Computed tomography of thoracic lymph nodes in 100 dogs with no abnormalities in the dominated area

Evaluation of mediastinoscopy for cranial mediastinal and tracheobronchial lymphadenectomy in canine cadavers

OBJECTIVE

To report technical feasibility and describe procedural details of a novel single incision minimally invasive approach to the mediastinum in cadaver dogs.

STUDY DESIGN

Cadaveric study.

ANIMALS

Large breed (25-40 kg) cadaver dogs (n = 10).

METHODS

Three of 10 cadavers were used for preliminary technique development without data recording. Cadaver specimens underwent pre- and postoperative thoracic computed tomographic scans. Seven dogs were placed in dorsal recumbency and mediastinoscopy was performed via a SILS port placed cranial to the thoracic inlet with CO2 insufflation of the mediastinum at 2-4 mmHg. Retrieval of all CT and visually identified mediastinal lymph nodes (LN) was attempted; endoscopic compartmental and individual LN dissection times and subjective operative challenges were recorded. Procedural success scores for visualization and dissection as well as NASA-task force index scores were recorded per lymph node, per cadaver.

RESULTS

Median time required for initial approach including SILS placement was 5 min (range 5-10 min). Individual LN retrieval times ranged from 2 to 32 min. Mediastinoscopic retrieval of LNs was most commonly successful for the left tracheobronchial LN (7/7), followed by the right tracheobronchial LN (4/7), the left and right sternal LNs (3/7 each), and the cranial mediastinal LNs (1/7). Post-procedure pleural gas was identified on CT in 4/7 cadavers.

CONCLUSIONS

Mediastinoscopy as reported was feasible in large breed canine cadavers and retrieval or cup biopsy of a variety of lymph nodes is possible from the described approach. Application in living animals and its associated challenges should be further investigated.

CLINICAL SIGNIFICANCE

Mediastinoscopy may provide a novel minimally invasive approach to the evaluation and oncologic staging of the cranial mediastinum in dogs.

Correlation between computed tomography and histological evaluation of nodal metastasis in dogs with mast cell tumours

Early diagnosis of nodal metastasis has been shown to impact prognosis for dogs with mast cell tumours (MCT). The objective of this retrospective study was to determine the correlation between computed tomographic characteristics of lymph nodes and histologic nodal metastasis using the HN classification system, in dogs with cutaneous or subcutaneous MCT and regional lymph node(s) removal. Dogs that had removal of MCT and regional lymphadenectomy within 31 days of the initial staging computed tomography (CT) were enrolled. Subjective lymph node characteristics used included margination, loss of fat at hilus, shape of margin, perinodal fat pattern, increase in number of nodes, and pre- and post-contrast heterogeneity. Enhancement, heterogeneity, and short-long axis ratio were calculated. Seventy-one lymph nodes from 37 dogs were included. Generalised linear mixed model of assessment of lymph node was performed twice, with binary outcome [non-metastatic (HN0/1) versus metastatic (HN2/3)] and 4-point scales (HN0-HN3). After blind assessment of 7 characteristics described above, a final subjective interpretation of each lymph node as non-metastatic or metastatic was assigned. A significant correlation was found between final interpretation and prediction of metastasis. Higher HN classification was also significantly correlated with the increased number of nodes and pre- and post-contrast heterogeneity. No correlation was found in short-long axis ratio, calculated heterogeneity, or degree of enhancement. Sensitivity of CT was 35.7%, specificity was 96.6%, and accuracy was 60.5% for nodal metastasis. CT alone cannot be recommended for assessment of metastasis. The use of multiple computed tomographic characteristics may increase accuracy of nodal metastasis detection.

Presumed residual thymic tissue is a common finding in thoracic computed tomography in adult dogs

Residual thymic tissue is a common incidental finding in thoracic CT of human adults. To determine whether presumed residual thymic tissue is also a common incidental finding in adult dogs, a two part-study was performed. The first part was a prospective, descriptive design where CT examination was performed in six canine cadavers within 24 h after death and presumed residual thymic tissue was examined pathologically. The second part of the study was a retrospective, analytical design where medical records of our institution were searched for thoracic CT scans of adult dogs performed in the year 2020. Age, sex, breed, presence of presumed thymic tissue, location, shape, attenuation, homogeneity, and width of the tissue were recorded and comparisons were performed using these data. In 4 of 6 of the prospective cases, thymic tissue was present on histology and in 2 of 6 dogs the presence of thymic tissue could not be confirmed. For the retrospective study, in 161/169 (95.3%) cases with presumed residual thymic tissue were detected. Shape and size were highly variable with either homogeneous (46.6%), heterogeneous (42.9%), or mixed (10.6%) attenuation. Dogs with presumed residual thymic tissue were significantly younger (median: 9.1 years; range: 1.2-14.3 vs. median: 10.5 years; range: 9.4-12.3) as were dogs with homogeneous attenuation of the tissue (median: 8.1 years; range: 1.2-14.3 vs. median: 9.5 years; range: 4.0-14.3). In conclusion, results indicated that presumed residual thymic tissue is a common CT finding in adult dogs and can be considered incidental.

Computed tomographic findings and clinical features in dogs with canine cutaneous lymphoma: 10 cases (2007-2018)

OBJECTIVE

To report clinical features, CT findings, treatment protocols, and outcomes for dogs in which canine cutaneous lymphoma (CCL) was diagnosed.

ANIMALS

10 client-owned dogs with CCL.

PROCEDURES

Medical records of dogs in which a diagnosis of CCL had been made between September 2007 and July 2018 and in which CT had been performed prior to treatment were reviewed. All available CT studies were reviewed, and an anatomical reference system was developed to map observed lesions. Treatment protocols and patient outcomes were summarized.

RESULTS

14 CT examinations were performed on the 10 dogs, and 9 dogs had lesions consistent with CCL on CT images. Nodular lesions were present in 8 dogs, and cutaneous or subcutaneous mass lesions were seen in 3. Well-defined, diffusely distributed, contrast-enhancing, cutaneous or subcutaneous nodules were most common; mass lesions were more variable in appearance. Nine dogs had lymphadenopathy, with the mandibular and axillary lymph nodes most commonly affected. Four dogs had confirmed nodal involvement, and 4 had confirmed visceral involvement. Nine dogs received treatment with chemotherapy, and 5 had a complete response.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that dogs with CCL may have a wide spectrum of CT findings. Many of these lesions, including affected lymph nodes, would be unlikely to be detected clinically, suggesting that CT may be a useful modality to assess the severity of disease and for guiding selection of local versus systemic treatment.