Renal tubular acidosis

　　Renal tubular acidosis is a metabolic acidosis caused by dysfunction of the proximal and/or distal renal tubules. The degree of metabolic acidosis varies depending on the location and severity of the damaged renal tubules, but common manifestations include varying degrees of metabolic acidosis.

　　The location and severity of renal tubular acidosis, which leads to damage in the renal tubules, vary according to clinical manifestations. However, common manifestations include varying degrees of metabolic acidosis. If not treated in time, it can lead to renal rickets or osteomalacia; bone calcification and/or kidney stones, and a few patients may have deafness, sudden fractures, renal colic with hematuria, and loose teeth. Severe renal function damage can lead to serious conditions such as uremia.

　　The degree of metabolic acidosis varies depending on the location and severity of the damaged renal tubules, but common manifestations include varying degrees of metabolic acidosis.

　　1,ⅠType

　　This is the most common type in clinical practice. Like type 2, genetic cases occur in infancy and childhood, and can also occur in early adulthood, with secondary cases more common. Children with this disease are often found due to unsteady gait, which is related to osteomalacia in patients. The most common clinical manifestation in adult patients is recurrent hypokalemic paralysis, which usually occurs at night or after exertion. The symptoms range from mild weakness in the limbs to severe cases where the limbs lose the ability to move independently, except for the head and neck, which can even cause respiratory muscle paralysis and difficulty breathing. The attack can last for several hours or 1-2 days, and mild cases can recover spontaneously; severe cases require intravenous potassium chloride infusion to recover. The mechanism of hypokalemic paralysis is directly related to the potassium ion gradient inside and outside the cell, and is not related to the absolute level of potassium in the plasma. Due to increased calcium excretion in urine and secondary hyperparathyroidism, renal calcification and urinary tract stones are more likely to occur, the latter can cause renal colic, and is prone to recurrent pyelonephritis. Due to skeletal mineralization disorders, children are prone to rickets and incomplete fractures, and adults may develop osteomalacia. Children with the disease also have growth and development delays, which may be caused by acidosis leading to a lack of IGF-1 receptors in cartilage.

　　2,ⅡType

　　Genetic cases are more common in children, with a family history, and are autosomal dominant inheritance. Secondary cases can also occur in adults, with散发性和继发性 cases more common than familial and genetic cases. The main clinical manifestations are metabolic acidosis, hypokalemia, and myopathy. Children lose nutrients such as glucose, amino acids, and phosphates in the urine, so they have growth and development delays, malnutrition, and rickets. Hypokalemia can cause muscle weakness and fatigue, and hypokalemia can be seen on an electrocardiogram, but paralysis due to hypokalemia is rare, which may be related to this type of 'limited' renal tubular acidosis.

　　3,ⅢType (mixed type)

　　The main clinical manifestation of this type of patient is metabolic acidosis, normal blood potassium levels, so there is no muscle weakness and hypokalemic paralysis. Some clinical manifestations of patients with types 1 and 2 may occur.

　　4,ⅣType

　　Patients, in addition to hyperchloremic metabolic acidosis, have the main clinical characteristics of hyperkalemia, decreased blood sodium levels, and some patients may develop orthostatic hypotension due to reduced blood volume.

　　In addition to the above clinical manifestations, patients with secondary renal tubular acidosis also show clinical manifestations of the primary disease.

　　Renal tubular acidosis is a metabolic acidosis caused by dysfunction of the proximal and/or distal renal tubules, which is not uncommon in clinical practice. The severity of clinical symptoms varies, with mild cases showing no symptoms and severe cases presenting with polyuria, thirst, polydipsia, pain in the bones and muscles. During examination, hyperchloremic acidosis (but without azotemia) can be found, along with increased urinary alkali concentration. There are also cases of renal calculi or renal calcification of unknown etiology. Early treatment has a good prognosis, while late seekers of medical attention still have an unoptimistic prognosis. Currently, symptomatic treatment for this disease can still alleviate symptoms and allow for normal living and work. Early diagnosis and treatment can prevent the progression of the disease and avoid adverse outcomes.

　　In summary, it is necessary to actively treat the primary disease and complications. If osteopathy or severe calcium deficiency occurs, calcium and active vitamin D preparations can be given.

　　Renal tubular acidosis is generally diagnosed by combining various examination methods, and the specific examination methods are as follows.

　　1, Urine examination

　　The urine pH value of type 1 patients is often above 5.5, often increased to 7 (even though there is obvious blood acidosis), and incomplete type patients only show this condition after ammonium chloride loading test, and type 2 patients only have an increased urine pH value when there is severe acidosis, and the urine pH value can be

　　2, Blood biochemistry

　　All types of patients have a decrease in blood pH, only incomplete type 1 patients can have blood pH within the normal range, blood CO2 binding capacity is the same as blood pH, type 1 and 2 blood potassium decreases, type 3 is normal, type 4 increases, and there may be secondary increase in blood ammonia in severe distal renal tubular acidosis. Miller et al. reported that in a baby with severe distal renal tubular acidosis, the kidneys may synthesize more ammonia, but it does not excrete from the urine, causing ammonia to reflux into the blood circulation and causing an increase in blood ammonia.

　　3, Loading test

　　For incomplete type 1 renal tubular acidosis, ammonium chloride loading test can be performed to help with diagnosis. The test method is to take 2g of ammonium chloride orally, 3 times a day, for 5 consecutive days after fasting from acidic or alkaline drugs. If the blood pH value decreases and the urine pH value still cannot drop below 5.5, it can be diagnosed as incomplete type 1 renal tubular acidosis. After oral calcium chloride 0.2g/kg, if the urine pH value cannot drop below 5.5 within 5 hours, it indicates that there is a disorder in acidification, and it can be diagnosed as incomplete type 1 renal tubular acidosis. Within 2 hours, intravenous infusion of 400ml of sodium bicarbonate, if the concentration of HCO3- in the urine is high, it supports the diagnosis of type 2 renal tubular acidosis.

　　4, ECG examination

　　In hypokalemia, there is ST segment depression, T wave inversion, and the appearance of U waves.

　　5, X-ray bone examination

　　Osteoporosis is obvious, mainly in the lower limbs and pelvis, and some may present with fractures. The radionuclide bone scan shows sparse and uneven radionuclide absorption.

　　6, Other

　　The urinary citrate/creatinine ratio in patients with complete or incomplete type 1 renal tubular acidosis is all below 2.5. The measurement of the CO2 gradient in urine and blood (urine and blood CO2 gradient

　　Patients with renal tubular acidosis should eat foods rich in calcium or vitamin D. The diet of patients should be light and easy to digest, with more fruits and vegetables, a reasonable diet, and attention to adequate nutrition. In addition, patients also need to pay attention to avoid spicy, greasy, and cold foods.

　　There is currently no cure for hereditary renal tubular acidosis, and gene therapy is under study.

　　For secondary renal tubular acidosis caused by other diseases, the primary disease should be treated first. If the primary disease can be cured, the renal tubular acidosis can also be cured accordingly. For those who cannot be cured of the primary disease, the following symptomatic treatments can only be taken like hereditary renal tubular acidosis.

　　Treatment for type 1 renal tubular acidosis: First, alkali supplements are used to correct acidosis. The compound citrate mixture is preferred as an alkali, consisting of 140g of citric acid, 100g of sodium citrate, and water to 1000ml (also known as Shohl mixture). The dose is 20 to 30 ml per time, three times a day. This mixture, in addition to correcting acidosis, also has the effect of preventing the formation of urinary tract stones. Potassium salt is supplemented to correct hypokalemia. Such as potassium chloride tablets, potassium chloride sustained-release capsules, potassium citrate, etc.

　　Treatment for type 2 renal tubular acidosis: Because the patient loses a lot of sodium bicarbonate, it is advisable to supplement sodium bicarbonate, selecting different doses according to the severity of the condition, generally 8 to 12g per day, taken in divided doses. Supplementing bicarbonate can correct metabolic acidosis, but the excretion of bicarbonate in urine also increases, increasing the loss of urinary potassium, so potassium should be supplemented at the same time. In severe acidosis, sodium intake should be restricted, and hydrochlorothiazide should be taken orally to increase the excretion of Cl- (decreasing the reabsorption of Cl-), reducing the loss of HCO3- from urine, with a dose of 25 to 50 mg, three times a day. Generally, 10% potassium citrate should be taken orally to correct hypokalemia, with a dose of 20 to 30 ml, three times a day. When supplementing sodium bicarbonate (bicarbonate sodium), it can increase the loss of urinary potassium. Those with increased excretion of calcium and phosphates should supplement phosphates, such as taking 20 ml of phosphate buffer solution every 6 hours. At the same time, vitamin D preparations should be taken to increase intestinal calcium absorption and avoid the occurrence of secondary hyperparathyroidism, which can further increase the loss of urinary phosphates. Active vitamin D preparations can be tried for severe osteopathic patients.

　　Treatment for types 3 and 4 renal tubular acidosis mainly involves supplementing mineralocorticoid, which not only corrects hyperchloremic metabolic acidosis but also corrects hyperkalemia. The commonly used drug is fludrocortisone. The dose is 0.2 to 0.5 mg per time, once a day. Furosemide can increase the excretion of Na, Cl-, K, and H, so it can also be used to treat patients with type 4 renal tubular acidosis. It can enhance the efficacy when used in combination with fludrocortisone.