Distal renal tubular acidosis in a three-year-old warmblood gelding

In horses distal renal tubular acidosis has so far only been described in s ix cases. Out from the four different forms of renal tubular acidosis obser ved in man only the proximal and the distal forms are known in horses. The present case a three year-old warmblood gelding was depressed, had anorexia , ataxia, an impaction of the small colon and in addition to the clinical p athological findings were metabolic acidosis (pH 7,034; pCO(2) 4,09 kPa; bi carbonate 7,6 mmol/l; base deficit -21,8 mmol/l), hyperchloraemia (124 mmol /l), anion gap 10,4 mmol/l. Urine pH was 8. Due to these findings and the l ack of clinical symptoms which may cause metabolic acidosis renal tubular a cidosis was diagnosed. Differentiation into proximal or distal renal tubula r acidosis was carried out by using ammonium chloride loading. In this test the kidney failed to reduce the pH-value in the urine less than 6,9 within two to five hours which allowed to diagnose the distal form of renal tubul ar acidosis.