Renal tubular acidosis (RTA) is characterized by altered renal tubular function resulting in hyperchloremic metabolic acidosis. The purpose of the study was to describe RTA in 16 horses. No breed or sex predilection was found. The mean age at onset of the disease was 7 years of age. The type of diet had no apparent effect on development of RTA. The most common clinical signs were depression, poor performance, weight loss, and anorexia. Initial blood work revealed a marked hyperchloremic metabolic acidosis in all horses and a compensatory respiratory response in most horses. Sixty-three percent (10/16) of the horses had some evidence of renal damage or disease. Initial treatment consisted of large amounts of sodium bicarbonate given intravenously and orally for the prompt correction of the acidosis. Response to treatment was largely dependent on the rate of sodium bicarbonate administration. Long-term oral supplementation with NaHCO 3 was required for the maintenance of normal acid-base status in individual horses. Recurrence of RTA was noted in 56% (9/16) of the horses. Horses with evidence of renal disease had multiple relapses. RTA should be considered as a differential diagnosis in horses with vague signs of depression, weight loss, and anorexia. The pathogenesis of RTA in horses remains uncertain, but prompt recognition and early aggressive intravenous sodium bicarbonate therapy followed by long-term oral supplementation seem to be important to successful management.Key words: Hyperchloremic metabolic acidosis; Renal disease; Sodium bicarbonate.
Metabolic acidosis is characterized by a decrease in pH as the result of increased endogenous production or accumulation of acid, or by the loss of bicarbonate via the gastrointestinal or urinary tract. The most common causes of metabolic acidosis with an increased anion gap (AG) include lactic acidosis, ketoacidosis, and hypovolemic shock.1 Other causes of metabolic acidosis include ingestion of compounds such as salicylate, methanol, ethylene glycol, or paraldehyde, which result in the accumulation of exogenous anions.
2Hyperchloremic metabolic acidosis with a normal AG is associated with bicarbonate loss from diarrhea or renal causes, such as renal tubular acidosis (RTA).1 Hyperchloremia develops consequent to enhanced renal conservation of chloride in the face of bicarbonate loss.1 RTA, characterized by abnormal tubular function, has been described in humans, dogs, cats, and horses. [3][4][5][6][7][8][9][10][11] In humans, RTA may be a primary condition inherited as an autosomal dominant trait.12 Further, RTA may develop secondary to a variety of conditions such as kidney disease, obstructive uropathies, nephrocalcinosis, cirrhosis, drug-or toxin-induced nephropathies, and autoimmune diseases.12 RTA has also been reported as a complication of inhalation of volatile organic solvents containing toluene such as acrylic paints, glues, adhesives, paint thinners, varnishes, and shoe polishes.
12-13Three types of RTA have been described in humans: types I, II, and IV.12...