Hyponatremia and metabolic alkalosis in a foal with gastroesophageal reflux: a case report

A foal with a history of diarrhea and fever was presented to the Equine Clinic of the University of Cordoba for acute onset of abundant serous nasal discharge. On endoscopic examination the oesophagus was found to be atonic and ulcerated, the cardia was permanently open and the stomach showed extensive ulceration. In addition, the nasal discharge was identified to have a gastric origin (gastroesophageal reflux). The electrolyte and acid-base profiles showed marked hyponatremia (99 mEq/l) and metabolic alkalosis (pH = 7.46, Strong Ion Difference = 50 mEq/l). The foal was also uremic (plasma creatinine = 12.6 mg/dl). Although the foal experienced an improvement in its hydroelectrolytic status after treatment with 7.5% NaCl for 36 h, the owner requested eutha- nasia. The foal described here developed severe hyponatremia and hyposmolarity but, contrary to most reported cases, showed metabolic alkalosis instead of metabolic acidosis. Another interesting feature of this case is the lack of overt neurologic signs in the face of extreme hyposmolarity. The paucity of neurologic signs in this foal may have been influenced by slow instauration of hyponatremia, concurrent azotemia, or acid-base status.