The evaluation of non-anesthetic computed tomography for detection of pulmonary parenchyma in feline mammary gland carcinoma: a preliminary study

Abstract

Background: Thoracic radiography in awake cats is a common procedure for the evaluation of pulmonary metastasis in feline mammary gland carcinoma (MGC). However, due to poor sensitivity, computed tomography (CT) is progressively taking its place. To perform CT in animals, general anesthesia is normally preferred but can cause lung atelectasis, affecting lung interpretation. Besides, MGC is often found in senile cats that are concurrently affected with other diseases, increasing anesthetic risk. Therefore, this study was aimed at comparing the effect of anesthesia on lung atelectasis observed through CT in clinically healthy cats and comparing the feasibility of non-anesthetic CT with non-anesthetic radiography in the detection of lung lesions in feline MGC. Thoracic CTs from anesthetized, clinically healthy cats and non-anesthetized either clinically healthy cats or MGC-affected cats were reviewed. In clinically healthy cats, motion artifacts and characteristics of lung atelectasis were observed and compared. In MGC-affected cats, motion artifacts were observed and compared to clinically healthy cats, and the number of MGC-affected cats, the number and characteristics of lung lesions were compared between non-anesthetic thoracic CT and radiography.

Results: Anesthesia significantly increased lung CT attenuation (P = 0.0047) and was significantly correlated with lung atelectasis (OR = 15; CI 2.02-111.18; P = 0.0081), particularly of the cranial lung lobe. Nonetheless, significantly higher motion artifacts in the caudal thoracic area were found in non-anesthetized healthy cats (P = 0.0146), but comparable low motion artifacts were observed in anesthetized healthy and MGC-affected cats. Non-anesthetic CT revealed higher numbers of MGC-affected cats and pulmonary nodules with a significantly lower nodular diameter (P = 0.0041) than those observed on radiographs. The smallest nodular diameters detected on radiographs and CT were 2.5 and 1.0 mm, respectively. Furthermore, CT showed additional information such as intra-thoracic lymphadenopathy, that could not be seen on radiographs.

Conclusions: Despite the motion artifacts, CT without anesthesia is a sensitive technique as it provides better lung inflation. Furthermore, compared to non-anesthetic radiography, non-anesthetic CT provided more information such as higher number of pulmonary nodules of a smaller size, including more distinct intra-thoracic lesions, such as lymphadenopathy, in MGC-affected cats.

Keywords: Atelectasis; Cat; Computed tomography; Lung; Mammary gland carcinoma; Radiography.

Fig. 1

A left lateral thoracic radiograph (A) and transverse computed tomographic image (B and C) of a mammary gland carcinoma affected cat. On radiograph (A), non-distinct ill-defined pulmonary nodules were found throughout the right inflated lung lobe. However, on transverse computed tomographic image (B and C), all pulmonary nodules, especially at the cranial thoracic compartment as seen on the thoracic radiograph (dash box, A) revealed clearly nodal margination (arrows)

Fig. 2

Ventrodorsal (A) and right lateral (C) thoracic radiographs and dorsal (B) and transverse (D) computed tomographic images of a mammary gland carcinoma affected cat. On thoracic radiograph (A and C), a focal, patchy lung consolidation was found at the left caudal lung lobe (arrows). However, on transverse computed tomographic images (B and D), the location of affected lung parenchyma was revealed as the lobar atelectatic area (arrows)