Renal tubular reabsorption disorder

Introduction The glomerulus filters 180 liters of liquid per day, about 99% is reabsorbed by the renal tubules, such as water, potassium, sodium, glucose, amino acids, uric acid, phosphate, bicarbonate and other substances required by the body, damage and necrosis of the renal tubules. Diabetic nephropathy and the like can cause renal tubular reabsorption dysfunction. Renal tubular epithelial cells transport the solute inverse concentration difference or potential difference in the tubule fluid to the perivascular tissue night, the solute in the tubule fluid is diffused by the potential difference, and the water is infiltrated by the osmotic pressure difference. , the process of transferring from the lumen to the perivascular tissue fluid.

Cause

Renal tubular damage, renal tubular dysfunction, acute tubular necrosis, diabetic nephropathy and other tubular damage leading to renal tubular reabsorption dysfunction. Renal tubular epithelial cells transport the solute inverse concentration difference or potential difference in the tubule fluid to the perivascular tissue night, the solute in the tubule fluid is diffused by the potential difference, and the water is infiltrated by the osmotic pressure difference. , the process of transferring from the lumen to the perivascular tissue fluid.

an examination

Related inspection

Urine amino acid nitrogen sodium xylenol determination HCO3-reabsorption test ammonium chloride load test

(1) Free water removal: Free blood clearance (CH2O) was used to estimate renal tubular damage by measuring the osmolality of blood and urine.

(2) Sodium excretion fraction (FENa): Reference value <1%. To determine the ability of renal tubules to retain sodium. When dehydration, due to the increase of renin and aldosterone, the renal tubules retain sodium as much as possible, and the sodium excretion fraction is generally less than 1%. When acute tubular necrosis occurs, sodium reabsorption capacity decreases, and sodium excretion decreases. The score increased to more than 1%.

(3) Determination of urine sugar: normal blood sugar, glucose in the urine is usually caused by tubular damage caused by renal tubular reabsorption dysfunction, that is, renal glucosuria.

(4) Analysis of amino acids in urine: The amino acids filtered by the glomerulus are normally reabsorbed by the renal tubules. When the renal tubule is damaged, the amino acid in the urine can be increased.

(5) N-acetyl--D glucosaminidase (NAG) (reference value: upper limit: 507 U/L). It is widely found in body fluids, red blood cells, white blood cells and platelets of various tissues and organs. It is an acidic hydrolase in lysosomes. The most abundant kidneys are in the organs. The NAG in urine is mainly derived from renal proximal tubular epithelial cells. Is a sensitive indicator of tubular damage. Increased: acute and chronic nephritis, renal failure, epidemic hemorrhagic fever, toxic nephropathy, renal tumor, renal transplant patient rejection, is an early damage indicator of diabetic nephropathy.

(6) 2-microglobulin (2M) (reference value: serum: 77 to 186 g/L). 2-2-microglobulin is a lower molecular weight protein that is widely present on all cell surfaces. It is a subunit of human leukocyte antigen (HLA's) that is almost completely reabsorbed after glomerular filtration, and urinary 2 - Increased microglobulin reflects renal tubular dysfunction, and increased serum 2-microglobulin may be associated with increased synthesis or decreased glomerular function. Studies have shown that serum 2-microglobulin and serum creatinine have A good correlation, the correlation coefficient is 0.985, the ratio of 2-microglobulin to creatinine can be used to judge the prognosis of kidney transplantation; the normal ratio of 2 M/Cr ranges from 0.25 to 2.5; when 2 M/Cr<2.5, The 2-microglobulin is less than 4 mg/L, indicating that the renal function has been restored after transplantation; when 2M>2.5, the result is poor. In addition, it can also monitor malignant tumors, such as myeloma, lymphoma, chronic lymphocytic leukemia and other B lymphocyte malignant tumor serum 2-microglobulin also increased.

(7) Urinary trehalase (URT) (reference value: 4 to 19 mol/H-1?G-1). Urinary trehalase is an extracellular enzyme produced in the proximal tubular and small intestinal mucosal epithelial cells. The urinary trehalase is mainly derived from proximal tubular epithelial cells. Its activity can be used as an early, sensitive and specific marker for brush border damage in proximal tubular epithelial cells.

Differential diagnosis

Differential diagnosis of renal tubular reabsorption:

1, acute tubular necrosis: acute tubular mecrosis (ATN) is the most common type of acute renal failure, accounting for about 75% to 80%. It is a clinical syndrome that occurs due to renal ischemia and/or nephrotoxicity caused by various causes of renal function and progressive decline. Mainly manifested as progressive azotemia caused by a significant decrease in glomerular filtration rate, as well as imbalance of water, electrolyte and acid-base balance caused by renal tubular reabsorption and excretion. According to the reduction of urine volume or not, it is divided into two types: oliguria (animal) and non-oliguric. Early treatment of dialysis in severely treated patients can significantly reduce the incidence of infection, bleeding, and cardiovascular complications. The prognosis is related to the primary disease, age, early and late diagnosis and treatment, and whether multiple organ failure is combined. Some causes of acute tubular necrosis can be prevented, most of which are reversible. After timely treatment, renal function can be fully recovered within weeks or months.

2, renal glucosuria: renal glucosuria refers to normal blood glucose levels and diabetes, patients with fasting blood sugar and glucose tolerance are normal. Various congenital or acquired causes (such as familial renal glucosuria and various renal tubular acidosis) cause renal proximal convoluted tubule damage, resulting in renal tubular reabsorption of glucose, and glomerular filtration rate is still normal Diabetes is present due to a decrease in the threshold of renal sugar, often accompanied by reabsorption disorders such as amino acids, bicarbonates, and uric acid. However, some patients with renal diabetes can be converted to true diabetes.

3. Diabetic nephropathy: Urinary nephropathy (DN) is a particularly common and troublesome diabetic complication. In other words, diabetic nephropathy is one of the most serious complications of diabetes and the leading cause of end-stage renal disease. Diabetic nephropathy is the main microvascular complication of diabetes, mainly refers to diabetic glomerulosclerosis, a glomerular lesion with vascular damage. Most of the early asymptomatic, blood pressure can be normal or high.

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