Right Middle Lobe Hyperlucent? CT Keys Lobar Emphysema—Multicenter JVIM Study

Imaging findings in 14 dogs and 3 cats with lobar emphysema

Harry Warwick; James Guillem; Daniel Batchelor; Tobias Schwarz; Tiziana Liuti; Sally Griffin; Erin Keenihan; Marie-Laure Theron; Swan Specchi; Giuseppe Lacava; Jeremy Mortier

Background

Lobar emphysema is a rare cause of respiratory compromise in dogs and cats, arising from expiratory bronchial collapse and air trapping that hyperinflates an affected lobe and compresses adjacent structures. Prior veterinary literature consisted mainly of case reports; this study characterizes patient demographics and imaging features across a multicenter cohort, and contrasts radiography with CT.

Methods

Retrospective review (2008–2018) from six referral hospitals of animals diagnosed with lobar emphysema by thoracic radiography and/or CT. Images were reread by an ECVDI diplomate and resident. Recorded variables included affected lobes, attenuation (HU) on CT, bronchial changes (collapse/obstruction/bronchiectasis), vascular caliber, mediastinal shift, thoracic wall/diaphragmatic deformation, and concurrent lesions. Clinical data, treatment, and histopathology (when available) were extracted.

Results

Seventeen animals met criteria (14 dogs, 3 cats). Dyspnea (59%) and cough (35%) predominated; 65% were <3 years old. The right middle lung lobe was most frequently involved (≈71%); multilobar disease occurred in 41%. Congenital lobar emphysema (CLE) was suspected in 82%, while acquired causes (eg, neoplasia, diaphragmatic hernia) were identified mainly in older patients. On CT, the affected lobe(s) were always identifiable; supplying bronchi were collapsed in 13/14 CT cases, and feeding vessels were small in 13/14. Mean attenuation was lower in emphysematous vs normal lung (about −949 HU vs −741 HU). Common accompanying features included atelectasis of adjacent lobes (13/14), mediastinal shift, thoracic wall and diaphragmatic deformation; pleural effusion and pneumothorax were each noted in a subset. Radiography often suggested the diagnosis but less reliably localized the exact lobe or bronchial lesion. Ten animals underwent surgery (mostly right middle lobectomy); 8/10 survived to discharge. Histopathology (9 cases) confirmed CLE in 8 (bronchial cartilage hypoplasia recorded in 4) and pulmonary adenocarcinoma in 1.

Limitations

Retrospective design with incomplete clinical/laboratory/histologic data in some cases; heterogeneity in imaging protocols (breath-hold/ventilation status not standardized); few animals had both modalities for direct comparison; in cases without histology, underlying pathology could not be definitively assigned.

Conclusions

Lobar (often right-middle) or multilobar emphysema should be considered in young dogs and cats with dyspnea or cough. CT improves lobe localization, depicts bronchial collapse/obstruction and secondary effects, and aids surgical planning; radiographs are useful but less specific. In older animals, actively search for acquired extramural bronchial compression (eg, neoplasia, hernia). Surgical lobectomy, when indicated, was frequently associated with short-term survival to discharge.

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