Renal tubular acidosis

Renal tubular acidosis is a group of disorders in which kidney tubules fail to regulate acid or bicarbonate effectively, causing metabolic acidosis despite relatively preserved glomerular filtration.

Type 1 renal tubular acidosis: A distal acidification defect that limits urinary hydrogen-ion secretion and causes metabolic acidosis. This distal subtype characteristically produces alkaline urine, low potassium, and a risk of kidney stones.
Metabolic acidosis: A primary reduction in blood bicarbonate that lowers blood pH when respiratory compensation is insufficient. Renal tubular acidosis is one cause of this acid–base disorder, usually with a normal anion gap.
Sjögren syndrome: An autoimmune disease that primarily affects moisture-producing glands and can involve other organs. It is a recognized acquired cause of distal renal tubular acidosis.
Chronic kidney disease: A persistent abnormality of kidney structure or function that affects health for at least three months. Unlike classic renal tubular acidosis, advanced disease can cause acidosis as filtration declines.
Type 2 renal tubular acidosis: A proximal bicarbonate-reabsorption defect that causes metabolic acidosis, often with low potassium. This subtype wastes bicarbonate, especially before blood bicarbonate reaches a lower steady-state level.
Normal anion gap metabolic acidosis: Metabolic acidosis in which the measured serum anion gap remains within its reference range. This biochemical pattern narrows the differential toward tubular bicarbonate loss or impaired acid excretion.
Amphotericin B: An antifungal medication that can damage kidney tubular membranes and cause electrolyte disturbances. Tubular toxicity from this drug can produce a distal acidification defect.
Diarrhea: Frequent passage of loose or watery stools, which can cause fluid and bicarbonate loss. It causes normal-anion-gap metabolic acidosis without a primary kidney tubular defect.
Type 4 renal tubular acidosis: A disorder of reduced aldosterone activity or response that impairs ammonium excretion and causes hyperkalemic metabolic acidosis. Its high potassium distinguishes it from the more common potassium-losing tubular forms.
Hypokalemia: A lower-than-normal concentration of potassium in the blood. Types 1 and 2 commonly cause potassium loss, shaping symptoms and treatment choices.

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