A 5-month-old intact female English springer spaniel had been evaluated by the referring veterinarian for lethargy, decreased
appetite, vomiting, and weight loss of one week's duration. A complete blood count (CBC) had revealed no abnormalities. Abnormal
serum chemistry profile results were elevated blood urea nitrogen and creatinine concentrations, hypercalcemia, hyperphosphatemia,
hyponatremia, and hyperkalemia (Table 1).
Table 1: Selected Serum Chemistry Profile Results
Treatment had included intravenous lactated Ringer's solution (26 ml/kg every 12 hours as a bolus) and injections of aminopentamide
hydrogen sulfate (0.03 mg/kg every 12 hours), enrofloxacin (0.59 mg/kg every 12 hours—note that enrofloxacin is contraindicated
in small- and medium-breed dogs between 2 and 8 months of age), and penicillin G (19,480 U/kg every 12 hours). The puppy's
clinical signs had improved slightly after 24 hours of hospitalization, at which time it had been discharged to the owner.
The referring veterinarian had tentatively diagnosed renal failure due to a genetic or congenital problem. A therapeutic renal
diet had been the only treatment prescribed.
PHYSICAL EXAMINATION AND DIAGNOSTIC TESTING
Six days later (day 7), the puppy was referred to our hospital because of progression of clinical signs and for evaluation
of possible renal failure. On presentation, the patient weighed 14.9 lb (6.8 kg) and was laterally recumbent and about 8%
dehydrated. The puppy had a poor body condition, a dry and unkempt coat, bilateral mucopurulent ocular discharge, and waxy
debris in both ears. The puppy's rectal temperature was 99.7 F (37.6 C), its heart rate was 150 beats/min, and its respiratory
rate was 32 breaths/min. Its mucous membranes were pale-pink.
We suspected hypoadrenocorticism and performed a CBC, a urinalysis, a serum chemistry profile, and an ACTH stimulation test.
The CBC results revealed no abnormalities. The lack of a stress leukogram in this critically ill animal supported our suspicion
of hypoadrenocorticism. The urinalysis results were normal, including a urine specific gravity of 1.020 (adult dog reference
range = 1.015 to 1.050). Puppies older than 4 weeks of age have urine specific gravity measurements similar to those of healthy
adult dogs.1 However, urine specific gravity is expected to be increased in the face of hypovolemic shock, even in a puppy.
Serum chemistry profile results revealed mild azotemia and hyponatremia and severe hyperkalemia, hypercalcemia, and hyperphosphatemia
(Table 1, day 7). The sodium:potassium ratio in this puppy was 16.6. A sodium:potassium ratio < 24 is highly correlated with hypoadrenocorticism.2 We also considered primary hyperparathyroidism and secondary hyperparathyroidism due to renal failure as differential diagnoses
for the hypercalcemia. However, because of the owner's financial limitations and our strong suspicion of hypoadrenocorticism,
we did not measure ionized calcium and parathyroid hormone concentrations. Furthermore, the dog had been receiving a high-quality
commercial puppy food and had no known ingestion of toxins such as rodenticides, psoriasis drugs, or excess vitamin D or calcium.