Objective—To compare quantitative densitometric
computed tomography (CT), morphometric, and histologic
data of normal lungs in dogs with similar parameters
obtained after induction of an acute inflammatory
response and determine whether CT densitometry
correlated with histopathologic changes.
Animals—6 healthy adult dogs.
Procedure—After initial CT, 1 mL of 0.1M hydrochloric
acid (HCl) and 3 mL of autologous blood were instilled
into the right middle (RM) and caudal segment of the
left cranial (LCCd) lung lobes, respectively. Immediately
and 24 hours after instillation, CT was repeated. At 24
hours, dogs were euthanatized and lungs were fixed
and sampled for morphometric and histologic evaluation.
The CT data were compared with lung morphology
and morphometry by use of unpaired t tests.
Comparison with lungs from control dogs was performed
using Spearman rank correlation coefficients.
Results—Mean Hounsfield units (HU) from control
and baseline HU from experimental dogs were identical.
Immediately after instillation of HCl or blood, there
was increased attenuation in both lobes. Autologous
blood initially induced severe changes that almost
completely resolved at 24 hours; HCl induced severe
changes at 24 hours. Significant increases in percentage
of parenchymal airspace and alveolar diameter
resulted in decreased surface area-to-volume ratio in
lobes receiving HCl. Histologic scores were significantly
higher in the RM lobe, compared with controls.
Conclusions and Clinical Relevance—Computed
tomography attenuation correlated well with histomorphometry
and histologic findings in this model.
Lung lesions after autologous blood were transient
and of limited severity. Lesions induced by HCl were
severe; alterations in morphometric and histologic
parameters were reflected in CT attenuation measurements.
(Am J Vet Res 2004;65:1114–1123)