Whipworms mimicking Addison's: hyponatraemia and hyperkalaemia
4-year-old crossbreed with large-bowel diarrhoea with fresh blood, weakness and weight loss. Faecal flotation shows numerous Trichuris vulpis eggs. ACTH stimulation: post-stimulation cortisol 14 µg/dL.
| Parameter | Result | Reference |
|---|---|---|
| Sodium | 131 mmol/L | 144–156 mmol/L |
| Potassium | 6.4 mmol/L | 3.5–5.5 mmol/L |
| Na:K ratio | 20.5 | > 27 |
| Creatinine | 1.1 mg/dL | 0.5–1.5 mg/dL |
What is the most appropriate approach?
chevron_right Show answer and explanation
A. Start lifelong mineralocorticoids, because the electrolytes confirm Addison's disease
A low Na:K ratio is not diagnostic: with a normal ACTH stimulation test, hypoadrenocorticism is ruled out and hormone treatment is not indicated.
B. Treat the whipworm infection with an effective anthelmintic and correct the electrolytes; they should normalise once the parasites are cleared
Correct. Heavy whipworm infections can cause hyponatraemia and hyperkalaemia (pseudohypoadrenocorticism) through colonic disease. With normal post-ACTH cortisol, treatment is antiparasitic, with fluids if needed, and repeated because of the long Trichuris life cycle.
C. Consider the eggs an incidental finding and look for kidney disease
The creatinine and clinical picture do not suggest kidney disease, and a heavy Trichuris burden with colonic diarrhoea explains the whole picture.
D. Repeat the ACTH stimulation test in a month without treating yet
Delaying treatment adds nothing: the likely cause has been identified and is treatable.
lightbulb Key takeaway
Hyponatraemia and hyperkalaemia do not equal Addison's disease: they also occur with whipworms, severe gastrointestinal disease, repeated effusions or uroabdomen. Always confirm with an ACTH stimulation test before lifelong treatment.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.