History: Boris, an 8yr old MN Malamute, was on medication for hypothyroidism which was well controlled. He was presented for PU/PD which had been noticed only very recently by the owners. History was otherwise unremarkable.
Physical examination: Unremarkable overall. HR 74, RR16, BCS 4/9, mms pink, CRT 1.5seconds, good synchronous pulses. No detectable abnormalities on thoracic auscultation or abdominal palpation. No palpable lymphadenopathy.
Bloods and urinalysis: Mild elevation in total calcium; rest of biochemistry (including SDMA) wnl; electrolytes wnl; haematology unremarkable; USG 1.014; sediment and dipstick unremarkable. Follow on ionised calcium confirmed true hypercalcemia.
What are your differentials and what would you do next?
Differential diagnoses for canine hypercalcemia:
- Malignancy (most commonly lymphoma, anal adenocarcinoma and multiple myeloma)
- Primary hyperparathyroidism
- Renal disease
- Hypervitaminosis D (e.g. psoriasis cream, rodenticide, jasmine) or hypervitaminosis A
- Granulomatous disease
- Osteolytic skeletal lesions (e.g. osteomyelitis, osteosarcoma)
- Excess phosphate in diet
Hypercalcemia can also be a normal finding in young growing dogs and total calcium can be increased artefactually with hyperalbuminemia.
Investigations: Cost was a concern so tests had to be selected carefully. Results from the routine bloods made renal disease or Addisons unlikely. There was no history of toxin exposure and no palpable lymphadenopathy or anal mass. Globulins were normal (usually high with multiple myeloma). Routine imaging of the thorax and abdomen was unremarkable other than several small calculi in the bladder. Urinary calculi are more common with primary hyperparathyroidism and the dog is also likely to be systemically ‘well’ compared to many of the other differentials. Ultrasound of the parathyroid region identified a 2cm hypoechoic nodule. Elevated PTH levels with concurrent elevated ionised calcium are the gold standard for diagnosis of hyperparathroidism but had to be omitted in this case due to cost. Additionally they require special handling (freezing and courier transport to the lab) and are only run weekly at specialist laboratories so turnaround for results can be over a week.
The nodule was surgically excised and the small calculi were flushed out via urinary catheterisation. Calcium levels were monitored post operatively as they can drop but he was discharged without complications and the signs resolved.
This case demonstrates how it is still possible to reach a diagnosis and carry out effective treatment in cost constrained cases by considering history, physical examination, basic test findings and good quality imaging. In practice diagnostic procedures are often omitted due to many reasons such as cost, owner fears, lack of expertise and concurrent disease complications but the risks of these omissions should always be discussed thoroughly with the owners. In this case surgery was undertaken based on a presumptive diagnosis and it was important that the owners were fully aware of this.