On examination, the dog was quiet but clinically normal. His blood glucose concentration, however, was low at 26 mg/dl (reference range, 70-125 mg/dl). All other serum chemistry results (including serum sodium and potassium were normal. Radiographs of the chest and abdomen were unremarkable. The owner has been quizzed at length about possible xylitol ingestion, but there is no history of possible ingestion.
We hospitalized the dog for observation and started a 5% dextrose drip overnight. This morning, the blood glucose was still quite low (only 47 mg/dl) after being off dextrose for about an hour. I continued the glucose drip (raised it to a 10% drip), and the blood glucose concentrations ranged from 41 to 70 mg/dl throughout the day. He is eating well and alert on the IV glucose supplementation.
My rule outs are the following intoxications or medical disorders:
- Xylitol ingestion
- Atypical Addison's (the serum electrolytes and Na:K ratio were normal)
- Insulinoma (insulin-secreting pancreatic islet cell tumor)
- Portosystemic shunt
Any other thoughts, suggestions for diagnostics? Anything I am missing?
You have the correct list of differential diagnoses and are working your way through the list properly. I'd agree with not fasting the dog — I'd just do a random bile acid measurement to first see it that's abnormal.
If this dog has an insulinoma, we have to remember that IV administration of dextrose may stimulate secretion by the pancreatic tumor. Insulin release post-hyperglycemia often results in rebound hypoglycemia, which necessitates additional dextrose administration and leads the clinician into a cyclical hyperglycemia/hypoglycemia "chase" which can be difficult to terminate.
In this cases, it an be really helpful to just use glucagon instead. Glucagon for injection (1 mg vial) is reconstituted according to the manufacturer's instructions with supplied diluent, then added to 1000 ml of 0.9% NaCl. The 1000 ng/ml solution is administered intravenously as a constant rate infusion (CRI) with the use of a syringe infusion pump. The glucagon CRI is initially given as a bolus of 50 ng/kg, then administered at a rate of 10 to 15 ng/kg/min. The dose may need to be increased up to 40 ng/kg/min as needed to maintain euglycemia.
I've put the dog on a glucagon constant rate infusion and it's been working great to maintain the blood glucose concentration in the normal range in the hospital!
The dog's resting serum cortisol concentration was normal at 3.2 μg/dl, so Addison's disease appears highly unlikely. My serum insulin and bile acid results still pending.
The owner has been internet investigating and he told me that his dog has eaten a birch limb/stick last week. I read that xylitol is derived from hardwoods such as birch — Is there any way the xylan from the birch could be metabolized to xylitol in the dog?
You're right, the normal serum cortisol (>2.0 μg/dl) rules out Addison's disease.
As far as xylitol toxicity is concerned, I did some research myself and found that birch wood itself doesn't contain xylitol so that's unlikely to be the cause of the hypoglycemia. And this would be especially true since it was consumed a week ago, and you wouldn't expect continued hypoglycemia if the problem was due to xylitol toxicity.
|Abdominal ultrasound showing |
multiple hypoechoic masses in liver
Based on the poor prognosis and lack of response to diazoxide, the owners elected euthanasia. Multiple pancreatic and hepatic nodules were identified at necropsy; histopathology confirmed beta cell islet cell neoplasia with metastasis to the liver.
Final Diagnosis: Insulinoma (insulin-secreting carcinoma of pancreas), producing hypoglycemia.
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