Pain related syndrome of inappropriate antidiuretic hormone secretion in a kitten

A 2-month-old domestic shorthair kitten was presented for evaluation of weakness, gait abnormalities, and signs of pain after trauma. On admission, the patient was found laterally recumbent with obvious gait abnormalities: difficulty rising from sitting and marked unilateral left hind limb lameness. On orthopedic examination, severe pain, crepitations, and swelling of the left hind limb were detected. Results of the first diagnostic work-up were all consistent with hyponatremia, hypochloremia and a Salter-Harris type I fracture.

The kitten initially received isotonic fluids, analgesia, and antiemetic treatment. Twelve hours after admission, the analgesic plan was considered insufficient, and the general patient's condition worsened, showing severe mental depression. Blood and urine samples were collected for a more in-depth diagnostic evaluation; the patient showed worsening hyponatremia (113 mmol/L; [RR: 146,2-156,2]), severe plasma hypoosmolality (218.2 mOsm/kg; [RR: 287-307 mOsm/kg]), high natriuresis (Na: 74.9 mmol/L; [RR: <40 mmol/L]), and urinary hyperosmolality (630 mOsm/kg; [RR: <150 mOsm/kg]). Based on these new clinical findings syndrome of inappropriate antidiuretic hormone (SIADH) secretion was diagnosed.

Emergency treatment with hypertonic saline was then instituted, a constant rate infusion of 3% hypertonic saline infusion to increase plasma sodium was initiated and a loop diuretic, furosemide (1 mg/kg/IV), was administered at 12-hour intervals to induce diuresis. Discharge occurred 4 days after admission as the patient was clinically stable and the hyponatremia progressively resolved. To the author's knowledge this is the first report of a kitten developing pain related SIADH associated to orthopedic trauma.