Prevalence of incidental bullae and blebs was low and none developed spontaneous pneumothorax

Significance of incidentally identified bullae and blebs on thoracic computed tomography and prevalenceof subsequent pneumothorax in dogs

Donough Healy DVM, MRCVS 1 | Laura Ballarini DVM, MRCVS 2 |Petra Agthe CertVDI, DipECVDI, MRCVS 3 |Matteo Cantatore DVM, PhD, DipECVS, MRCVS 1 |Alison L. Moores BVSc (Hons), Cert SAS, DECVS, FRCVS

Background
Pulmonary bullae and blebs (PBBs) are air-filled spaces within or on the surface of lung tissue, which may predispose dogs to spontaneous pneumothorax (SP). Although PBBs are associated with SP in dogs, the risk of incidental PBBs leading to SP has not been well-studied. This study aimed to determine the prevalence of incidental PBBs in dogs undergoing thoracic CT for unrelated reasons and evaluate the risk of subsequent SP.

Methods
A retrospective analysis of 2,221 thoracic CT studies performed on dogs between 2013 and 2019 was conducted. Dogs with incidentally identified PBBs were included if they had no concurrent pneumothorax, severe pulmonary disease, or incomplete CT studies. PBBs were classified by size (bullae >10 mm; blebs ≤10 mm) and location (parenchymal vs. pleural). Owners were contacted via questionnaire or phone to assess follow-up outcomes, including the development of SP. Statistical analyses explored associations between PBB prevalence, signalment, and reasons for CT imaging.

Results
Prevalence: PBBs were identified in 30 of 2,178 CT studies (1.37%). A total of 60 PBBs were observed, with most lesions classified as blebs (58.3%) and located in the caudal lung lobes (66.6%).

Signalment: Dogs with PBBs were significantly older (median age: 10.5 years) than those without (median age: 8.2 years; p = 0.001). Common breeds included Springer Spaniels, Labrador Retrievers, and Cocker Spaniels.

Clinical Follow-Up: No dog developed clinical signs of SP during a median follow-up of 1,255 days (range: 147–2,363 days). One dog died suddenly, but SP could not be ruled out due to lack of post-mortem.

Associations: PBBs were more commonly identified during metastatic screening (p = 0.006) but were not associated with persistent cough (p = 0.931).

Limitations
The study was limited by its retrospective nature and small sample size of dogs with PBBs. Variability in CT slice thickness (1.5–5 mm) may have affected PBB detection. The absence of repeat CT imaging precluded analysis of PBB size progression over time. Additionally, follow-up data relied on owner reports, which may have led to underreporting of clinical signs.

Conclusions
The prevalence of incidental PBBs in dogs was low, and none of the identified cases developed confirmed SP during follow-up. These findings suggest that prophylactic surgical removal of incidental PBBs is not warranted in most cases. However, veterinarians and owners should remain aware of the potential risk of SP in dogs with PBBs, even though the overall likelihood appears minimal.

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