12-year-old castrated male Domestic Shorthair cat

Found as a stray, now tachypnea and central vestibular signs

  • 3 major findings — Mixed pulmonary pattern characterized by:
  1. Diffusely distributed, ill-defined nodules of variable size and shape (not all round)
  2. Some indistinct alveolar foci are seen; most conspicuous is seen in the ventral periphery of the left cranial lung (best example is seen dorsal to the 4th sternebra on right lateral & asymmetric opacity on VD)
  3. Heterogeneously distributed bronchial markings, right middle lung collapse & hyperinflation
  • Minor points were awarded for some discussion on the accessory lung lobe opacification.

Examiner Comments:

All candidates identified the nodules, but the descriptions less commonly indicated that the nodules were oblong shaped, rather than round/spherical. Successful candidates considered pulmonary parenchymal infiltrate for the dorsally irregular soft tissue seen dorsal to the 4th sternebra, as well as noting this structure is too caudal for a sternal lymph node.  A cranial mediastinal mass was considered an incorrect designation of a normal radiographic feature as abnormal. Widening is not seen on the ventrodorsal projection.

Candidates were in the minority that identified and described thoracic hyperinflation and bronchial markings (<25%).  In contrast, all candidates identified the alveolar pattern in the right middle lung.  There was poor discrimination between right middle lung collapse versus increased volume; the committee agreed that this was a “classic” appearance of lobar collapse associated with hyperinflation and chronic airway disease in feline patients.  Most candidates, in attempting to link primary pulmonary neoplasia with the nodules (i.e. presumed these were metastases), incorrectly debated infiltration of primary neoplasm into bronchus or lung causing this appearance. This is an example of how candidates struggled to fit the pulmonary changes together to fit a neoplastic process.

  • Diffuse inflammatory/infectious (toxoplasmosis, fungal, FIP mycoplasma) vs neoplasia (mets/carcinoma).
  • Concurrent chronic or chronic-active lower airway disease (i.e. asthma) with secondary middle lung lobe atelectasis. Atelectasis of the accessory lung lobe was the correct interpretation, but none were penalized for considering an atypical diaphragmatic hernia or fat accumulation. Likely unrelated condition to current presentation based on extent of bronchial markings.

Examiner Comments:

The majority of candidates ranked metastatic neoplasia over infectious inflammatory processes based on the age of the patient and suggested the CNS signs were metastatic neoplasia. This would be uncommon for carcinoma (most commonly listed as top differential for neoplasia) and even for lymphoma.  Those selecting neoplasia as a primary differential diagnosis did not seem to consider the atypical shape of the nodules.  There seemed to be a clear relationship between correctly prioritizing infectious etiologies and those candidates that reviewed the history prior to or during the synthesis process.  The most common neurologic disease in feline patients with concurrent pulmonary disease that was given by candidates was fungal.  Toxoplasma was uncommonly listed, which is the disease process represented in this case.

Approximately 50% of candidates that did not consider certain important details of the history (stray cat, CNS signs) failed the case, as the history was important to complete inclusion of differential diagnoses. Unsuccessful case synthesis completely excluded infectious and inflammatory causes.  The concern is that patients could be euthanized based on the level of confidence of candidates who concluded only neoplasia.  This case is an example of the trend mentioned in the general comments (i.e. to give one differential diagnosis or strongly prioritize a disease in cases where there were two or unrelated disease processes).

  • BAL and/or sampling via ultrasound-guidance for peripheral lesions
  • Work up vestibular signs – MRI
  • Candidates were penalized if CT was suggested simply to “better define pulmonary disease/lesions”; they earned partial credit if CT was justified (ie. “could try ultrasound first, but may need CT if a lesion is not peripheral enough to be identified or BAL inconclusive”).

Examiner Comments:

The best strategy given by candidates started with obtaining a cellular sample in the least invasive method possible. Since most candidates did not recognize unstructured interstitial and bronchial patterns, many selected FNA of the nodules over BAL. This was not penalized.  If candidates did not recognize significance of CNS disease, the second management point (neurocranium MRI) was not mentioned.