The renal tubular acidosis (RTA) is a acidosis and electrolyte imbalance due to an impaired renal hydrogen ion secretion (Type 1), a disturbed Bicarbonatresorption (type 2) or abnormal aldosterone or reaction (type 4). Type 3 is extremely rare and is not discussed here. Patients may be asymptomatic, or they show symptoms and signs of electrolyte imbalance or fall into a chronic kidney disease. Diagnosis is based on characteristic changes in urine pH and electrolytes in response to provocative testing. The therapy corrects the pH and electrolyte imbalances by means of alkaline substances and electrolytes, rarely medication.
RTA as a group defined by disorders in which the secretion of hydrogen ions or the reabsorption of filtered is disturbed bicarbonate. This leads to chronic metabolic acidosis with a normal anion gap. Most is a hyperchloraemia before, and secondary disorders may (often) and calcium (rare-see table: Some features of the various forms of renal tubular acidosis *) other electrolytes such as potassium concern.
The renal tubular acidosis (RTA) is a acidosis and electrolyte imbalance due to an impaired renal hydrogen ion secretion (Type 1), a disturbed Bicarbonatresorption (type 2) or abnormal aldosterone or reaction (type 4). Type 3 is extremely rare and is not discussed here. Patients may be asymptomatic, or they show symptoms and signs of electrolyte imbalance or fall into a chronic kidney disease. Diagnosis is based on characteristic changes in urine pH and electrolytes in response to provocative testing. The therapy corrects the pH and electrolyte imbalances by means of alkaline substances and electrolytes, rarely medication. RTA as a group defined by disorders in which the secretion of hydrogen ions or the reabsorption of filtered is disturbed bicarbonate. This leads to chronic metabolic acidosis with a normal anion gap. Most is a hyperchloraemia before, and secondary disorders may (often) and calcium (rare-see table: Some features of the various forms of renal tubular acidosis *) other electrolytes such as potassium concern. Chronic RTA is often associated with a structural damage of the renal tubules and can lead to chronic kidney disease. Some features of the various forms of renal tubular acidosis * Feature Type 1 Type 2 Type 4 Incidence Rare Very Rare Common mechanism Impaired hydrogen ion excretion Impaired Bicarbonatresorption reduction in aldosterone secretion or- activities plasma bicarb onate (mmol / l) often <15, random <10 12-20 Normally Typically> 17 plasma potassium As a rule low, but tends to normalize with alkalization In general, low and by alkalization further reduced bulk urine pH> 5.5> 7, when plasma bicarbonate is normal <5.5 when plasma bicarbonate is reduced (eg. As <15 mmol / l) <5.5 * Type 3 is very rare. Type 1 (distal) RTA type 1 is a decreased secretion of hydrogen ions in the distal tubule, which leads to a permanently elevated pH (> 5.5) and to a systemic acidosis. The plasma bicarbonate is usually <15 mEq / l, and often are a hypokalemia, hypercalciuria and reduced Citratexkretion ago. Hypercalciuria is the primary abnormality in some familial cases, with calcium-induced tubulointerstitial damage cause a distal RTA. Nephrocalcinosis and nephrolithiasis are possible complications of hypercalciuria and the Hypocitraturie when the urine is relatively alkaline. This syndrome is rare. Sporadic cases occur most often in adults and may be primary (almost always women) or secondary. Familial cases manifest themselves usually first in childhood and are usually autosomal dominant. The secondary type 1 RTA can be caused by drugs, kidney or verschiedenn diseases: autoimmune disease with hypergammaglobulinemia, particularly Sjögren's syndrome or RA kidney nephrocalcinosis medullary sponge kidney Chronic Obstructive uropathy drugs (especially amphotericin B, ifosfamide, and lithium), cirrhosis sickle cell anemia potassium levels may occur in patients with chronic obstructive uropathy or sickle cell anemia be high. Type 2 (proximal) RTA type 2 denotes an impairment of bicarbonate reabsorption in the proximal tubules, which causes a urine pH> 7, if the plasma bicarbonate concentration is normal, and a urine pH <5 , if the plasma bicarbonate concentration is already decimated by the progressive loss. 5 This syndrome can occur as part of a generalized dysfunction of the proximal tubules and patients can have an increased excretion of glucose, uric acid, phosphate, amino acids, citrate, calcium, potassium and protein. Osteomalacia or osteopenia (including rickets in children) can develop. The mechanisms hypercalciuria, Hyperphosphaturie, changes in vitamin D metabolism and secondary hyperparathyroidism can count on. The type 2 RTA is very rare and occurs most often in patients with the following: Fanconi syndrome Leichtkettennephropathie due to multiple myeloma using different drugs are (usually acetazolamide, sulfonamides, ifosfamide, outdated tetracycline or streptozocin) Sometimes other causes such as vitamin D deficiency, chronic hypocalcemia with secondary hyperparathyroidism, renal transplantation, heavy metal poisoning and other inherited diseases (eg. as fructose intolerance, Wilson's disease, okulozerebrorenales syndrome [Lowe syndrome], cystinosis) into question. Type 4 (generalized) RTA type 4 is caused by a lack of aldosterone or Aldosteronempfindlichkeit the distal tubules. Since aldosterone promotes sodium absorption in exchange for potassium and hydrogen, there is a reduced Kaliumexkretion, which in turn causes hyperkalemia and reduced acid excretion. Hyperkalemia can reduce the ammonia excretion, and contribute to metabolic acidosis. Urine pH is normally in accordance with the serum pH (typically <5.5 when a Serumazidose present). Plasma bicarbonate is usually> 17 mmol / l. This disorder is the most common form of RTA. They typically occur sporadically due to a disturbance in the renin-aldosterone-renal axis (hyporeninämischer hypoaldosteronism) ago. Diabetic nephropathy Chronic interstitial nephritis Other factors that may contribute to a type 4 RTA include: use of ACE inhibitors aldosterone synthase type I or II deficiency use of angiotensin II receptor antagonists: Chronic kidney disease in which usually as a result of diabetic nephropathy, or chronic interstitial nephritis Congenital adrenal hyperplasia, in particular 21-hydroxylase deficiency critical illness use of cyclosporine use of heparin (including low molecular weight heparins) HIV nephropathy (due to, possibly partially, infections with Mycobacterium avium complex or cytomegalovirus) interstitial kidney damage (e.g., as a result of SLE, obstructive uropathy or sickle cell anemia) Potassium-sparing diuretics (eg. B. amiloride, eplerenone, spironolactone, triamterene) use of NSAIDs Obstructive uropathy Other drugs (such. As pentamidine, trimethoprim) Secondary Adrenal insufficiency Pseudohypoaldosteronism (Type I or II) volume expansion (eg. As acute glomerulonephritis or chronic kidney disease) symptoms and complaints The RTA runs usually asymptomatic. Severe electrolyte disturbances are rare but can be life threatening. Nephrolithiasis and nephrocalcinosis are possible, especially in type 1-RTA. Signs of ECF volume reduction can develop through the urine fluid loss in connection with the electrolyte excretion in a type 2 RTA. People with type 1 or type 2 RTA may have symptoms and complaints of hypokalemia with muscle weakness, and hyporeflexia paralysis. Einerknöchernen involvement (z. B. bone pain and osteomalacia in adults and rickets in children) may occur in patients with type 2 and sometimes in type 1-RTA. A type-4 RTA runs usually asymptomatic with little acidosis, but cardiac arrhythmias or paralysis, if hyperkalemia is severe. Diagnosis is suspected in patients with metabolic acidosis with normal anion, or with unexplained hyperkalemia serum and urine pH, electrolyte level and osmolalities Often tests after stimulation (z. B. with ammonium chloride, bicarbonate, or a loop diuretic) The suspected RTA is patients with unexplained metabolic acidosis (low Plasmabicarbonat and low blood pH) with a normal close anion. A Type 4 RTA should be suspected in patients who have a persistent hyperkalemia without apparent cause, such as potassium supplements, potassium-sparing diuretics, or chronic kidney disease. A ABGA is performed to confirm a RTA and to exclude a respiratory alkalosis as a cause of a compensatory metabolic acidosis. Electrolytes, urea, creatinine and urine pH are determined in all patients. depending on which form is suspected of RTA further investigations and sometimes provocative tests are performed: A type 1 RTA is secured by a urinary pH, which remains in systemic acidosis of> 5.5. Acidosis can occur spontaneously or by an acid load test (administration of ammonium chloride, 100 mg / kg p.o.) are induced. Healthy kidneys reduce urine pH within 6 h after the onset of acidosis to <5.2. carried a diagnosis of type 2 RTA by measurement of urine pH and the fractional Bicarbonatausscheidung during a BicarbonatInfusion (sodium bicarbonate, 0.5-1.0 mEq / kg / h i.v.). In Type 2, the urine pH value increased to> 7.5 and fractional excretion of bicarbonate is> 15%. Because i.v. can contribute to hypokalemia bicarbonate, potassium supplements should be given in sufficient quantities prior to infusion. Type 4 RTA is confirmed by previous conditions which could be associated with type 4 RTA, chronically elevated potassium and normal or slightly reduced bicarbonate. In most cases, plasma renin activity and aldosterone concentration are low and cortisol is normal. Therapy varies depending on the type often alkali-therapy treatment of accompanying abnormalities in terms of potassium, calcium and phosphate metabolism The treatment consists in the correction of the pH and electrolyte balance by administering alkaline substances. An unsuccessful RTA therapy slows the growth in children. Alkaline substances such as sodium bicarbonate, potassium bicarbonate or sodium citrate can help to achieve a relatively normal plasma bicarbonate concentration (22-24 mEq / l). Potassium citrate, if a persistent hypokalemia exists, or because sodium increases the excretion of calcium, be replaced in the presence of calcium stones. A vitamin D (z. B. ergocalciferol, 800 IU po 1 time daily) and oral calcium substitution (elemental calcium 500 mg po 3 times daily, for. Example, as calcium carbonate 1250 mg po 3 times daily) may also be required to reduce skeletal deformities by osteomalacia or rickets. Type 1 RTA adults obtained sodium bicarbonate or sodium citrate 0.25-0.5 mEq / kg p.o. every 6 h. This dose may be adjusted as the child grows. In children, a total daily dose of up to 2 mEq / kg every 8 h necessary. A potassium intake is usually not necessary if dehydration and secondary aldosteronism corrected with bicarbonate therapy werden.Typ-2-RTA A normal plasma bicarbonate levels can not be restored, but the bicarbonate replacement should exceed the acid load of food z. B. (sodium bicarbonate 1 meq / kg po every 6 h in adults or 2-4 mEq / kg every 6 h in children) to maintain serum bicarbonate at about 22-24 mEq / L, as to be risked by lower levels of growth disorders , On the other side of the Kaliumbicarbonatverlust increased by extreme Bicarbonatersatz in urine. Therefore citrate can be substituted instead of sodium bicarbonate. They are also better tolerated. Potassium supplements or potassium citrate may be required to be hypokaliämisch by the administration of sodium bicarbonate in patients. This is not recommended in patients with normal or high serum potassium levels. In difficult cases, treatment with low-dose hydrochlorothiazide 25 mg po stimulate two times a day the proximal Tubulustransportfunktionen. In cases of a generalized proximal Tubulusstörung hypophosphatemia and bone disorders to normalize the plasma phosphate concentration with phosphate and vitamin D supplementation behandelt.Typ-4-RTA The hyperkalemia is with volume increase, dietary potassium restriction and kaliumausschwemmenden diuretics treated (Furosemide, 20-40 mg po titrated 1 times a day or 2 times per day until an effect is obtained). Alkalization is often unnecessary. Some patients need a Mineralokortikoidersatztherapie (fludrocortisone, 0.1-0.2 mg po 1 times a day, often higher in hyporeninemic hypoaldosteronism). However, a Mineralokortikoidersatz should be used with caution because it can worsen an existing hypertension, heart failure or edema. Conclusion A renal tubular acidosis (RTA) is a group of disorders in which the secretion of hydrogen ions or the reabsorption of filtered is disturbed bicarbonate. This leads to chronic metabolic acidosis with a normal anion gap. RTA is usually formed by abnormal aldosterone or reaction (Type 4) or, more rarely due to reduced hydrogen ion secretion (Type 1) or disturbed absorption bicarbonate (type 2). RTA should be suspected if the patient metabolic acidosis with a normal anion gap or an unexplained hyperkalemia have BGA and serum electrolytes, urea nitrogen and creatinine and urine pH must be checked. Other tests should be performed to confirm the type of RTA (eg., Acid load test for Type 1, Bicarbonatinfusion for type 2). The treatment should be carried out by means of alkali-treatment and measures for the correction of low serum potassium in type 2 and potassium restriction or potassium consuming diuretics in type 4 RTA; other electrolytes are administered as required.