Renal tubular acidosis in children

Introduction to renal tubular acidosis in children Renal tubular acidosis (RTA) is caused by the reabsorption of HCO3- by hydrogen ions and/or proximal tubular epithelium in distal renal tubular epithelial cells, causing high chloride metabolic acidosis, potassium, A group of clinical syndromes characterized by electrolyte imbalance such as sodium and calcium. The clinical manifestations are characterized by high chloride metabolic acidosis, renal calcification and kidney stones with normal anion gap, which can be divided into primary and secondary according to the cause. Hairy. The primary is mostly caused by congenital genetic defects, and secondary is secondary to a variety of kidney diseases, collagen diseases and drug-induced kidney damage. RTA is also known as Lightwood syndrome, Albright type III syndrome, Butier syndrome, congenital hyperchloric acidosis, renal calcinosis, infant calcinosis, and Lightwood-Butier-Albright syndrome. basic knowledge Sickness ratio: 0.0001% Susceptible people: young children Mode of infection: non-infectious Complications: dehydration, hyponatremia, kidney stones, renal colic

Causes of renal tubular acidosis in children

(1) Causes of the disease

Divided into primary and secondary.

Congenital factors (25%):

It belongs to autosomal recessive genetic disease. It is also reported to be a congenital far-renal unit defect of autosomal dominant inheritance. It is often caused by infancy, and sporadic cases can occur at any time.

Disease factors (35%):

Can be caused by a variety of causes, secondary to congenital genetic diseases such as sickle cell anemia, Marfansydrome (EarersDanlossynohome); secondary to various autoimmune diseases, such as systemic systemic Lupus erythematosus, hyperimmune globulinemia and chronic active hepatitis; abnormal calcium and phosphorus metabolism caused by various causes, such as hyperparathyroidism, hyperthyroidism, etc.; may also be caused by drugs such as vitamin D poisoning, poisons Poisoning, in addition, pyelonephritis, obstructive kidney disease can also lead to DRTA.

(two) pathogenesis

According to the damaged part of the renal tubule and its pathophysiological basis, it is divided into 4 types: type I is distal renal tubular acidosis (DRTA), also known as classical renal tubular acidosis, type II is proximal renal tubular acid. Proximal renal tubular acidosis (PRTA), type III is a mixture of type I and type II, also known as mixed type. Type IV renal tubular acidosis is due to insufficient secretion of congenital or acquired aldosterone or insensitive to aldosterone response by renal tubules. Metabolic poisoning and hyperkalemia caused by each type can be divided into primary or secondary renal tubular acidosis.

Prevention of renal tubular acidosis in children

Preventive measures refer to other methods for the prevention of birth defects, and prevention should be carried out from pre-pregnancy to prenatal:

1. Premarital medical examination plays an active role in preventing birth defects: the size of the effect depends on the examination items and contents, mainly including serological examination (such as hepatitis B virus, treponema pallidum, HIV), reproductive system examination (such as screening for cervical inflammation) ), general physical examination (such as blood pressure, electrocardiogram) and asking about the family history of the disease, personal medical history, etc., do a good job in genetic disease counseling.

2. Pregnant women should avoid harmful factors as far as possible: including away from smoke, alcohol, drugs, radiation, pesticides, noise, volatile harmful gases, toxic and harmful heavy metals, etc., in the process of antenatal care during pregnancy, systematic screening of birth defects is required. Including regular ultrasound examination, serological screening, etc., if necessary, a chromosome examination.

Once an abnormal result occurs, it is necessary to determine whether to terminate the pregnancy; the safety of the fetus in the uterus; whether there is sequelae after birth, whether it can be treated, how to prognose, etc., and take practical measures for diagnosis and treatment.

Pediatric renal tubular acidosis complications Complications, dehydration, hyponatremia, kidney stones, renal colic

The symptoms may exist alone or in combination with other multiple renal tubular dysfunction, may be dehydration, slow growth, hyponatremia, high chloride metabolic acidosis, refractory rickets, renal calcification, kidney stones, renal colic , polyuria, chronic renal insufficiency and associated with renal tubules and interstitial diseases.

Symptoms of renal tubular acidosis in children Common symptoms Lack of bone pain, polyuria, kidney, dull pain, nausea, kidney calcification, loss of appetite, kidney stones, constipation, nausea and vomiting

1. Primary proximal RTA (type II): proximal tubules are deficient in bicarbonate reabsorption, more common in boys, slow growth, symptoms of acidosis, symptoms of hyponatremia, loss of appetite, often nausea , vomiting, fatigue, constipation, dehydration and other symptoms, the renal threshold of bicarbonate is about 18 ~ 20mmol / L or less, when the ammonium chloride load test, can discharge acidic urine with pH <5.5.

2. Primary distal RTA (type I): distal renal tubular secretion of H+ dysfunction, resulting in urine can not be acidified, but high chloride metabolic acidosis, autosomal dominant inheritance, girls more common (about 70%), poor growth and development, intractable rickets, can express bone pain and duck gait, kidney calcification, kidney stones, renal colic, polydipsia, polyuria, dehydration, hypokalemia, hyperchloremic metabolic acid Poisoning with alkaline or weakly acidic urine, ammonium chloride load test, urine pH can not be reduced to 5.5 or less is a significant difference from the proximal RTA.

3. Mixed type (type III): It has the characteristics of type I and type II. It is found in infants. The symptoms appear early, and symptoms can appear in one month after birth.

4. Type IV: characterized by persistent hyperkalemia and renal-derived hyperchlorine acidosis, with some degree of chronic renal insufficiency and associated with renal tubules and interstitial disease, reduced renin secretion, aldosterone secretion Defects, renal acidification dysfunction and type II, urinary bicarbonate excretion is often 2% to 3%, and no other proximal tubular dysfunction, pediatric patients can reduce acidosis with age.

Examination of renal tubular acidosis in children

1. Biochemical examination : five low and two high characteristics, namely low blood phosphorus, hypokalemia, low carbon dioxide binding, low serum pH, low blood calcium (or normal), high blood chlorine, high serum alkaline phosphatase.

2. Determination of blood potassium: If hyperkalemia can diagnose type IV RTA, if the blood potassium is low or normal, the urine pH should be determined and further tested as sodium bicarbonate, neutral phosphate test and sodium sulfate test.

3. Determination of urinary ammonium : the purpose is to exclude proximal renal tubular acidosis and non-renal hyperchlorinated acidosis, such as urinary ammonium <50mmol / d, should consider long-term renal tubular acidosis.

4. X- ray examination : Bone X-ray showed active rickets, osteoporosis, delayed bone age, or associated with pathological fractures, aseptic necrosis of the femoral head, urinary calculi and renal calcification.

5.B ultra-examination : Kidney B-ultrasound may have diffuse injury of renal cortex, renal dysplasia, hydronephrosis, diuretic ureteral dilatation or renal calcium deposition.

6. Ultrasound examination:

The renal medullary echo of type I children is significantly increased. The hyperechoic cones are arranged radially around the renal sinus, with clear boundaries with the cortex, bright, fine-point echoes inside, no shadows or light shadows behind, cortical areas and echoes of the collection system. Normal, color Doppler shows that the early renal vascular tree can still be regularly displayed to the renal interlobular arteries and veins. As the disease progresses, the accumulation of sediment in the renal medulla gradually forms a pressure on the blood vessels, mainly involved. The segmental artery and the interlobular artery, the blood flow below the arcuate artery is reduced, and the blood supply in the cortical area is star-shaped, and no renal calcium accumulation occurs in the type II kidney.

Diagnosis and diagnosis of renal tubular acidosis in children

Patients with the following conditions should consider RTA: 1 unexplained hypokalemia symptoms, and repeated attacks; 2 unexplained growth retardation, and can exclude vitamin D deficiency rickets and dwarfism; 3 unexplained acidosis, by ordinary alkaline agents Treatment is not easy to correct, and urine pH is neutral or weakly acidic; 4 unexplained multiple times, polyuria and dehydration, and urine specific gravity and urine sugar are normal, except for diabetes insipidus and diabetes; 5 refractory dehydration acidosis, there are In the case of further, bicarbonate titration, urinary calcium, urine phosphorus determination for diagnosis.

1. Diagnosis of remote RTA

In addition to clinical symptoms, mainly based on the degree of acidosis and urine pH is not proportional, urine pH is higher than 6; glomerular filtration function is normal; urea nitrogen and plasma creatinine are normal, difficult to diagnose can do simple ammonium chloride load test : Oral ammonium chloride 0.1 / kg, served within 1h, 3 ~ 8h after the collection of urine, such as urine pH can not be reduced to 5.5 or less positive, but children do not try this test as much as possible, so as not to aggravate acidosis and cause accidents.

The symptoms must be differentiated from chronic renal failure, severe dehydration acidosis, pituitary or renal diabetes insipidus, and respiratory alkalosis.

2. Diagnosis of proximal RTA

Hyperchlorine acidosis, when mild acidosis, plasma HCO3- concentration is higher than the renal threshold (17 ~ 20mmol / L), urine pH > 6, but under acid load conditions (ammonium chloride load test) urine pH can be <5.5, when the concentration of plasma HCO3- is increased, K+ is increased from the urine. In the past, the reason for polydipsia was caused by hypokalemia caused by urinary enrichment. In recent years, it was found that after drinking hypokalemia, polydipsia was still more Exist, so consider the possibility of involvement of tubulointerstitial damage.

The differential diagnosis is mainly related to chronic renal failure, severe dehydration acidosis, pituitary dwarfism and renal diabetes insipidus.

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