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Presented for intermittent lethargy for the past 2 months that acutely worsened over the past week. Per the owner, the patient had lost a significant amount of weight over the past 2 years.
Past pertinent medical history includes well controlled feline asthma (daily Fluticasone inhaler) and a recent diagnosis of mild pulmonary hypertension suspected secondary to pulmonary disease.
An abdominal ultrasound was performed at the referring veterinarian to isolate a cause for weight loss and lethargy. The findings of the ultrasound were consistent with inflammatory bowel disease versus small cell lymphoma. Additionally, a cavitary pulmonary mass was identified in the right caudal thorax. Thoracic radiographs were obtained and the patient was sent for referral.
On presentation, the patient was bright, alert and responsive with a normal temperature and heart rate. A moderate increase in respiratory rate (68 bpm) was thought to be exacerbated by stress of handling. The lungs auscultated with mild crackles, but the examination was otherwise unremarkable. The patient weighed 4.5 kg.
CT of the thorax, lung window
Thorax CT, soft tissue window
Thoracic CT, post-contrast, soft tissue window, transverse plane
Thoracic CT, post-contrast, soft tissue window, dorsal plane reconstruction
CT: 64 slice Toshiba Aquilion
– Thoracic CT before and after contrast administration
– Transverse lung algorithm, soft tissue algorithm (ST) pre and post
– Dorsal and sagittal reformatted images in lung, and post contrast ST
– 3 mm slice thickness
In the right caudal lung lobe, there is a large (4-5 cm diameter), rim enhancing, soft-tissue attenuating (HU approximately 30 on post contrast) mass. The central aspect of the mass is non-enhancing. Amorphous mineral densities are in the right ventrolateral aspect of the mass. The mass variably displaces and compresses the right caudal lobar artery and bronchus dorsomedially. A portion of the dorsomedial aspect of the right caudal lung lobe is atelectatic. There is no regional vascular invasion. Diffusely throughout the remaining lung lobes, the bronchial walls are thick.
Throughout all lung lobes, there are variable accumulations of round to linear, endobronchial mineral-attenuating foci. These endobronchial mineral densities have a somewhat linear and branching course. In some of the lung lobes, there is lobular, non-enhancing soft tissue attenuation admixed with the mineral densities, worse in the left cranial lobe. The right cranial lobar bronchus is pathologically dilated until the mid-aspect of the lobe with variable amounts of non-enhancing luminal soft-tissue attenuation. Scant pleural effusion surrounds the right caudal lung lobe. No tracheobronchial lymphadenopathy is present. Two cranial mediastinal lymph nodes are mildly enlarged. The cranial abdomen is normal. A ring artifact is most evident on the transverse lung algorithm.
Differential Diagnosis
The primary differential diagnosis considered was feline asthma, concurrent broncholithiasis and a right caudal lung lobe abscess. A pulmonary neoplasm (e.g. adenocarcinoma) with bronchial metastasis was considered less likely.
Based on the CT features of the mass and remaining lung parenchyma, a more benign process was considered. The patient had a right caudal lung lobectomy performed and recovered well.
Grossly, a large volume of purulent material drained from the lobe. The histopathologic diagnosis was marked bronchiectasis with rupture and regional chronic necrotizing and suppurative pneumonia. The mineral attenuating foci were documented as mineral concretions and support the imaging suspicion for broncholithiasis.
Bronchiectasis is characterized by abnormal, irreversible dilation of airways from chronic inflammation and damage to the bronchial walls. This results in pooling of mucus and exudates in the distal airways predisposing patients to secondary infections. Secondary infections elicit an inflammatory response that further destroys bronchial walls leading to a vicious, irreversible cycle. Congenital (e.g. primary ciliary dyskinesia) and acquired (e.g. diffuse inflammatory airway disease, obstructive neoplasia and bronchopneumonia) causes have been described.
A recent case series described bronchiectasis in cats. Bronchiectasis appeared to be an uncommon respiratory tract disorder predominantly affecting older male cats. Siamese cats were overrepresented. Unexpectedly, a little less than half the patients had a cough at presentation despite 7/12 cats having diffuse inflammatory airway disease.
Broncholithiasis is a pathologic condition when either calcified or ossified material is present within the bronchial lumen. Few reports of broncholithiasis exist in the veterinary literature, but recent reports suggest the likely mechanism of development is dystrophic mineralization of inspissated airway exudates secondary to chronic inflammatory airway disease. The marked bronchiectasis in the right caudal lung lobe contained non-enhancing soft-tissue attenuating and not fluid-attenuating material. This was expected as the CT attenuation of mucus and purulent debris is typically that of soft tissue. The severe enlargement of the fluid cavity in the right lobe was a bit unusual for bronchiectasis and therefore pulmonary abscess may be a more relevant term. This fluid-filled cavity lacked intralesional gas and lacked a thick rim as expected for an abscess. The broncholiths were mineral dense and had an arboreal course. The non-enhancing, soft-tissue attenuating bronchial material was likely intraluminal plugs of mucopurulent cellular debris.
The patient in this report had CT, radiographic and histopathologic evidence of chronic lower airway inflammation, broncholithiasis and bronchiectasis. Chronic lower airway inflammation likely played an important role in this patient. Widespread inflammation causes bronchoconstriction, airway wall inflammation, edema and mucus plugging. Bronchiectasis was a likely sequela. The broncholiths likely formed as mineralization of intraluminal exudative aggregates. Broncholiths may also predispose patients to broncho-obstruction and secondary bronchiectasis. Bronchiectasis has been described in a cat with miliary broncholithiasis.
References:
1) Bryne P, Berman J, Allan G, et al. CT findings in two cats with broncholithiasis. J Feline Med Surg 2016; 1-6.
2) Norris C, Samii V. Clinical, radiographic, and pathologic features of bronchiectasis in cats: 12 cases (1987-1999). JAVMA 2000; 4, 530-534.
3) Talavera J, et al. Case Report: Bronchilithiasis in a cat: clinical findings, long-term evolution and histopathological features. J Feline Med Surg 2008; 10, 95-101.