosuria caused by hyperglycemia, the urine urinary benzene diphenol test is positive, the pentose urinary urine urinary hydrochloric acid dicarboxytoluene reaction positive, lactose urine, galactose urine and nectar The heptose can be determined by chromatography on urine paper.

3. The etiology of renal glucosuria: secondary renal diabetes, such as Fanconi syndrome, Lowe syndrome and other clinical manifestations of kidney disease, the basic disease is characterized by clinical diagnosis To provide an important basis, the small intestinal glucose-galactose malabsorption syndrome in primary renal glucosuria can also be diagnosed according to its unique clinical manifestations. The diagnosis of benign familial renal glucosuria is important for family history investigation.

4. Judgment of the severity of renal glucosuria: The usual practice is to measure the amount of urinary glucose excretion in 24h. When the blood glucose is at physiological concentration, the more the urinary glucose excretion in 24h, the worse the reabsorption of renal tubular sugar; Urine sugar excretion is also affected by glomerular filtration rate. Therefore, when renal function declines, 24h urine glucose excretion can not reflect the severity of renal diabetes. A reasonable method is to measure glomerular filtration. Rate and glucose clearance rate, and then calculate the ratio of glucose clearance to glomerular filtration rate. The higher the ratio, the worse the renal tubular glucose reabsorption function, and the ratio is close to 1.0 in O-type renal glucosuria.

Differential diagnosis

1. Diabetes: These patients often have elevated fasting blood glucose and decreased glucose tolerance, but there are a few cases where renal glucoseuria and diabetes are present in the same individual.

2. Other reasons for diabetes:

(1) pentose urinary: urinary Bial reaction (dicarboxytoluene hydrochloride) is positive, and can be determined as pentose urinary.

(2) Fructose urine: The urine Selivanoff reaction (resorcinol) is positive and can be determined as fructose.

(3) Lactose urine, galactose urine, mannose heptose urine: can be determined by chromatography on urine paper.

3. Other secondary diseases such as chronic nephritis, pyelonephritis, multiple osteomyelitis, Fanconi syndrome, Lowe syndrome and pregnancy can have diabetes, but the primary disease is clear and not difficult to identify.

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