Renal Tubular Acidosis

Renal tubular acidosis (RTA) is a group of disorders in which the kidney tubules fail to keep the blood's acid level normal even though overall filtering function is preserved. Either acid is not excreted properly in the far part of the tubule, or bicarbonate is lost in the near part, or a hormone signal is defective.

There are three main types: distal (type 1), proximal (type 2) and hyperkalaemic (type 4). Type 1 and 2 usually cause low potassium; type 4, the most common in adults, causes high potassium. RTA is treatable, and treatment prevents stones, bone disease and poor growth.

Symptome

• Often none; found as low bicarbonate on blood tests
• Tiredness and muscle weakness, sometimes episodes of paralysis from low potassium
• Recurrent kidney stones or calcium deposits in the kidneys (nephrocalcinosis) in distal RTA
• Bone pain, rickets or osteomalacia
• Poor growth, vomiting and dehydration in infants and children
• Excessive thirst and urination
• Hearing loss in some inherited forms

Ursachen und Risikofaktoren

Distal RTA may be inherited or acquired through autoimmune disease, particularly Sjogren syndrome and lupus, and drugs such as amphotericin and lithium. Proximal RTA is usually part of Fanconi syndrome, caused by inherited conditions such as cystinosis in children or by myeloma, tenofovir, ifosfamide or carbonic anhydrase inhibitors such as acetazolamide and topiramate in adults. Type 4 results from low aldosterone or resistance to it: diabetic kidney disease, urinary obstruction, and drugs such as ACE inhibitors, spironolactone, trimethoprim, heparin, NSAIDs and calcineurin inhibitors.

Wie es diagnostiziert wird

• Blood bicarbonate, chloride and potassium: Show a normal anion gap acidosis with low or high potassium.
• Urine pH and urine anion gap: A urine pH persistently above 5.5 during acidosis suggests distal RTA.
• Acid loading or furosemide-fludrocortisone test: Specialist tests for incomplete distal RTA.
• Bicarbonate loading test: Measures bicarbonate wasting in proximal RTA.
• Urine glucose, phosphate, amino acids and low molecular weight protein: Detect Fanconi syndrome.
• Kidney ultrasound: Looks for nephrocalcinosis and stones.
• Autoimmune, myeloma and genetic tests: Search for the underlying cause.

Behandlungsmöglichkeiten

• Alkali replacement: Sodium bicarbonate or potassium citrate daily; modest doses in distal RTA, much larger doses in proximal RTA.
• Potassium supplements: Needed in types 1 and 2, often as potassium citrate, which also reduces stone formation.
• Treating the cause: Stopping the responsible drug, treating Sjogren syndrome or myeloma, relieving obstruction.
• Measures for type 4: Low-potassium diet, loop or thiazide diuretics, potassium binders, and sometimes fludrocortisone.
• Vitamin D and phosphate: For bone disease in Fanconi syndrome.
• Stone management: Hydration and urological treatment of existing stones.

Wenn es dringend ist

Sudden severe muscle weakness or paralysis, palpitations, fast deep breathing, or a vomiting, lethargic infant need emergency care locally, as potassium and acid levels may be dangerous.

Reisen nach Türkiye zur Behandlung

Once diagnosed, RTA is managed with daily tablets and periodic blood tests at home. A visit can be worthwhile for the diagnostic work-up when the cause is unclear, including specialised urine testing, imaging, autoimmune screening and genetic testing for children with suspected inherited forms. Make sure results reach your own doctor, who will adjust the alkali dose over time.

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