[Renal tubular acidosis (type 2) in a Friesian mare].

The study revolves around a 2-year-old Friesian mare that had been showing signs of tiredness, leading to a clinical examination. The researchers discovered a condition known as type 2 renal tubular acidosis through blood biochemistry and urine tests, which was then treated with sodium bicarbonate and potassium chloride, resulting in improved blood values.

Identifying the Problem

• A 2-year-old Friesian mare was brought for examination due to lethargy persisting for several weeks.
• A blood biochemistry test showed normal levels of creatinine (136 mumol.L-1) and urea nitrogen (6.1 mmol.L-1) in the plasma, ruling out abnormalities in these parameters.
• A notable finding, however, was severe metabolic acidosis, with the venous pH being 7.154, well below the physiological pH level (typically around 7.4), and a low bicarbonate concentration of 13 mmol.L-1.
• The base excess was high, -15.3 mmol.L-1, indicating an acid-base imbalance in the body. Similarly, the venous pCO2 measured 5.1 kPa, suggesting abnormal carbon dioxide levels in the blood.

Further Investigations

• The researchers found normal plasma sodium levels (135 mmol.L-1) but detected slightly elevated plasma chloride levels (113 mmol.L-1). There was also a presence of hypokalaemia (2.9 mmol.L-1), suggesting deficient potassium levels in the blood.
• Investigation of the mare’s urine showed a specific gravity of 1.040 (which is relatively concentrated urine) and a pH of 5 (significantly less than the usual pH of horse urine, which is around 7 to 7.5).

Diagnosis and Treatment

• These findings indicated type 2 renal tubular acidosis, a rare medical condition in horses, characterized by failure of the kidneys to normally acidify urine, leading to metabolic acidosis.
• The mare was treated with sodium bicarbonate, which was given as a 4.2 percent solution (3.2 mol in total) and supplemented with additional bicarbonate (125 g) and potassium chloride (100 g) administered orally. This treatment helped replenish bicarbonate and potassium levels and correct the acid-base balance.
• The blood values of the mare returned to normal within three days of initiating the treatment, indicating the success of the therapeutic measures.