Sterile nodular panniculitis in dogs: how to diagnose it
5-year-old Dachshund with several soft subcutaneous nodules on the trunk, 1 to 3 cm in size, some fistulated and draining a yellowish, oily fluid. It has mild fever and lethargy.
What is the most appropriate next diagnostic step?
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A. 4 mm punch biopsy of the surface of a nodule
A small punch barely reaches the subcutaneous fat, where the lesion lies; the sample is often non-diagnostic.
B. Cytology of the exudate: if no organisms are seen, start prednisolone
Cytology shows pyogranulomatous inflammation, but failing to see organisms does not rule out mycobacteria, fungi or Nocardia, which may be scarce. Immunosuppressing such an infection would worsen it.
C. Excisional biopsy of an intact nodule for histopathology and tissue culture (bacteria, mycobacteria and fungi)
Correct. Sterile panniculitis is a diagnosis of exclusion: it requires a deep sample including fat, with special stains and negative tissue cultures. Choose a non-fistulated nodule to avoid contamination.
D. Empirical antibiotic for 6 weeks and assess the response
It delays diagnosis and does not cover mycobacteria or fungi. If the lesions are sterile, they will not respond.
lightbulb Key takeaway
Before diagnosing idiopathic sterile panniculitis rule out infections, foreign bodies, injection reactions, trauma and panniculitis associated with pancreatitis or pancreatic neoplasia. Idiopathic forms usually respond well to prednisolone; a single nodule may be cured by excision.
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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.